literature review on case study

Organizing Your Social Sciences Research Paper: Writing a Case Study

• Purpose of Guide
• Design Flaws to Avoid
• Independent and Dependent Variables
• Glossary of Research Terms
• Narrowing a Topic Idea
• Broadening a Topic Idea
• Extending the Timeliness of a Topic Idea
• Academic Writing Style
• Choosing a Title
• Making an Outline
• Paragraph Development
• Executive Summary
• The C.A.R.S. Model
• Background Information
• The Research Problem/Question
• Theoretical Framework
• Citation Tracking
• Content Alert Services
• Evaluating Sources
• Reading Research Effectively
• Primary Sources
• Secondary Sources
• Tiertiary Sources
• What Is Scholarly vs. Popular?
• Qualitative Methods
• Quantitative Methods
• Using Non-Textual Elements
• Limitations of the Study
• Common Grammar Mistakes
• Writing Concisely
• Avoiding Plagiarism
• Footnotes or Endnotes?
• Further Readings
• Annotated Bibliography
• Dealing with Nervousness
• Using Visual Aids
• Grading Someone Else's Paper
• Types of Structured Group Activities
• Group Project Survival Skills
• Multiple Book Review Essay
• Reviewing Collected Essays
• Writing a Case Study
• About Informed Consent
• Writing Field Notes
• Writing a Policy Memo
• Writing a Research Proposal
• Bibliography

The term case study refers to both a method of analysis and a specific research design for examining a problem, both of which are used in most circumstances to generalize across populations. This tab focuses on the latter--how to design and organize a research paper in the social sciences that analyzes a specific case.

A case study research paper examines a person, place, event, phenomenon, or other type of subject of analysis in order to extrapolate  key themes and results that help predict future trends, illuminate previously hidden issues that can be applied to practice, and/or provide a means for understanding an important research problem with greater clarity. A case study paper usually examines a single subject of analysis, but case study papers can also be designed as a comparative investigation that shows relationships between two or among more than two subjects. The methods used to study a case can rest within a quantitative, qualitative, or mixed-method investigative paradigm.

Case Studies . Writing@CSU. Colorado State University; Mills, Albert J. , Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010 ; “What is a Case Study?” In Swanborn, Peter G. Case Study Research: What, Why and How? London: SAGE, 2010.

How to Approach Writing a Case Study Research Paper

General information about how to choose a topic to investigate can be found under the " Choosing a Research Problem " tab in this writing guide. Review this page because it may help you identify a subject of analysis that can be investigated using a single case study design.

However, identifying a case to investigate involves more than choosing the research problem . A case study encompasses a problem contextualized around the application of in-depth analysis, interpretation, and discussion, often resulting in specific recommendations for action or for improving existing conditions. As Seawright and Gerring note, practical considerations such as time and access to information can influence case selection, but these issues should not be the sole factors used in describing the methodological justification for identifying a particular case to study. Given this, selecting a case includes considering the following:

• Does the case represent an unusual or atypical example of a research problem that requires more in-depth analysis? Cases often represent a topic that rests on the fringes of prior investigations because the case may provide new ways of understanding the research problem. For example, if the research problem is to identify strategies to improve policies that support girl's access to secondary education in predominantly Muslim nations, you could consider using Azerbaijan as a case study rather than selecting a more obvious nation in the Middle East. Doing so may reveal important new insights into recommending how governments in other predominantly Muslim nations can formulate policies that support improved access to education for girls.
• Does the case provide important insight or illuminate a previously hidden problem? In-depth analysis of a case can be based on the hypothesis that the case study will reveal trends or issues that have not been exposed in prior research or will reveal new and important implications for practice. For example, anecdotal evidence may suggest drug use among homeless veterans is related to their patterns of travel throughout the day. Assuming prior studies have not looked at individual travel choices as a way to study access to illicit drug use, a case study that observes a homeless veteran could reveal how issues of personal mobility choices facilitate regular access to illicit drugs. Note that it is important to conduct a thorough literature review to ensure that your assumption about the need to reveal new insights or previously hidden problems is valid and evidence-based.
• Does the case challenge and offer a counter-point to prevailing assumptions? Over time, research on any given topic can fall into a trap of developing assumptions based on outdated studies that are still applied to new or changing conditions or the idea that something should simply be accepted as "common sense," even though the issue has not been thoroughly tested in practice. A case may offer you an opportunity to gather evidence that challenges prevailing assumptions about a research problem and provide a new set of recommendations applied to practice that have not been tested previously. For example, perhaps there has been a long practice among scholars to apply a particular theory in explaining the relationship between two subjects of analysis. Your case could challenge this assumption by applying an innovative theoretical framework [perhaps borrowed from another discipline] to the study a case in order to explore whether this approach offers new ways of understanding the research problem. Taking a contrarian stance is one of the most important ways that new knowledge and understanding develops from existing literature.
• Does the case provide an opportunity to pursue action leading to the resolution of a problem? Another way to think about choosing a case to study is to consider how the results from investigating a particular case may result in findings that reveal ways in which to resolve an existing or emerging problem. For example, studying the case of an unforeseen incident, such as a fatal accident at a railroad crossing, can reveal hidden issues that could be applied to preventative measures that contribute to reducing the chance of accidents in the future. In this example, a case study investigating the accident could lead to a better understanding of where to strategically locate additional signals at other railroad crossings in order to better warn drivers of an approaching train, particularly when visibility is hindered by heavy rain, fog, or at night.
• Does the case offer a new direction in future research? A case study can be used as a tool for exploratory research that points to a need for further examination of the research problem. A case can be used when there are few studies that help predict an outcome or that establish a clear understanding about how best to proceed in addressing a problem. For example, after conducting a thorough literature review [very important!], you discover that little research exists showing the ways in which women contribute to promoting water conservation in rural communities of Uganda. A case study of how women contribute to saving water in a particular village can lay the foundation for understanding the need for more thorough research that documents how women in their roles as cooks and family caregivers think about water as a valuable resource within their community throughout rural regions of east Africa. The case could also point to the need for scholars to apply feminist theories of work and family to the issue of water conservation.

Eisenhardt, Kathleen M. “Building Theories from Case Study Research.” Academy of Management Review 14 (October 1989): 532-550; Emmel, Nick. Sampling and Choosing Cases in Qualitative Research: A Realist Approach . Thousand Oaks, CA: SAGE Publications, 2013; Gerring, John. “What Is a Case Study and What Is It Good for?” American Political Science Review 98 (May 2004): 341-354; Mills, Albert J. , Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010; Seawright, Jason and John Gerring. "Case Selection Techniques in Case Study Research." Political Research Quarterly 61 (June 2008): 294-308.

Structure and Writing Style

The purpose of a paper in the social sciences designed around a case study is to thoroughly investigate a subject of analysis in order to reveal a new understanding about the research problem and, in so doing, contributing new knowledge to what is already known from previous studies. In applied social sciences disciplines [e.g., education, social work, public administration, etc.], case studies may also be used to reveal best practices, highlight key programs, or investigate interesting aspects of professional work. In general, the structure of a case study research paper is not all that different from a standard college-level research paper. However, there are subtle differences you should be aware of. Here are the key elements to organizing and writing a case study research paper.

I.  Introduction

As with any research paper, your introduction should serve as a roadmap for your readers to ascertain the scope and purpose of your study . The introduction to a case study research paper, however, should not only describe the research problem and its significance, but you should also succinctly describe why the case is being used and how it relates to addressing the problem. The two elements should be linked. With this in mind, a good introduction answers these four questions:

• What was I studying? Describe the research problem and describe the subject of analysis you have chosen to address the problem. Explain how they are linked and what elements of the case will help to expand knowledge and understanding about the problem.
• Why was this topic important to investigate? Describe the significance of the research problem and state why a case study design and the subject of analysis that the paper is designed around is appropriate in addressing the problem.
• What did we know about this topic before I did this study? Provide background that helps lead the reader into the more in-depth literature review to follow. If applicable, summarize prior case study research applied to the research problem and why it fails to adequately address the research problem. Describe why your case will be useful. If no prior case studies have been used to address the research problem, explain why you have selected this subject of analysis.
• How will this study advance new knowledge or new ways of understanding? Explain why your case study will be suitable in helping to expand knowledge and understanding about the research problem.

Each of these questions should be addressed in no more than a few paragraphs. Exceptions to this can be when you are addressing a complex research problem or subject of analysis that requires more in-depth background information.

II.  Literature Review

The literature review for a case study research paper is generally structured the same as it is for any college-level research paper. The difference, however, is that the literature review is focused on providing background information and  enabling historical interpretation of the subject of analysis in relation to the research problem the case is intended to address . This includes synthesizing studies that help to:

• Place relevant works in the context of their contribution to understanding the case study being investigated . This would include summarizing studies that have used a similar subject of analysis to investigate the research problem. If there is literature using the same or a very similar case to study, you need to explain why duplicating past research is important [e.g., conditions have changed; prior studies were conducted long ago, etc.].
• Describe the relationship each work has to the others under consideration that informs the reader why this case is applicable . Your literature review should include a description of any works that support using the case to study the research problem and the underlying research questions.
• Identify new ways to interpret prior research using the case study . If applicable, review any research that has examined the research problem using a different research design. Explain how your case study design may reveal new knowledge or a new perspective or that can redirect research in an important new direction.
• Resolve conflicts amongst seemingly contradictory previous studies . This refers to synthesizing any literature that points to unresolved issues of concern about the research problem and describing how the subject of analysis that forms the case study can help resolve these existing contradictions.
• Point the way in fulfilling a need for additional research . Your review should examine any literature that lays a foundation for understanding why your case study design and the subject of analysis around which you have designed your study may reveal a new way of approaching the research problem or offer a perspective that points to the need for additional research.
• Expose any gaps that exist in the literature that the case study could help to fill . Summarize any literature that not only shows how your subject of analysis contributes to understanding the research problem, but how your case contributes to a new way of understanding the problem that prior research has failed to do.
• Locate your own research within the context of existing literature [very important!] . Collectively, your literature review should always place your case study within the larger domain of prior research about the problem. The overarching purpose of reviewing pertinent literature in a case study paper is to demonstrate that you have thoroughly identified and synthesized prior studies in the context of explaining the relevance of the case in addressing the research problem.

III.  Method

In this section, you explain why you selected a particular subject of analysis to study and the strategy you used to identify and ultimately decide that your case was appropriate in addressing the research problem. The way you describe the methods used varies depending on the type of subject of analysis that frames your case study.

If your subject of analysis is an incident or event . In the social and behavioral sciences, the event or incident that represents the case to be studied is usually bounded by time and place, with a clear beginning and end and with an identifiable location or position relative to its surroundings. The subject of analysis can be a rare or critical event or it can focus on a typical or regular event. The purpose of studying a rare event is to illuminate new ways of thinking about the broader research problem or to test a hypothesis. Critical incident case studies must describe the method by which you identified the event and explain the process by which you determined the validity of this case to inform broader perspectives about the research problem or to reveal new findings. However, the event does not have to be a rare or uniquely significant to support new thinking about the research problem or to challenge an existing hypothesis. For example, Walo, Bull, and Breen conducted a case study to identify and evaluate the direct and indirect economic benefits and costs of a local sports event in the City of Lismore, New South Wales, Australia. The purpose of their study was to provide new insights from measuring the impact of a typical local sports event that prior studies could not measure well because they focused on large "mega-events." Whether the event is rare or not, the methods section should include an explanation of the following characteristics of the event: a) when did it take place; b) what were the underlying circumstances leading to the event; c) what were the consequences of the event.

If your subject of analysis is a person. Explain why you selected this particular individual to be studied and describe what experience he or she has had that provides an opportunity to advance new understandings about the research problem. Mention any background about this person which might help the reader understand the significance of his/her experiences that make them worthy of study. This includes describing the relationships this person has had with other people, institutions, and/or events that support using him or her as the subject for a case study research paper. It is particularly important to differentiate the person as the subject of analysis from others and to succinctly explain how the person relates to examining the research problem.

If your subject of analysis is a place. In general, a case study that investigates a place suggests a subject of analysis that is unique or special in some way and that this uniqueness can be used to build new understanding or knowledge about the research problem. A case study of a place must not only describe its various attributes relevant to the research problem [e.g., physical, social, cultural, economic, political, etc.], but you must state the method by which you determined that this place will illuminate new understandings about the research problem. It is also important to articulate why a particular place as the case for study is being used if similar places also exist [i.e., if you are studying patterns of homeless encampments of veterans in open spaces, why study Echo Park in Los Angeles rather than Griffith Park?]. If applicable, describe what type of human activity involving this place makes it a good choice to study [e.g., prior research reveals Echo Park has more homeless veterans].

If your subject of analysis is a phenomenon. A phenomenon refers to a fact, occurrence, or circumstance that can be studied or observed but with the cause or explanation to be in question. In this sense, a phenomenon that forms your subject of analysis can encompass anything that can be observed or presumed to exist but is not fully understood. In the social and behavioral sciences, the case usually focuses on human interaction within a complex physical, social, economic, cultural, or political system. For example, the phenomenon could be the observation that many vehicles used by ISIS fighters are small trucks with English language advertisements on them. The research problem could be that ISIS fighters are difficult to combat because they are highly mobile. The research questions could be how and by what means are these vehicles used by ISIS being supplied to the militants and how might supply lines to these vehicles be cut? How might knowing the suppliers of these trucks from overseas reveal larger networks of collaborators and financial support? A case study of a phenomenon most often encompasses an in-depth analysis of a cause and effect that is grounded in an interactive relationship between people and their environment in some way.

NOTE:   The choice of the case or set of cases to study cannot appear random. Evidence that supports the method by which you identified and chose your subject of analysis should be linked to the findings from the literature review. Be sure to cite any prior studies that helped you determine that the case you chose was appropriate for investigating the research problem.

IV.  Discussion

The main elements of your discussion section are generally the same as any research paper, but centered around interpreting and drawing conclusions about the key findings from your case study. Note that a general social sciences research paper may contain a separate section to report findings. However, in a paper designed around a case study, it is more common to combine a description of the findings with the discussion about their implications. The objectives of your discussion section should include the following:

Reiterate the Research Problem/State the Major Findings Briefly reiterate the research problem you are investigating and explain why the subject of analysis around which you designed the case study were used. You should then describe the findings revealed from your study of the case using direct, declarative, and succinct proclamation of the study results. Highlight any findings that were unexpected or especially profound.

Explain the Meaning of the Findings and Why They are Important Systematically explain the meaning of your case study findings and why you believe they are important. Begin this part of the section by repeating what you consider to be your most important or surprising finding first, then systematically review each finding. Be sure to thoroughly extrapolate what your analysis of the case can tell the reader about situations or conditions beyond the actual case that was studied while, at the same time, being careful not to misconstrue or conflate a finding that undermines the external validity of your conclusions.

Relate the Findings to Similar Studies No study in the social sciences is so novel or possesses such a restricted focus that it has absolutely no relation to previously published research. The discussion section should relate your case study results to those found in other studies, particularly if questions raised from prior studies served as the motivation for choosing your subject of analysis. This is important because comparing and contrasting the findings of other studies helps to support the overall importance of your results and it highlights how and in what ways your case study design and the subject of analysis differs from prior research about the topic.

Consider Alternative Explanations of the Findings It is important to remember that the purpose of social science research is to discover and not to prove. When writing the discussion section, you should carefully consider all possible explanations for the case study results, rather than just those that fit your hypothesis or prior assumptions and biases. Be alert to what the in-depth analysis of the case may reveal about the research problem, including offering a contrarian perspective to what scholars have stated in prior research.

Acknowledge the Study's Limitations You can state the study's limitations in the conclusion section of your paper but describing the limitations of your subject of analysis in the discussion section provides an opportunity to identify the limitations and explain why they are not significant. This part of the discussion section should also note any unanswered questions or issues your case study could not address. More detailed information about how to document any limitations to your research can be found here .

Suggest Areas for Further Research Although your case study may offer important insights about the research problem, there are likely additional questions related to the problem that remain unanswered or findings that unexpectedly revealed themselves as a result of your in-depth analysis of the case. Be sure that the recommendations for further research are linked to the research problem and that you explain why your recommendations are valid in other contexts and based on the original assumptions of your study.

V.  Conclusion

As with any research paper, you should summarize your conclusion in clear, simple language; emphasize how the findings from your case study differs from or supports prior research and why. Do not simply reiterate the discussion section. Provide a synthesis of key findings presented in the paper to show how these converge to address the research problem. If you haven't already done so in the discussion section, be sure to document the limitations of your case study and needs for further research.

The function of your paper's conclusion is to: 1)  restate the main argument supported by the findings from the analysis of your case; 2) clearly state the context, background, and necessity of pursuing the research problem using a case study design in relation to an issue, controversy, or a gap found from reviewing the literature; and, 3) provide a place for you to persuasively and succinctly restate the significance of your research problem, given that the reader has now been presented with in-depth information about the topic.

Consider the following points to help ensure your conclusion is appropriate:

• If the argument or purpose of your paper is complex, you may need to summarize these points for your reader.
• If prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the conclusion of your paper to describe your main points and explain their significance.
• Move from a detailed to a general level of consideration of the case study's findings that returns the topic to the context provided by the introduction or within a new context that emerges from your case study findings.

Note that, depending on the discipline you are writing in and your professor's preferences, the concluding paragraph may contain your final reflections on the evidence presented applied to practice or on the essay's central research problem. However, the nature of being introspective about the subject of analysis you have investigated will depend on whether you are explicitly asked to express your observations in this way.

Problems to Avoid

Overgeneralization One of the goals of a case study is to lay a foundation for understanding broader trends and issues applied to similar circumstances. However, be careful when drawing conclusions from your case study. They must be evidence-based and grounded in the results of the study; otherwise, it is merely speculation. Looking at a prior example, it would be incorrect to state that a factor in improving girls access to education in Azerbaijan and the policy implications this may have for improving access in other Muslim nations is due to girls access to social media if there is no documentary evidence from your case study to indicate this. There may be anecdotal evidence that retention rates were better for girls who were on social media, but this observation would only point to the need for further research and would not be a definitive finding if this was not a part of your original research agenda.

Failure to Document Limitations No case is going to reveal all that needs to be understood about a research problem. Therefore, just as you have to clearly state the limitations of a general research study , you must describe the specific limitations inherent in the subject of analysis. For example, the case of studying how women conceptualize the need for water conservation in a village in Uganda could have limited application in other cultural contexts or in areas where fresh water from rivers or lakes is plentiful and, therefore, conservation is understood differently than preserving access to a scarce resource.

Failure to Extrapolate All Possible Implications Just as you don't want to over-generalize from your case study findings, you also have to be thorough in the consideration of all possible outcomes or recommendations derived from your findings. If you do not, your reader may question the validity of your analysis, particularly if you failed to document an obvious outcome from your case study research. For example, in the case of studying the accident at the railroad crossing to evaluate where and what types of warning signals should be located, you failed to take into consideration speed limit signage as well as warning signals. When designing your case study, be sure you have thoroughly addressed all aspects of the problem and do not leave gaps in your analysis.

Case Studies . Writing@CSU. Colorado State University; Gerring, John. Case Study Research: Principles and Practices . New York: Cambridge University Press, 2007; Merriam, Sharan B. Qualitative Research and Case Study Applications in Education . Rev. ed. San Francisco, CA: Jossey-Bass, 1998; Miller, Lisa L. “The Use of Case Studies in Law and Social Science Research.” Annual Review of Law and Social Science 14 (2018): TBD; Mills, Albert J., Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010; Putney, LeAnn Grogan. "Case Study." In Encyclopedia of Research Design , Neil J. Salkind, editor. (Thousand Oaks, CA: SAGE Publications, 2010), pp. 116-120; Simons, Helen. Case Study Research in Practice . London: SAGE Publications, 2009;  Kratochwill,  Thomas R. and Joel R. Levin, editors. Single-Case Research Design and Analysis: New Development for Psychology and Education .  Hilldsale, NJ: Lawrence Erlbaum Associates, 1992; Swanborn, Peter G. Case Study Research: What, Why and How? London : SAGE, 2010; Yin, Robert K. Case Study Research: Design and Methods . 6th edition. Los Angeles, CA, SAGE Publications, 2014; Walo, Maree, Adrian Bull, and Helen Breen. “Achieving Economic Benefits at Local Events: A Case Study of a Local Sports Event.” Festival Management and Event Tourism 4 (1996): 95-106.

Writing Tip

At Least Five Misconceptions about Case Study Research

Social science case studies are often perceived as limited in their ability to create new knowledge because they are not randomly selected and findings cannot be generalized to larger populations. Flyvbjerg examines five misunderstandings about case study research and systematically "corrects" each one. To quote, these are:

Misunderstanding 1 :  General, theoretical [context-independent knowledge is more valuable than concrete, practical (context-dependent) knowledge. Misunderstanding 2 :  One cannot generalize on the basis of an individual case; therefore, the case study cannot contribute to scientific development. Misunderstanding 3 :  The case study is most useful for generating hypotheses; that is, in the first stage of a total research process, whereas other methods are more suitable for hypotheses testing and theory building. Misunderstanding 4 :  The case study contains a bias toward verification, that is, a tendency to confirm the researcher’s preconceived notions. Misunderstanding 5 :  It is often difficult to summarize and develop general propositions and theories on the basis of specific case studies [p. 221].

While writing your paper, think introspectively about how you addressed these misconceptions because to do so can help you strengthen the validity and reliability of your research by clarifying issues of case selection, the testing and challenging of existing assumptions, the interpretation of key findings, and the summation of case outcomes. Think of a case study research paper as a complete, in-depth narrative about the specific properties and key characteristics of your subject of analysis applied to the research problem.

Flyvbjerg, Bent. “Five Misunderstandings About Case-Study Research.” Qualitative Inquiry 12 (April 2006): 219-245.

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What is a Literature Review? How to Write It (with Examples)

A literature review is a critical analysis and synthesis of existing research on a particular topic. It provides an overview of the current state of knowledge, identifies gaps, and highlights key findings in the literature. 1 The purpose of a literature review is to situate your own research within the context of existing scholarship, demonstrating your understanding of the topic and showing how your work contributes to the ongoing conversation in the field. Learning how to write a literature review is a critical tool for successful research. Your ability to summarize and synthesize prior research pertaining to a certain topic demonstrates your grasp on the topic of study, and assists in the learning process. 

Table of Contents

• What is the purpose of literature review? 
• a. Habitat Loss and Species Extinction: 
• b. Range Shifts and Phenological Changes: 
• c. Ocean Acidification and Coral Reefs: 
• d. Adaptive Strategies and Conservation Efforts: 

How to write a good literature review 

• Choose a Topic and Define the Research Question: 
• Decide on the Scope of Your Review: 
• Select Databases for Searches: 
• Conduct Searches and Keep Track: 
• Review the Literature: 
• Organize and Write Your Literature Review: 
• How to write a literature review faster with Paperpal? 
• Frequently asked questions 

What is a literature review?

A well-conducted literature review demonstrates the researcher’s familiarity with the existing literature, establishes the context for their own research, and contributes to scholarly conversations on the topic. One of the purposes of a literature review is also to help researchers avoid duplicating previous work and ensure that their research is informed by and builds upon the existing body of knowledge.

What is the purpose of literature review?

A literature review serves several important purposes within academic and research contexts. Here are some key objectives and functions of a literature review: 2  

1. Contextualizing the Research Problem: The literature review provides a background and context for the research problem under investigation. It helps to situate the study within the existing body of knowledge. 

2. Identifying Gaps in Knowledge: By identifying gaps, contradictions, or areas requiring further research, the researcher can shape the research question and justify the significance of the study. This is crucial for ensuring that the new research contributes something novel to the field. 

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3. Understanding Theoretical and Conceptual Frameworks: Literature reviews help researchers gain an understanding of the theoretical and conceptual frameworks used in previous studies. This aids in the development of a theoretical framework for the current research. 

4. Providing Methodological Insights: Another purpose of literature reviews is that it allows researchers to learn about the methodologies employed in previous studies. This can help in choosing appropriate research methods for the current study and avoiding pitfalls that others may have encountered. 

5. Establishing Credibility: A well-conducted literature review demonstrates the researcher’s familiarity with existing scholarship, establishing their credibility and expertise in the field. It also helps in building a solid foundation for the new research. 

6. Informing Hypotheses or Research Questions: The literature review guides the formulation of hypotheses or research questions by highlighting relevant findings and areas of uncertainty in existing literature. 

Literature review example

Let’s delve deeper with a literature review example: Let’s say your literature review is about the impact of climate change on biodiversity. You might format your literature review into sections such as the effects of climate change on habitat loss and species extinction, phenological changes, and marine biodiversity. Each section would then summarize and analyze relevant studies in those areas, highlighting key findings and identifying gaps in the research. The review would conclude by emphasizing the need for further research on specific aspects of the relationship between climate change and biodiversity. The following literature review template provides a glimpse into the recommended literature review structure and content, demonstrating how research findings are organized around specific themes within a broader topic. 

Literature Review on Climate Change Impacts on Biodiversity:

Climate change is a global phenomenon with far-reaching consequences, including significant impacts on biodiversity. This literature review synthesizes key findings from various studies: 

a. Habitat Loss and Species Extinction:

Climate change-induced alterations in temperature and precipitation patterns contribute to habitat loss, affecting numerous species (Thomas et al., 2004). The review discusses how these changes increase the risk of extinction, particularly for species with specific habitat requirements. 

b. Range Shifts and Phenological Changes:

Observations of range shifts and changes in the timing of biological events (phenology) are documented in response to changing climatic conditions (Parmesan & Yohe, 2003). These shifts affect ecosystems and may lead to mismatches between species and their resources. 

c. Ocean Acidification and Coral Reefs:

The review explores the impact of climate change on marine biodiversity, emphasizing ocean acidification’s threat to coral reefs (Hoegh-Guldberg et al., 2007). Changes in pH levels negatively affect coral calcification, disrupting the delicate balance of marine ecosystems. 

d. Adaptive Strategies and Conservation Efforts:

Recognizing the urgency of the situation, the literature review discusses various adaptive strategies adopted by species and conservation efforts aimed at mitigating the impacts of climate change on biodiversity (Hannah et al., 2007). It emphasizes the importance of interdisciplinary approaches for effective conservation planning. 

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Writing a literature review involves summarizing and synthesizing existing research on a particular topic. A good literature review format should include the following elements. 

Introduction: The introduction sets the stage for your literature review, providing context and introducing the main focus of your review. 

• Opening Statement: Begin with a general statement about the broader topic and its significance in the field. 
• Scope and Purpose: Clearly define the scope of your literature review. Explain the specific research question or objective you aim to address. 
• Organizational Framework: Briefly outline the structure of your literature review, indicating how you will categorize and discuss the existing research. 
• Significance of the Study: Highlight why your literature review is important and how it contributes to the understanding of the chosen topic. 
• Thesis Statement: Conclude the introduction with a concise thesis statement that outlines the main argument or perspective you will develop in the body of the literature review. 

Body: The body of the literature review is where you provide a comprehensive analysis of existing literature, grouping studies based on themes, methodologies, or other relevant criteria. 

• Organize by Theme or Concept: Group studies that share common themes, concepts, or methodologies. Discuss each theme or concept in detail, summarizing key findings and identifying gaps or areas of disagreement. 
• Critical Analysis: Evaluate the strengths and weaknesses of each study. Discuss the methodologies used, the quality of evidence, and the overall contribution of each work to the understanding of the topic. 
• Synthesis of Findings: Synthesize the information from different studies to highlight trends, patterns, or areas of consensus in the literature. 
• Identification of Gaps: Discuss any gaps or limitations in the existing research and explain how your review contributes to filling these gaps. 
• Transition between Sections: Provide smooth transitions between different themes or concepts to maintain the flow of your literature review. 

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Conclusion: The conclusion of your literature review should summarize the main findings, highlight the contributions of the review, and suggest avenues for future research. 

• Summary of Key Findings: Recap the main findings from the literature and restate how they contribute to your research question or objective. 
• Contributions to the Field: Discuss the overall contribution of your literature review to the existing knowledge in the field. 
• Implications and Applications: Explore the practical implications of the findings and suggest how they might impact future research or practice. 
• Recommendations for Future Research: Identify areas that require further investigation and propose potential directions for future research in the field. 
• Final Thoughts: Conclude with a final reflection on the importance of your literature review and its relevance to the broader academic community. 

Conducting a literature review

Conducting a literature review is an essential step in research that involves reviewing and analyzing existing literature on a specific topic. It’s important to know how to do a literature review effectively, so here are the steps to follow: 1  

Choose a Topic and Define the Research Question:

• Select a topic that is relevant to your field of study. 
• Clearly define your research question or objective. Determine what specific aspect of the topic do you want to explore? 

Decide on the Scope of Your Review:

• Determine the timeframe for your literature review. Are you focusing on recent developments, or do you want a historical overview? 
• Consider the geographical scope. Is your review global, or are you focusing on a specific region? 
• Define the inclusion and exclusion criteria. What types of sources will you include? Are there specific types of studies or publications you will exclude? 

Select Databases for Searches:

• Identify relevant databases for your field. Examples include PubMed, IEEE Xplore, Scopus, Web of Science, and Google Scholar. 
• Consider searching in library catalogs, institutional repositories, and specialized databases related to your topic. 

Conduct Searches and Keep Track:

• Develop a systematic search strategy using keywords, Boolean operators (AND, OR, NOT), and other search techniques. 
• Record and document your search strategy for transparency and replicability. 
• Keep track of the articles, including publication details, abstracts, and links. Use citation management tools like EndNote, Zotero, or Mendeley to organize your references. 

Review the Literature:

• Evaluate the relevance and quality of each source. Consider the methodology, sample size, and results of studies. 
• Organize the literature by themes or key concepts. Identify patterns, trends, and gaps in the existing research. 
• Summarize key findings and arguments from each source. Compare and contrast different perspectives. 
• Identify areas where there is a consensus in the literature and where there are conflicting opinions. 
• Provide critical analysis and synthesis of the literature. What are the strengths and weaknesses of existing research? 

Organize and Write Your Literature Review:

• Literature review outline should be based on themes, chronological order, or methodological approaches. 
• Write a clear and coherent narrative that synthesizes the information gathered. 
• Use proper citations for each source and ensure consistency in your citation style (APA, MLA, Chicago, etc.). 
• Conclude your literature review by summarizing key findings, identifying gaps, and suggesting areas for future research. 

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• Cite with Confidence: Paperpal makes it easy to incorporate relevant citations and references into your writing, ensuring your arguments are well-supported by credible sources. This translates to a polished, well-researched literature review. 

The literature review sample and detailed advice on writing and conducting a review will help you produce a well-structured report. But remember that a good literature review is an ongoing process, and it may be necessary to revisit and update it as your research progresses. By combining effortless research with an easy citation process, Paperpal Research streamlines the literature review process and empowers you to write faster and with more confidence. Try Paperpal Research now and see for yourself.  

Frequently asked questions

A literature review is a critical and comprehensive analysis of existing literature (published and unpublished works) on a specific topic or research question and provides a synthesis of the current state of knowledge in a particular field. A well-conducted literature review is crucial for researchers to build upon existing knowledge, avoid duplication of efforts, and contribute to the advancement of their field. It also helps researchers situate their work within a broader context and facilitates the development of a sound theoretical and conceptual framework for their studies.

Literature review is a crucial component of research writing, providing a solid background for a research paper’s investigation. The aim is to keep professionals up to date by providing an understanding of ongoing developments within a specific field, including research methods, and experimental techniques used in that field, and present that knowledge in the form of a written report. Also, the depth and breadth of the literature review emphasizes the credibility of the scholar in his or her field.  

Before writing a literature review, it’s essential to undertake several preparatory steps to ensure that your review is well-researched, organized, and focused. This includes choosing a topic of general interest to you and doing exploratory research on that topic, writing an annotated bibliography, and noting major points, especially those that relate to the position you have taken on the topic. 

Literature reviews and academic research papers are essential components of scholarly work but serve different purposes within the academic realm. 3 A literature review aims to provide a foundation for understanding the current state of research on a particular topic, identify gaps or controversies, and lay the groundwork for future research. Therefore, it draws heavily from existing academic sources, including books, journal articles, and other scholarly publications. In contrast, an academic research paper aims to present new knowledge, contribute to the academic discourse, and advance the understanding of a specific research question. Therefore, it involves a mix of existing literature (in the introduction and literature review sections) and original data or findings obtained through research methods. 

Literature reviews are essential components of academic and research papers, and various strategies can be employed to conduct them effectively. If you want to know how to write a literature review for a research paper, here are four common approaches that are often used by researchers.  Chronological Review: This strategy involves organizing the literature based on the chronological order of publication. It helps to trace the development of a topic over time, showing how ideas, theories, and research have evolved.  Thematic Review: Thematic reviews focus on identifying and analyzing themes or topics that cut across different studies. Instead of organizing the literature chronologically, it is grouped by key themes or concepts, allowing for a comprehensive exploration of various aspects of the topic.  Methodological Review: This strategy involves organizing the literature based on the research methods employed in different studies. It helps to highlight the strengths and weaknesses of various methodologies and allows the reader to evaluate the reliability and validity of the research findings.  Theoretical Review: A theoretical review examines the literature based on the theoretical frameworks used in different studies. This approach helps to identify the key theories that have been applied to the topic and assess their contributions to the understanding of the subject.  It’s important to note that these strategies are not mutually exclusive, and a literature review may combine elements of more than one approach. The choice of strategy depends on the research question, the nature of the literature available, and the goals of the review. Additionally, other strategies, such as integrative reviews or systematic reviews, may be employed depending on the specific requirements of the research.

The literature review format can vary depending on the specific publication guidelines. However, there are some common elements and structures that are often followed. Here is a general guideline for the format of a literature review:  Introduction:   Provide an overview of the topic.  Define the scope and purpose of the literature review.  State the research question or objective.  Body:   Organize the literature by themes, concepts, or chronology.  Critically analyze and evaluate each source.  Discuss the strengths and weaknesses of the studies.  Highlight any methodological limitations or biases.  Identify patterns, connections, or contradictions in the existing research.  Conclusion:   Summarize the key points discussed in the literature review.  Highlight the research gap.  Address the research question or objective stated in the introduction.  Highlight the contributions of the review and suggest directions for future research.

Both annotated bibliographies and literature reviews involve the examination of scholarly sources. While annotated bibliographies focus on individual sources with brief annotations, literature reviews provide a more in-depth, integrated, and comprehensive analysis of existing literature on a specific topic. The key differences are as follows: 

References 

• Denney, A. S., & Tewksbury, R. (2013). How to write a literature review.  Journal of criminal justice education ,  24 (2), 218-234. 
• Pan, M. L. (2016).  Preparing literature reviews: Qualitative and quantitative approaches . Taylor & Francis. 
• Cantero, C. (2019). How to write a literature review.  San José State University Writing Center . 

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• Case Study | Definition, Examples & Methods

Case Study | Definition, Examples & Methods

Published on 5 May 2022 by Shona McCombes . Revised on 30 January 2023.

A case study is a detailed study of a specific subject, such as a person, group, place, event, organisation, or phenomenon. Case studies are commonly used in social, educational, clinical, and business research.

A case study research design usually involves qualitative methods , but quantitative methods are sometimes also used. Case studies are good for describing , comparing, evaluating, and understanding different aspects of a research problem .

Table of contents

When to do a case study, step 1: select a case, step 2: build a theoretical framework, step 3: collect your data, step 4: describe and analyse the case.

A case study is an appropriate research design when you want to gain concrete, contextual, in-depth knowledge about a specific real-world subject. It allows you to explore the key characteristics, meanings, and implications of the case.

Case studies are often a good choice in a thesis or dissertation . They keep your project focused and manageable when you don’t have the time or resources to do large-scale research.

You might use just one complex case study where you explore a single subject in depth, or conduct multiple case studies to compare and illuminate different aspects of your research problem.

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Once you have developed your problem statement and research questions , you should be ready to choose the specific case that you want to focus on. A good case study should have the potential to:

• Provide new or unexpected insights into the subject
• Challenge or complicate existing assumptions and theories
• Propose practical courses of action to resolve a problem
• Open up new directions for future research

Unlike quantitative or experimental research, a strong case study does not require a random or representative sample. In fact, case studies often deliberately focus on unusual, neglected, or outlying cases which may shed new light on the research problem.

If you find yourself aiming to simultaneously investigate and solve an issue, consider conducting action research . As its name suggests, action research conducts research and takes action at the same time, and is highly iterative and flexible. 

However, you can also choose a more common or representative case to exemplify a particular category, experience, or phenomenon.

While case studies focus more on concrete details than general theories, they should usually have some connection with theory in the field. This way the case study is not just an isolated description, but is integrated into existing knowledge about the topic. It might aim to:

• Exemplify a theory by showing how it explains the case under investigation
• Expand on a theory by uncovering new concepts and ideas that need to be incorporated
• Challenge a theory by exploring an outlier case that doesn’t fit with established assumptions

To ensure that your analysis of the case has a solid academic grounding, you should conduct a literature review of sources related to the topic and develop a theoretical framework . This means identifying key concepts and theories to guide your analysis and interpretation.

There are many different research methods you can use to collect data on your subject. Case studies tend to focus on qualitative data using methods such as interviews, observations, and analysis of primary and secondary sources (e.g., newspaper articles, photographs, official records). Sometimes a case study will also collect quantitative data .

The aim is to gain as thorough an understanding as possible of the case and its context.

In writing up the case study, you need to bring together all the relevant aspects to give as complete a picture as possible of the subject.

How you report your findings depends on the type of research you are doing. Some case studies are structured like a standard scientific paper or thesis, with separate sections or chapters for the methods , results , and discussion .

Others are written in a more narrative style, aiming to explore the case from various angles and analyse its meanings and implications (for example, by using textual analysis or discourse analysis ).

In all cases, though, make sure to give contextual details about the case, connect it back to the literature and theory, and discuss how it fits into wider patterns or debates.

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• Steps in Conducting a Literature Review

What is a literature review?

A literature review is an integrated analysis -- not just a summary-- of scholarly writings and other relevant evidence related directly to your research question.  That is, it represents a synthesis of the evidence that provides background information on your topic and shows a association between the evidence and your research question.

A literature review may be a stand alone work or the introduction to a larger research paper, depending on the assignment.  Rely heavily on the guidelines your instructor has given you.

Why is it important?

A literature review is important because it:

• Explains the background of research on a topic.
• Demonstrates why a topic is significant to a subject area.
• Discovers relationships between research studies/ideas.
• Identifies major themes, concepts, and researchers on a topic.
• Identifies critical gaps and points of disagreement.
• Discusses further research questions that logically come out of the previous studies.

APA7 Style resources

APA Style Blog - for those harder to find answers

1. Choose a topic. Define your research question.

Your literature review should be guided by your central research question.  The literature represents background and research developments related to a specific research question, interpreted and analyzed by you in a synthesized way.

• Make sure your research question is not too broad or too narrow.  Is it manageable?
• Begin writing down terms that are related to your question. These will be useful for searches later.
• If you have the opportunity, discuss your topic with your professor and your class mates.

2. Decide on the scope of your review

How many studies do you need to look at? How comprehensive should it be? How many years should it cover? 

• This may depend on your assignment.  How many sources does the assignment require?

3. Select the databases you will use to conduct your searches.

Make a list of the databases you will search. 

Where to find databases:

• use the tabs on this guide
• Find other databases in the Nursing Information Resources web page
• More on the Medical Library web page
• ... and more on the Yale University Library web page

4. Conduct your searches to find the evidence. Keep track of your searches.

• Use the key words in your question, as well as synonyms for those words, as terms in your search. Use the database tutorials for help.
• Save the searches in the databases. This saves time when you want to redo, or modify, the searches. It is also helpful to use as a guide is the searches are not finding any useful results.
• Review the abstracts of research studies carefully. This will save you time.
• Use the bibliographies and references of research studies you find to locate others.
• Check with your professor, or a subject expert in the field, if you are missing any key works in the field.
• Ask your librarian for help at any time.
• Use a citation manager, such as EndNote as the repository for your citations. See the EndNote tutorials for help.

Review the literature

Some questions to help you analyze the research:

• What was the research question of the study you are reviewing? What were the authors trying to discover?
• Was the research funded by a source that could influence the findings?
• What were the research methodologies? Analyze its literature review, the samples and variables used, the results, and the conclusions.
• Does the research seem to be complete? Could it have been conducted more soundly? What further questions does it raise?
• If there are conflicting studies, why do you think that is?
• How are the authors viewed in the field? Has this study been cited? If so, how has it been analyzed?

Tips: 

• Review the abstracts carefully.  
• Keep careful notes so that you may track your thought processes during the research process.
• Create a matrix of the studies for easy analysis, and synthesis, across all of the studies.
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CC0006 Basics of Report Writing

Structure of a report (case study, literature review or survey).

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The information in the report has to be organised in the best possible way for the reader to understand the issue being investigated, analysis of the findings and recommendations or implications that relate directly to the findings. Given below are the main sections of a standard report. Click on each section heading to learn more about it.

• Tells the reader what the report is about
• Informative, short, catchy

Example - Sea level rise in Singapore : Causes, Impact and Solution

The title page must also include group name, group members and their matriculation numbers.

Content s Page

• Has headings and subheadings that show the reader where the various sections of the report are located
• Written on a separate page
• Includes the page numbers of each section
• Briefly summarises the report, the process of research and final conclusions
• Provides a quick overview of the report and describes the main highlights
• Short, usually not more than 150 words in length
• Mention briefly why you choose this project, what are the implications and what kind of problems it will solve

Usually, the abstract is written last, ie. after writing the other sections and you know the key points to draw out from these sections. Abstracts allow readers who may be interested in the report to decide whether it is relevant to their purposes.

Introduction

• Discusses the background and sets the context
• Introduces the topic, significance of the problem, and the purpose of research
• Gives the scope ie shows what it includes and excludes

In the introduction, write about what motivates your project, what makes it interesting, what questions do you aim to answer by doing your project. The introduction lays the foundation for understanding the research problem and should be written in a way that leads the reader from the general subject area of the topic to the particular topic of research.

Literature Review

• Helps to gain an understanding of the existing research in that topic
• To develop on your own ideas and build your ideas based on the existing knowledge
• Prevents duplication of the research done by others

Search the existing literature for information. Identify the data pertinent to your topic. Review, extract the relevant information for eg how the study was conducted and the findings. Summarise the information. Write what is already known about the topic and what do the sources that you have reviewed say. Identify conflicts in previous studies, open questions, or gaps that may exist. If you are doing

• Case study - look for background information and if any similar case studies have been done before.
• Literature review - find out from literature, what is the background to the questions that you are looking into
• Site visit - use the literature review to read up and prepare good questions before hand.
• Survey - find out if similar surveys have been done before and what did they find?

Keep a record of the source details of any information you want to use in your report so that you can reference them accurately.

Methodology

Methodology is the approach that you take to gather data and arrive at the recommendation(s). Choose a method that is appropriate for the research topic and explain it in detail.

In this section, address the following: a) How the data was collected b) How it was analysed and c) Explain or justify why a particular method was chosen.

Usually, the methodology is written in the past tense and can be in the passive voice. Some examples of the different methods that you can use to gather data are given below. The data collected provides evidence to build your arguments. Collect data, integrate the findings and perspectives from different studies and add your own analysis of its feasibility.

• Explore the literature/news/internet sources to know the topic in depth
• Give a description of how you selected the literature for your project
• Compare the studies, and highlight the findings, gaps or limitations.
• An in-depth, detailed examination of specific cases within a real-world context.
• Enables you to examine the data within a specific context.
• Examine a well defined case to identify the essential factors, process and relationship.
• Write the case description, the context and the process involved.
• Make sense of the evidence in the case(s) to answer the research question
• Gather data from a predefined group of respondents by asking relevant questions
• Can be conducted in person or online
• Why you chose this method (questionnaires, focus group, experimental procedure, etc)
• How you carried out the survey. Include techniques and any equipment you used
• If there were participants in your research, who were they? How did you select them and how may were there?
• How the survey questions address the different aspects of the research question
• Analyse the technology / policy approaches by visiting the required sites
• Make a detailed report on its features and your understanding of it

Results and Analysis

• Present the results of the study. You may consider visualising the results in tables and graphs, graphics etc.
• Analyse the results to obtain answer to the research question.
• Provide an analysis of the technical and financial feasibility, social acceptability etc

Discussion, Limitation(s) and Implication(s)

• Discuss your interpretations of the analysis and the significance of your findings
• Explain any new understanding or insights that emerged as a result of your research
• Consider the different perspectives (social, economic and environmental)in the discussion
• Explain the limitation(s)
• Explain how could what you found be used to make a difference for sustainability

Conclusion and Recommendations

• Summarise the significance and outcome of the study highlighting the key points.
• Come up with alternatives and propose specific actions based on the alternatives
• Describe the result or improvement it would achieve
• Explain how it will be implemented

Recommendations should have an innovative approach and should be feasible. It should make a significant difference in solving the issue under discussion.

• List the sources you have referred to in your writing
• Use the recommended citation style consistently in your report

Appendix (if necessary/any)

Include any material relating to the report and research that does not fit in the body of the report, in the appendix. For example, you may include survey questionnaire and results in the appendix.

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Organizing Your Social Sciences Research Assignments

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A case study research paper examines a person, place, event, condition, phenomenon, or other type of subject of analysis in order to extrapolate  key themes and results that help predict future trends, illuminate previously hidden issues that can be applied to practice, and/or provide a means for understanding an important research problem with greater clarity. A case study research paper usually examines a single subject of analysis, but case study papers can also be designed as a comparative investigation that shows relationships between two or more subjects. The methods used to study a case can rest within a quantitative, qualitative, or mixed-method investigative paradigm.

Case Studies. Writing@CSU. Colorado State University; Mills, Albert J. , Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010 ; “What is a Case Study?” In Swanborn, Peter G. Case Study Research: What, Why and How? London: SAGE, 2010.

How to Approach Writing a Case Study Research Paper

General information about how to choose a topic to investigate can be found under the " Choosing a Research Problem " tab in the Organizing Your Social Sciences Research Paper writing guide. Review this page because it may help you identify a subject of analysis that can be investigated using a case study design.

However, identifying a case to investigate involves more than choosing the research problem . A case study encompasses a problem contextualized around the application of in-depth analysis, interpretation, and discussion, often resulting in specific recommendations for action or for improving existing conditions. As Seawright and Gerring note, practical considerations such as time and access to information can influence case selection, but these issues should not be the sole factors used in describing the methodological justification for identifying a particular case to study. Given this, selecting a case includes considering the following:

• The case represents an unusual or atypical example of a research problem that requires more in-depth analysis? Cases often represent a topic that rests on the fringes of prior investigations because the case may provide new ways of understanding the research problem. For example, if the research problem is to identify strategies to improve policies that support girl's access to secondary education in predominantly Muslim nations, you could consider using Azerbaijan as a case study rather than selecting a more obvious nation in the Middle East. Doing so may reveal important new insights into recommending how governments in other predominantly Muslim nations can formulate policies that support improved access to education for girls.
• The case provides important insight or illuminate a previously hidden problem? In-depth analysis of a case can be based on the hypothesis that the case study will reveal trends or issues that have not been exposed in prior research or will reveal new and important implications for practice. For example, anecdotal evidence may suggest drug use among homeless veterans is related to their patterns of travel throughout the day. Assuming prior studies have not looked at individual travel choices as a way to study access to illicit drug use, a case study that observes a homeless veteran could reveal how issues of personal mobility choices facilitate regular access to illicit drugs. Note that it is important to conduct a thorough literature review to ensure that your assumption about the need to reveal new insights or previously hidden problems is valid and evidence-based.
• The case challenges and offers a counter-point to prevailing assumptions? Over time, research on any given topic can fall into a trap of developing assumptions based on outdated studies that are still applied to new or changing conditions or the idea that something should simply be accepted as "common sense," even though the issue has not been thoroughly tested in current practice. A case study analysis may offer an opportunity to gather evidence that challenges prevailing assumptions about a research problem and provide a new set of recommendations applied to practice that have not been tested previously. For example, perhaps there has been a long practice among scholars to apply a particular theory in explaining the relationship between two subjects of analysis. Your case could challenge this assumption by applying an innovative theoretical framework [perhaps borrowed from another discipline] to explore whether this approach offers new ways of understanding the research problem. Taking a contrarian stance is one of the most important ways that new knowledge and understanding develops from existing literature.
• The case provides an opportunity to pursue action leading to the resolution of a problem? Another way to think about choosing a case to study is to consider how the results from investigating a particular case may result in findings that reveal ways in which to resolve an existing or emerging problem. For example, studying the case of an unforeseen incident, such as a fatal accident at a railroad crossing, can reveal hidden issues that could be applied to preventative measures that contribute to reducing the chance of accidents in the future. In this example, a case study investigating the accident could lead to a better understanding of where to strategically locate additional signals at other railroad crossings so as to better warn drivers of an approaching train, particularly when visibility is hindered by heavy rain, fog, or at night.
• The case offers a new direction in future research? A case study can be used as a tool for an exploratory investigation that highlights the need for further research about the problem. A case can be used when there are few studies that help predict an outcome or that establish a clear understanding about how best to proceed in addressing a problem. For example, after conducting a thorough literature review [very important!], you discover that little research exists showing the ways in which women contribute to promoting water conservation in rural communities of east central Africa. A case study of how women contribute to saving water in a rural village of Uganda can lay the foundation for understanding the need for more thorough research that documents how women in their roles as cooks and family caregivers think about water as a valuable resource within their community. This example of a case study could also point to the need for scholars to build new theoretical frameworks around the topic [e.g., applying feminist theories of work and family to the issue of water conservation].

Eisenhardt, Kathleen M. “Building Theories from Case Study Research.” Academy of Management Review 14 (October 1989): 532-550; Emmel, Nick. Sampling and Choosing Cases in Qualitative Research: A Realist Approach . Thousand Oaks, CA: SAGE Publications, 2013; Gerring, John. “What Is a Case Study and What Is It Good for?” American Political Science Review 98 (May 2004): 341-354; Mills, Albert J. , Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010; Seawright, Jason and John Gerring. "Case Selection Techniques in Case Study Research." Political Research Quarterly 61 (June 2008): 294-308.

Structure and Writing Style

The purpose of a paper in the social sciences designed around a case study is to thoroughly investigate a subject of analysis in order to reveal a new understanding about the research problem and, in so doing, contributing new knowledge to what is already known from previous studies. In applied social sciences disciplines [e.g., education, social work, public administration, etc.], case studies may also be used to reveal best practices, highlight key programs, or investigate interesting aspects of professional work.

In general, the structure of a case study research paper is not all that different from a standard college-level research paper. However, there are subtle differences you should be aware of. Here are the key elements to organizing and writing a case study research paper.

I.  Introduction

As with any research paper, your introduction should serve as a roadmap for your readers to ascertain the scope and purpose of your study . The introduction to a case study research paper, however, should not only describe the research problem and its significance, but you should also succinctly describe why the case is being used and how it relates to addressing the problem. The two elements should be linked. With this in mind, a good introduction answers these four questions:

• What is being studied? Describe the research problem and describe the subject of analysis [the case] you have chosen to address the problem. Explain how they are linked and what elements of the case will help to expand knowledge and understanding about the problem.
• Why is this topic important to investigate? Describe the significance of the research problem and state why a case study design and the subject of analysis that the paper is designed around is appropriate in addressing the problem.
• What did we know about this topic before I did this study? Provide background that helps lead the reader into the more in-depth literature review to follow. If applicable, summarize prior case study research applied to the research problem and why it fails to adequately address the problem. Describe why your case will be useful. If no prior case studies have been used to address the research problem, explain why you have selected this subject of analysis.
• How will this study advance new knowledge or new ways of understanding? Explain why your case study will be suitable in helping to expand knowledge and understanding about the research problem.

Each of these questions should be addressed in no more than a few paragraphs. Exceptions to this can be when you are addressing a complex research problem or subject of analysis that requires more in-depth background information.

II.  Literature Review

The literature review for a case study research paper is generally structured the same as it is for any college-level research paper. The difference, however, is that the literature review is focused on providing background information and  enabling historical interpretation of the subject of analysis in relation to the research problem the case is intended to address . This includes synthesizing studies that help to:

• Place relevant works in the context of their contribution to understanding the case study being investigated . This would involve summarizing studies that have used a similar subject of analysis to investigate the research problem. If there is literature using the same or a very similar case to study, you need to explain why duplicating past research is important [e.g., conditions have changed; prior studies were conducted long ago, etc.].
• Describe the relationship each work has to the others under consideration that informs the reader why this case is applicable . Your literature review should include a description of any works that support using the case to investigate the research problem and the underlying research questions.
• Identify new ways to interpret prior research using the case study . If applicable, review any research that has examined the research problem using a different research design. Explain how your use of a case study design may reveal new knowledge or a new perspective or that can redirect research in an important new direction.
• Resolve conflicts amongst seemingly contradictory previous studies . This refers to synthesizing any literature that points to unresolved issues of concern about the research problem and describing how the subject of analysis that forms the case study can help resolve these existing contradictions.
• Point the way in fulfilling a need for additional research . Your review should examine any literature that lays a foundation for understanding why your case study design and the subject of analysis around which you have designed your study may reveal a new way of approaching the research problem or offer a perspective that points to the need for additional research.
• Expose any gaps that exist in the literature that the case study could help to fill . Summarize any literature that not only shows how your subject of analysis contributes to understanding the research problem, but how your case contributes to a new way of understanding the problem that prior research has failed to do.
• Locate your own research within the context of existing literature [very important!] . Collectively, your literature review should always place your case study within the larger domain of prior research about the problem. The overarching purpose of reviewing pertinent literature in a case study paper is to demonstrate that you have thoroughly identified and synthesized prior studies in relation to explaining the relevance of the case in addressing the research problem.

III.  Method

In this section, you explain why you selected a particular case [i.e., subject of analysis] and the strategy you used to identify and ultimately decide that your case was appropriate in addressing the research problem. The way you describe the methods used varies depending on the type of subject of analysis that constitutes your case study.

If your subject of analysis is an incident or event . In the social and behavioral sciences, the event or incident that represents the case to be studied is usually bounded by time and place, with a clear beginning and end and with an identifiable location or position relative to its surroundings. The subject of analysis can be a rare or critical event or it can focus on a typical or regular event. The purpose of studying a rare event is to illuminate new ways of thinking about the broader research problem or to test a hypothesis. Critical incident case studies must describe the method by which you identified the event and explain the process by which you determined the validity of this case to inform broader perspectives about the research problem or to reveal new findings. However, the event does not have to be a rare or uniquely significant to support new thinking about the research problem or to challenge an existing hypothesis. For example, Walo, Bull, and Breen conducted a case study to identify and evaluate the direct and indirect economic benefits and costs of a local sports event in the City of Lismore, New South Wales, Australia. The purpose of their study was to provide new insights from measuring the impact of a typical local sports event that prior studies could not measure well because they focused on large "mega-events." Whether the event is rare or not, the methods section should include an explanation of the following characteristics of the event: a) when did it take place; b) what were the underlying circumstances leading to the event; and, c) what were the consequences of the event in relation to the research problem.

If your subject of analysis is a person. Explain why you selected this particular individual to be studied and describe what experiences they have had that provide an opportunity to advance new understandings about the research problem. Mention any background about this person which might help the reader understand the significance of their experiences that make them worthy of study. This includes describing the relationships this person has had with other people, institutions, and/or events that support using them as the subject for a case study research paper. It is particularly important to differentiate the person as the subject of analysis from others and to succinctly explain how the person relates to examining the research problem [e.g., why is one politician in a particular local election used to show an increase in voter turnout from any other candidate running in the election]. Note that these issues apply to a specific group of people used as a case study unit of analysis [e.g., a classroom of students].

If your subject of analysis is a place. In general, a case study that investigates a place suggests a subject of analysis that is unique or special in some way and that this uniqueness can be used to build new understanding or knowledge about the research problem. A case study of a place must not only describe its various attributes relevant to the research problem [e.g., physical, social, historical, cultural, economic, political], but you must state the method by which you determined that this place will illuminate new understandings about the research problem. It is also important to articulate why a particular place as the case for study is being used if similar places also exist [i.e., if you are studying patterns of homeless encampments of veterans in open spaces, explain why you are studying Echo Park in Los Angeles rather than Griffith Park?]. If applicable, describe what type of human activity involving this place makes it a good choice to study [e.g., prior research suggests Echo Park has more homeless veterans].

If your subject of analysis is a phenomenon. A phenomenon refers to a fact, occurrence, or circumstance that can be studied or observed but with the cause or explanation to be in question. In this sense, a phenomenon that forms your subject of analysis can encompass anything that can be observed or presumed to exist but is not fully understood. In the social and behavioral sciences, the case usually focuses on human interaction within a complex physical, social, economic, cultural, or political system. For example, the phenomenon could be the observation that many vehicles used by ISIS fighters are small trucks with English language advertisements on them. The research problem could be that ISIS fighters are difficult to combat because they are highly mobile. The research questions could be how and by what means are these vehicles used by ISIS being supplied to the militants and how might supply lines to these vehicles be cut off? How might knowing the suppliers of these trucks reveal larger networks of collaborators and financial support? A case study of a phenomenon most often encompasses an in-depth analysis of a cause and effect that is grounded in an interactive relationship between people and their environment in some way.

NOTE:   The choice of the case or set of cases to study cannot appear random. Evidence that supports the method by which you identified and chose your subject of analysis should clearly support investigation of the research problem and linked to key findings from your literature review. Be sure to cite any studies that helped you determine that the case you chose was appropriate for examining the problem.

IV.  Discussion

The main elements of your discussion section are generally the same as any research paper, but centered around interpreting and drawing conclusions about the key findings from your analysis of the case study. Note that a general social sciences research paper may contain a separate section to report findings. However, in a paper designed around a case study, it is common to combine a description of the results with the discussion about their implications. The objectives of your discussion section should include the following:

Reiterate the Research Problem/State the Major Findings Briefly reiterate the research problem you are investigating and explain why the subject of analysis around which you designed the case study were used. You should then describe the findings revealed from your study of the case using direct, declarative, and succinct proclamation of the study results. Highlight any findings that were unexpected or especially profound.

Explain the Meaning of the Findings and Why They are Important Systematically explain the meaning of your case study findings and why you believe they are important. Begin this part of the section by repeating what you consider to be your most important or surprising finding first, then systematically review each finding. Be sure to thoroughly extrapolate what your analysis of the case can tell the reader about situations or conditions beyond the actual case that was studied while, at the same time, being careful not to misconstrue or conflate a finding that undermines the external validity of your conclusions.

Relate the Findings to Similar Studies No study in the social sciences is so novel or possesses such a restricted focus that it has absolutely no relation to previously published research. The discussion section should relate your case study results to those found in other studies, particularly if questions raised from prior studies served as the motivation for choosing your subject of analysis. This is important because comparing and contrasting the findings of other studies helps support the overall importance of your results and it highlights how and in what ways your case study design and the subject of analysis differs from prior research about the topic.

Consider Alternative Explanations of the Findings Remember that the purpose of social science research is to discover and not to prove. When writing the discussion section, you should carefully consider all possible explanations revealed by the case study results, rather than just those that fit your hypothesis or prior assumptions and biases. Be alert to what the in-depth analysis of the case may reveal about the research problem, including offering a contrarian perspective to what scholars have stated in prior research if that is how the findings can be interpreted from your case.

Acknowledge the Study's Limitations You can state the study's limitations in the conclusion section of your paper but describing the limitations of your subject of analysis in the discussion section provides an opportunity to identify the limitations and explain why they are not significant. This part of the discussion section should also note any unanswered questions or issues your case study could not address. More detailed information about how to document any limitations to your research can be found here .

Suggest Areas for Further Research Although your case study may offer important insights about the research problem, there are likely additional questions related to the problem that remain unanswered or findings that unexpectedly revealed themselves as a result of your in-depth analysis of the case. Be sure that the recommendations for further research are linked to the research problem and that you explain why your recommendations are valid in other contexts and based on the original assumptions of your study.

V.  Conclusion

As with any research paper, you should summarize your conclusion in clear, simple language; emphasize how the findings from your case study differs from or supports prior research and why. Do not simply reiterate the discussion section. Provide a synthesis of key findings presented in the paper to show how these converge to address the research problem. If you haven't already done so in the discussion section, be sure to document the limitations of your case study and any need for further research.

The function of your paper's conclusion is to: 1) reiterate the main argument supported by the findings from your case study; 2) state clearly the context, background, and necessity of pursuing the research problem using a case study design in relation to an issue, controversy, or a gap found from reviewing the literature; and, 3) provide a place to persuasively and succinctly restate the significance of your research problem, given that the reader has now been presented with in-depth information about the topic.

Consider the following points to help ensure your conclusion is appropriate:

• If the argument or purpose of your paper is complex, you may need to summarize these points for your reader.
• If prior to your conclusion, you have not yet explained the significance of your findings or if you are proceeding inductively, use the conclusion of your paper to describe your main points and explain their significance.
• Move from a detailed to a general level of consideration of the case study's findings that returns the topic to the context provided by the introduction or within a new context that emerges from your case study findings.

Note that, depending on the discipline you are writing in or the preferences of your professor, the concluding paragraph may contain your final reflections on the evidence presented as it applies to practice or on the essay's central research problem. However, the nature of being introspective about the subject of analysis you have investigated will depend on whether you are explicitly asked to express your observations in this way.

Problems to Avoid

Overgeneralization One of the goals of a case study is to lay a foundation for understanding broader trends and issues applied to similar circumstances. However, be careful when drawing conclusions from your case study. They must be evidence-based and grounded in the results of the study; otherwise, it is merely speculation. Looking at a prior example, it would be incorrect to state that a factor in improving girls access to education in Azerbaijan and the policy implications this may have for improving access in other Muslim nations is due to girls access to social media if there is no documentary evidence from your case study to indicate this. There may be anecdotal evidence that retention rates were better for girls who were engaged with social media, but this observation would only point to the need for further research and would not be a definitive finding if this was not a part of your original research agenda.

Failure to Document Limitations No case is going to reveal all that needs to be understood about a research problem. Therefore, just as you have to clearly state the limitations of a general research study , you must describe the specific limitations inherent in the subject of analysis. For example, the case of studying how women conceptualize the need for water conservation in a village in Uganda could have limited application in other cultural contexts or in areas where fresh water from rivers or lakes is plentiful and, therefore, conservation is understood more in terms of managing access rather than preserving access to a scarce resource.

Failure to Extrapolate All Possible Implications Just as you don't want to over-generalize from your case study findings, you also have to be thorough in the consideration of all possible outcomes or recommendations derived from your findings. If you do not, your reader may question the validity of your analysis, particularly if you failed to document an obvious outcome from your case study research. For example, in the case of studying the accident at the railroad crossing to evaluate where and what types of warning signals should be located, you failed to take into consideration speed limit signage as well as warning signals. When designing your case study, be sure you have thoroughly addressed all aspects of the problem and do not leave gaps in your analysis that leave the reader questioning the results.

Case Studies. Writing@CSU. Colorado State University; Gerring, John. Case Study Research: Principles and Practices . New York: Cambridge University Press, 2007; Merriam, Sharan B. Qualitative Research and Case Study Applications in Education . Rev. ed. San Francisco, CA: Jossey-Bass, 1998; Miller, Lisa L. “The Use of Case Studies in Law and Social Science Research.” Annual Review of Law and Social Science 14 (2018): TBD; Mills, Albert J., Gabrielle Durepos, and Eiden Wiebe, editors. Encyclopedia of Case Study Research . Thousand Oaks, CA: SAGE Publications, 2010; Putney, LeAnn Grogan. "Case Study." In Encyclopedia of Research Design , Neil J. Salkind, editor. (Thousand Oaks, CA: SAGE Publications, 2010), pp. 116-120; Simons, Helen. Case Study Research in Practice . London: SAGE Publications, 2009;  Kratochwill,  Thomas R. and Joel R. Levin, editors. Single-Case Research Design and Analysis: New Development for Psychology and Education .  Hilldsale, NJ: Lawrence Erlbaum Associates, 1992; Swanborn, Peter G. Case Study Research: What, Why and How? London : SAGE, 2010; Yin, Robert K. Case Study Research: Design and Methods . 6th edition. Los Angeles, CA, SAGE Publications, 2014; Walo, Maree, Adrian Bull, and Helen Breen. “Achieving Economic Benefits at Local Events: A Case Study of a Local Sports Event.” Festival Management and Event Tourism 4 (1996): 95-106.

Writing Tip

At Least Five Misconceptions about Case Study Research

Social science case studies are often perceived as limited in their ability to create new knowledge because they are not randomly selected and findings cannot be generalized to larger populations. Flyvbjerg examines five misunderstandings about case study research and systematically "corrects" each one. To quote, these are:

Misunderstanding 1 :  General, theoretical [context-independent] knowledge is more valuable than concrete, practical [context-dependent] knowledge. Misunderstanding 2 :  One cannot generalize on the basis of an individual case; therefore, the case study cannot contribute to scientific development. Misunderstanding 3 :  The case study is most useful for generating hypotheses; that is, in the first stage of a total research process, whereas other methods are more suitable for hypotheses testing and theory building. Misunderstanding 4 :  The case study contains a bias toward verification, that is, a tendency to confirm the researcher’s preconceived notions. Misunderstanding 5 :  It is often difficult to summarize and develop general propositions and theories on the basis of specific case studies [p. 221].

While writing your paper, think introspectively about how you addressed these misconceptions because to do so can help you strengthen the validity and reliability of your research by clarifying issues of case selection, the testing and challenging of existing assumptions, the interpretation of key findings, and the summation of case outcomes. Think of a case study research paper as a complete, in-depth narrative about the specific properties and key characteristics of your subject of analysis applied to the research problem.

Flyvbjerg, Bent. “Five Misunderstandings About Case-Study Research.” Qualitative Inquiry 12 (April 2006): 219-245.

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Methodology or method? A critical review of qualitative case study reports

Despite on-going debate about credibility, and reported limitations in comparison to other approaches, case study is an increasingly popular approach among qualitative researchers. We critically analysed the methodological descriptions of published case studies. Three high-impact qualitative methods journals were searched to locate case studies published in the past 5 years; 34 were selected for analysis. Articles were categorized as health and health services ( n= 12), social sciences and anthropology ( n= 7), or methods ( n= 15) case studies. The articles were reviewed using an adapted version of established criteria to determine whether adequate methodological justification was present, and if study aims, methods, and reported findings were consistent with a qualitative case study approach. Findings were grouped into five themes outlining key methodological issues: case study methodology or method, case of something particular and case selection, contextually bound case study, researcher and case interactions and triangulation, and study design inconsistent with methodology reported. Improved reporting of case studies by qualitative researchers will advance the methodology for the benefit of researchers and practitioners.

Case study research is an increasingly popular approach among qualitative researchers (Thomas, 2011 ). Several prominent authors have contributed to methodological developments, which has increased the popularity of case study approaches across disciplines (Creswell, 2013b ; Denzin & Lincoln, 2011b ; Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Current qualitative case study approaches are shaped by paradigm, study design, and selection of methods, and, as a result, case studies in the published literature vary. Differences between published case studies can make it difficult for researchers to define and understand case study as a methodology.

Experienced qualitative researchers have identified case study research as a stand-alone qualitative approach (Denzin & Lincoln, 2011b ). Case study research has a level of flexibility that is not readily offered by other qualitative approaches such as grounded theory or phenomenology. Case studies are designed to suit the case and research question and published case studies demonstrate wide diversity in study design. There are two popular case study approaches in qualitative research. The first, proposed by Stake ( 1995 ) and Merriam ( 2009 ), is situated in a social constructivist paradigm, whereas the second, by Yin ( 2012 ), Flyvbjerg ( 2011 ), and Eisenhardt ( 1989 ), approaches case study from a post-positivist viewpoint. Scholarship from both schools of inquiry has contributed to the popularity of case study and development of theoretical frameworks and principles that characterize the methodology.

The diversity of case studies reported in the published literature, and on-going debates about credibility and the use of case study in qualitative research practice, suggests that differences in perspectives on case study methodology may prevent researchers from developing a mutual understanding of practice and rigour. In addition, discussion about case study limitations has led some authors to query whether case study is indeed a methodology (Luck, Jackson, & Usher, 2006 ; Meyer, 2001 ; Thomas, 2010 ; Tight, 2010 ). Methodological discussion of qualitative case study research is timely, and a review is required to analyse and understand how this methodology is applied in the qualitative research literature. The aims of this study were to review methodological descriptions of published qualitative case studies, to review how the case study methodological approach was applied, and to identify issues that need to be addressed by researchers, editors, and reviewers. An outline of the current definitions of case study and an overview of the issues proposed in the qualitative methodological literature are provided to set the scene for the review.

Definitions of qualitative case study research

Case study research is an investigation and analysis of a single or collective case, intended to capture the complexity of the object of study (Stake, 1995 ). Qualitative case study research, as described by Stake ( 1995 ), draws together “naturalistic, holistic, ethnographic, phenomenological, and biographic research methods” in a bricoleur design, or in his words, “a palette of methods” (Stake, 1995 , pp. xi–xii). Case study methodology maintains deep connections to core values and intentions and is “particularistic, descriptive and heuristic” (Merriam, 2009 , p. 46).

As a study design, case study is defined by interest in individual cases rather than the methods of inquiry used. The selection of methods is informed by researcher and case intuition and makes use of naturally occurring sources of knowledge, such as people or observations of interactions that occur in the physical space (Stake, 1998 ). Thomas ( 2011 ) suggested that “analytical eclecticism” is a defining factor (p. 512). Multiple data collection and analysis methods are adopted to further develop and understand the case, shaped by context and emergent data (Stake, 1995 ). This qualitative approach “explores a real-life, contemporary bounded system (a case ) or multiple bounded systems (cases) over time, through detailed, in-depth data collection involving multiple sources of information … and reports a case description and case themes ” (Creswell, 2013b , p. 97). Case study research has been defined by the unit of analysis, the process of study, and the outcome or end product, all essentially the case (Merriam, 2009 ).

The case is an object to be studied for an identified reason that is peculiar or particular. Classification of the case and case selection procedures informs development of the study design and clarifies the research question. Stake ( 1995 ) proposed three types of cases and study design frameworks. These include the intrinsic case, the instrumental case, and the collective instrumental case. The intrinsic case is used to understand the particulars of a single case, rather than what it represents. An instrumental case study provides insight on an issue or is used to refine theory. The case is selected to advance understanding of the object of interest. A collective refers to an instrumental case which is studied as multiple, nested cases, observed in unison, parallel, or sequential order. More than one case can be simultaneously studied; however, each case study is a concentrated, single inquiry, studied holistically in its own entirety (Stake, 1995 , 1998 ).

Researchers who use case study are urged to seek out what is common and what is particular about the case. This involves careful and in-depth consideration of the nature of the case, historical background, physical setting, and other institutional and political contextual factors (Stake, 1998 ). An interpretive or social constructivist approach to qualitative case study research supports a transactional method of inquiry, where the researcher has a personal interaction with the case. The case is developed in a relationship between the researcher and informants, and presented to engage the reader, inviting them to join in this interaction and in case discovery (Stake, 1995 ). A postpositivist approach to case study involves developing a clear case study protocol with careful consideration of validity and potential bias, which might involve an exploratory or pilot phase, and ensures that all elements of the case are measured and adequately described (Yin, 2009 , 2012 ).

Current methodological issues in qualitative case study research

The future of qualitative research will be influenced and constructed by the way research is conducted, and by what is reviewed and published in academic journals (Morse, 2011 ). If case study research is to further develop as a principal qualitative methodological approach, and make a valued contribution to the field of qualitative inquiry, issues related to methodological credibility must be considered. Researchers are required to demonstrate rigour through adequate descriptions of methodological foundations. Case studies published without sufficient detail for the reader to understand the study design, and without rationale for key methodological decisions, may lead to research being interpreted as lacking in quality or credibility (Hallberg, 2013 ; Morse, 2011 ).

There is a level of artistic license that is embraced by qualitative researchers and distinguishes practice, which nurtures creativity, innovation, and reflexivity (Denzin & Lincoln, 2011b ; Morse, 2009 ). Qualitative research is “inherently multimethod” (Denzin & Lincoln, 2011a , p. 5); however, with this creative freedom, it is important for researchers to provide adequate description for methodological justification (Meyer, 2001 ). This includes paradigm and theoretical perspectives that have influenced study design. Without adequate description, study design might not be understood by the reader, and can appear to be dishonest or inaccurate. Reviewers and readers might be confused by the inconsistent or inappropriate terms used to describe case study research approach and methods, and be distracted from important study findings (Sandelowski, 2000 ). This issue extends beyond case study research, and others have noted inconsistencies in reporting of methodology and method by qualitative researchers. Sandelowski ( 2000 , 2010 ) argued for accurate identification of qualitative description as a research approach. She recommended that the selected methodology should be harmonious with the study design, and be reflected in methods and analysis techniques. Similarly, Webb and Kevern ( 2000 ) uncovered inconsistencies in qualitative nursing research with focus group methods, recommending that methodological procedures must cite seminal authors and be applied with respect to the selected theoretical framework. Incorrect labelling using case study might stem from the flexibility in case study design and non-directional character relative to other approaches (Rosenberg & Yates, 2007 ). Methodological integrity is required in design of qualitative studies, including case study, to ensure study rigour and to enhance credibility of the field (Morse, 2011 ).

Case study has been unnecessarily devalued by comparisons with statistical methods (Eisenhardt, 1989 ; Flyvbjerg, 2006 , 2011 ; Jensen & Rodgers, 2001 ; Piekkari, Welch, & Paavilainen, 2009 ; Tight, 2010 ; Yin, 1999 ). It is reputed to be the “the weak sibling” in comparison to other, more rigorous, approaches (Yin, 2009 , p. xiii). Case study is not an inherently comparative approach to research. The objective is not statistical research, and the aim is not to produce outcomes that are generalizable to all populations (Thomas, 2011 ). Comparisons between case study and statistical research do little to advance this qualitative approach, and fail to recognize its inherent value, which can be better understood from the interpretive or social constructionist viewpoint of other authors (Merriam, 2009 ; Stake, 1995 ). Building on discussions relating to “fuzzy” (Bassey, 2001 ), or naturalistic generalizations (Stake, 1978 ), or transference of concepts and theories (Ayres, Kavanaugh, & Knafl, 2003 ; Morse et al., 2011 ) would have more relevance.

Case study research has been used as a catch-all design to justify or add weight to fundamental qualitative descriptive studies that do not fit with other traditional frameworks (Merriam, 2009 ). A case study has been a “convenient label for our research—when we ‘can't think of anything ‘better”—in an attempt to give it [qualitative methodology] some added respectability” (Tight, 2010 , p. 337). Qualitative case study research is a pliable approach (Merriam, 2009 ; Meyer, 2001 ; Stake, 1995 ), and has been likened to a “curious methodological limbo” (Gerring, 2004 , p. 341) or “paradigmatic bridge” (Luck et al., 2006 , p. 104), that is on the borderline between postpositivist and constructionist interpretations. This has resulted in inconsistency in application, which indicates that flexibility comes with limitations (Meyer, 2001 ), and the open nature of case study research might be off-putting to novice researchers (Thomas, 2011 ). The development of a well-(in)formed theoretical framework to guide a case study should improve consistency, rigour, and trust in studies published in qualitative research journals (Meyer, 2001 ).

Assessment of rigour

The purpose of this study was to analyse the methodological descriptions of case studies published in qualitative methods journals. To do this we needed to develop a suitable framework, which used existing, established criteria for appraising qualitative case study research rigour (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ). A number of qualitative authors have developed concepts and criteria that are used to determine whether a study is rigorous (Denzin & Lincoln, 2011b ; Lincoln, 1995 ; Sandelowski & Barroso, 2002 ). The criteria proposed by Stake ( 1995 ) provide a framework for readers and reviewers to make judgements regarding case study quality, and identify key characteristics essential for good methodological rigour. Although each of the factors listed in Stake's criteria could enhance the quality of a qualitative research report, in Table I we present an adapted criteria used in this study, which integrates more recent work by Merriam ( 2009 ) and Creswell ( 2013b ). Stake's ( 1995 ) original criteria were separated into two categories. The first list of general criteria is “relevant for all qualitative research.” The second list, “high relevance to qualitative case study research,” was the criteria that we decided had higher relevance to case study research. This second list was the main criteria used to assess the methodological descriptions of the case studies reviewed. The complete table has been preserved so that the reader can determine how the original criteria were adapted.

Framework for assessing quality in qualitative case study research.

Adapted from Stake ( 1995 , p. 131).

Study design

The critical review method described by Grant and Booth ( 2009 ) was used, which is appropriate for the assessment of research quality, and is used for literature analysis to inform research and practice. This type of review goes beyond the mapping and description of scoping or rapid reviews, to include “analysis and conceptual innovation” (Grant & Booth, 2009 , p. 93). A critical review is used to develop existing, or produce new, hypotheses or models. This is different to systematic reviews that answer clinical questions. It is used to evaluate existing research and competing ideas, to provide a “launch pad” for conceptual development and “subsequent testing” (Grant & Booth, 2009 , p. 93).

Qualitative methods journals were located by a search of the 2011 ISI Journal Citation Reports in Social Science, via the database Web of Knowledge (see m.webofknowledge.com). No “qualitative research methods” category existed in the citation reports; therefore, a search of all categories was performed using the term “qualitative.” In Table II , we present the qualitative methods journals located, ranked by impact factor. The highest ranked journals were selected for searching. We acknowledge that the impact factor ranking system might not be the best measure of journal quality (Cheek, Garnham, & Quan, 2006 ); however, this was the most appropriate and accessible method available.

International Journal of Qualitative Studies on Health and Well-being.

Search strategy

In March 2013, searches of the journals, Qualitative Health Research , Qualitative Research , and Qualitative Inquiry were completed to retrieve studies with “case study” in the abstract field. The search was limited to the past 5 years (1 January 2008 to 1 March 2013). The objective was to locate published qualitative case studies suitable for assessment using the adapted criterion. Viewpoints, commentaries, and other article types were excluded from review. Title and abstracts of the 45 retrieved articles were read by the first author, who identified 34 empirical case studies for review. All authors reviewed the 34 studies to confirm selection and categorization. In Table III , we present the 34 case studies grouped by journal, and categorized by research topic, including health sciences, social sciences and anthropology, and methods research. There was a discrepancy in categorization of one article on pedagogy and a new teaching method published in Qualitative Inquiry (Jorrín-Abellán, Rubia-Avi, Anguita-Martínez, Gómez-Sánchez, & Martínez-Mones, 2008 ). Consensus was to allocate to the methods category.

Outcomes of search of qualitative methods journals.

In Table III , the number of studies located, and final numbers selected for review have been reported. Qualitative Health Research published the most empirical case studies ( n= 16). In the health category, there were 12 case studies of health conditions, health services, and health policy issues, all published in Qualitative Health Research . Seven case studies were categorized as social sciences and anthropology research, which combined case study with biography and ethnography methodologies. All three journals published case studies on methods research to illustrate a data collection or analysis technique, methodological procedure, or related issue.

The methodological descriptions of 34 case studies were critically reviewed using the adapted criteria. All articles reviewed contained a description of study methods; however, the length, amount of detail, and position of the description in the article varied. Few studies provided an accurate description and rationale for using a qualitative case study approach. In the 34 case studies reviewed, three described a theoretical framework informed by Stake ( 1995 ), two by Yin ( 2009 ), and three provided a mixed framework informed by various authors, which might have included both Yin and Stake. Few studies described their case study design, or included a rationale that explained why they excluded or added further procedures, and whether this was to enhance the study design, or to better suit the research question. In 26 of the studies no reference was provided to principal case study authors. From reviewing the description of methods, few authors provided a description or justification of case study methodology that demonstrated how their study was informed by the methodological literature that exists on this approach.

The methodological descriptions of each study were reviewed using the adapted criteria, and the following issues were identified: case study methodology or method; case of something particular and case selection; contextually bound case study; researcher and case interactions and triangulation; and, study design inconsistent with methodology. An outline of how the issues were developed from the critical review is provided, followed by a discussion of how these relate to the current methodological literature.

Case study methodology or method

A third of the case studies reviewed appeared to use a case report method, not case study methodology as described by principal authors (Creswell, 2013b ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). Case studies were identified as a case report because of missing methodological detail and by review of the study aims and purpose. These reports presented data for small samples of no more than three people, places or phenomenon. Four studies, or “case reports” were single cases selected retrospectively from larger studies (Bronken, Kirkevold, Martinsen, & Kvigne, 2012 ; Coltart & Henwood, 2012 ; Hooghe, Neimeyer, & Rober, 2012 ; Roscigno et al., 2012 ). Case reports were not a case of something, instead were a case demonstration or an example presented in a report. These reports presented outcomes, and reported on how the case could be generalized. Descriptions focussed on the phenomena, rather than the case itself, and did not appear to study the case in its entirety.

Case reports had minimal in-text references to case study methodology, and were informed by other qualitative traditions or secondary sources (Adamson & Holloway, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nagar-Ron & Motzafi-Haller, 2011 ). This does not suggest that case study methodology cannot be multimethod, however, methodology should be consistent in design, be clearly described (Meyer, 2001 ; Stake, 1995 ), and maintain focus on the case (Creswell, 2013b ).

To demonstrate how case reports were identified, three examples are provided. The first, Yeh ( 2013 ) described their study as, “the examination of the emergence of vegetarianism in Victorian England serves as a case study to reveal the relationships between boundaries and entities” (p. 306). The findings were a historical case report, which resulted from an ethnographic study of vegetarianism. Cunsolo Willox, Harper, Edge, ‘My Word’: Storytelling and Digital Media Lab, and Rigolet Inuit Community Government (2013) used “a case study that illustrates the usage of digital storytelling within an Inuit community” (p. 130). This case study reported how digital storytelling can be used with indigenous communities as a participatory method to illuminate the benefits of this method for other studies. This “case study was conducted in the Inuit community” but did not include the Inuit community in case analysis (Cunsolo Willox et al., 2013 , p. 130). Bronken et al. ( 2012 ) provided a single case report to demonstrate issues observed in a larger clinical study of aphasia and stroke, without adequate case description or analysis.

Case study of something particular and case selection

Case selection is a precursor to case analysis, which needs to be presented as a convincing argument (Merriam, 2009 ). Descriptions of the case were often not adequate to ascertain why the case was selected, or whether it was a particular exemplar or outlier (Thomas, 2011 ). In a number of case studies in the health and social science categories, it was not explicit whether the case was of something particular, or peculiar to their discipline or field (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson, Botelho, Welch, Joseph, & Tennstedt, 2012 ; Mawn et al., 2010 ; Snyder-Young, 2011 ). There were exceptions in the methods category ( Table III ), where cases were selected by researchers to report on a new or innovative method. The cases emerged through heuristic study, and were reported to be particular, relative to the existing methods literature (Ajodhia-Andrews & Berman, 2009 ; Buckley & Waring, 2013 ; Cunsolo Willox et al., 2013 ; De Haene, Grietens, & Verschueren, 2010 ; Gratton & O'Donnell, 2011 ; Sumsion, 2013 ; Wimpenny & Savin-Baden, 2012 ).

Case selection processes were sometimes insufficient to understand why the case was selected from the global population of cases, or what study of this case would contribute to knowledge as compared with other possible cases (Adamson & Holloway, 2012 ; Bronken et al., 2012 ; Colón-Emeric et al., 2010 ; Jackson et al., 2012 ; Mawn et al., 2010 ). In two studies, local cases were selected (Barone, 2010 ; Fourie & Theron, 2012 ) because the researcher was familiar with and had access to the case. Possible limitations of a convenience sample were not acknowledged. Purposeful sampling was used to recruit participants within the case of one study, but not of the case itself (Gallagher et al., 2013 ). Random sampling was completed for case selection in two studies (Colón-Emeric et al., 2010 ; Jackson et al., 2012 ), which has limited meaning in interpretive qualitative research.

To demonstrate how researchers provided a good justification for the selection of case study approaches, four examples are provided. The first, cases of residential care homes, were selected because of reported occurrences of mistreatment, which included residents being locked in rooms at night (Rytterström, Unosson, & Arman, 2013 ). Roscigno et al. ( 2012 ) selected cases of parents who were admitted for early hospitalization in neonatal intensive care with a threatened preterm delivery before 26 weeks. Hooghe et al. ( 2012 ) used random sampling to select 20 couples that had experienced the death of a child; however, the case study was of one couple and a particular metaphor described only by them. The final example, Coltart and Henwood ( 2012 ), provided a detailed account of how they selected two cases from a sample of 46 fathers based on personal characteristics and beliefs. They described how the analysis of the two cases would contribute to their larger study on first time fathers and parenting.

Contextually bound case study

The limits or boundaries of the case are a defining factor of case study methodology (Merriam, 2009 ; Ragin & Becker, 1992 ; Stake, 1995 ; Yin, 2009 ). Adequate contextual description is required to understand the setting or context in which the case is revealed. In the health category, case studies were used to illustrate a clinical phenomenon or issue such as compliance and health behaviour (Colón-Emeric et al., 2010 ; D'Enbeau, Buzzanell, & Duckworth, 2010 ; Gallagher et al., 2013 ; Hooghe et al., 2012 ; Jackson et al., 2012 ; Roscigno et al., 2012 ). In these case studies, contextual boundaries, such as physical and institutional descriptions, were not sufficient to understand the case as a holistic system, for example, the general practitioner (GP) clinic in Gallagher et al. ( 2013 ), or the nursing home in Colón-Emeric et al. ( 2010 ). Similarly, in the social science and methods categories, attention was paid to some components of the case context, but not others, missing important information required to understand the case as a holistic system (Alexander, Moreira, & Kumar, 2012 ; Buzzanell & D'Enbeau, 2009 ; Nairn & Panelli, 2009 ; Wimpenny & Savin-Baden, 2012 ).

In two studies, vicarious experience or vignettes (Nairn & Panelli, 2009 ) and images (Jorrín-Abellán et al., 2008 ) were effective to support description of context, and might have been a useful addition for other case studies. Missing contextual boundaries suggests that the case might not be adequately defined. Additional information, such as the physical, institutional, political, and community context, would improve understanding of the case (Stake, 1998 ). In Boxes 1 and 2 , we present brief synopses of two studies that were reviewed, which demonstrated a well bounded case. In Box 1 , Ledderer ( 2011 ) used a qualitative case study design informed by Stake's tradition. In Box 2 , Gillard, Witt, and Watts ( 2011 ) were informed by Yin's tradition. By providing a brief outline of the case studies in Boxes 1 and 2 , we demonstrate how effective case boundaries can be constructed and reported, which may be of particular interest to prospective case study researchers.

Article synopsis of case study research using Stake's tradition

Ledderer ( 2011 ) used a qualitative case study research design, informed by modern ethnography. The study is bounded to 10 general practice clinics in Denmark, who had received federal funding to implement preventative care services based on a Motivational Interviewing intervention. The researcher question focussed on “why is it so difficult to create change in medical practice?” (Ledderer, 2011 , p. 27). The study context was adequately described, providing detail on the general practitioner (GP) clinics and relevant political and economic influences. Methodological decisions are described in first person narrative, providing insight on researcher perspectives and interaction with the case. Forty-four interviews were conducted, which focussed on how GPs conducted consultations, and the form, nature and content, rather than asking their opinion or experience (Ledderer, 2011 , p. 30). The duration and intensity of researcher immersion in the case enhanced depth of description and trustworthiness of study findings. Analysis was consistent with Stake's tradition, and the researcher provided examples of inquiry techniques used to challenge assumptions about emerging themes. Several other seminal qualitative works were cited. The themes and typology constructed are rich in narrative data and storytelling by clinic staff, demonstrating individual clinic experiences as well as shared meanings and understandings about changing from a biomedical to psychological approach to preventative health intervention. Conclusions make note of social and cultural meanings and lessons learned, which might not have been uncovered using a different methodology.

Article synopsis of case study research using Yin's tradition

Gillard et al. ( 2011 ) study of camps for adolescents living with HIV/AIDs provided a good example of Yin's interpretive case study approach. The context of the case is bounded by the three summer camps of which the researchers had prior professional involvement. A case study protocol was developed that used multiple methods to gather information at three data collection points coinciding with three youth camps (Teen Forum, Discover Camp, and Camp Strong). Gillard and colleagues followed Yin's ( 2009 ) principles, using a consistent data protocol that enhanced cross-case analysis. Data described the young people, the camp physical environment, camp schedule, objectives and outcomes, and the staff of three youth camps. The findings provided a detailed description of the context, with less detail of individual participants, including insight into researcher's interpretations and methodological decisions throughout the data collection and analysis process. Findings provided the reader with a sense of “being there,” and are discovered through constant comparison of the case with the research issues; the case is the unit of analysis. There is evidence of researcher immersion in the case, and Gillard reports spending significant time in the field in a naturalistic and integrated youth mentor role.

This case study is not intended to have a significant impact on broader health policy, although does have implications for health professionals working with adolescents. Study conclusions will inform future camps for young people with chronic disease, and practitioners are able to compare similarities between this case and their own practice (for knowledge translation). No limitations of this article were reported. Limitations related to publication of this case study were that it was 20 pages long and used three tables to provide sufficient description of the camp and program components, and relationships with the research issue.

Researcher and case interactions and triangulation

Researcher and case interactions and transactions are a defining feature of case study methodology (Stake, 1995 ). Narrative stories, vignettes, and thick description are used to provoke vicarious experience and a sense of being there with the researcher in their interaction with the case. Few of the case studies reviewed provided details of the researcher's relationship with the case, researcher–case interactions, and how these influenced the development of the case study (Buzzanell & D'Enbeau, 2009 ; D'Enbeau et al., 2010 ; Gallagher et al., 2013 ; Gillard et al., 2011 ; Ledderer, 2011 ; Nagar-Ron & Motzafi-Haller, 2011 ). The role and position of the researcher needed to be self-examined and understood by readers, to understand how this influenced interactions with participants, and to determine what triangulation is needed (Merriam, 2009 ; Stake, 1995 ).

Gillard et al. ( 2011 ) provided a good example of triangulation, comparing data sources in a table (p. 1513). Triangulation of sources was used to reveal as much depth as possible in the study by Nagar-Ron and Motzafi-Haller ( 2011 ), while also enhancing confirmation validity. There were several case studies that would have benefited from improved range and use of data sources, and descriptions of researcher–case interactions (Ajodhia-Andrews & Berman, 2009 ; Bronken et al., 2012 ; Fincham, Scourfield, & Langer, 2008 ; Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Snyder-Young, 2011 ; Yeh, 2013 ).

Study design inconsistent with methodology

Good, rigorous case studies require a strong methodological justification (Meyer, 2001 ) and a logical and coherent argument that defines paradigm, methodological position, and selection of study methods (Denzin & Lincoln, 2011b ). Methodological justification was insufficient in several of the studies reviewed (Barone, 2010 ; Bronken et al., 2012 ; Hooghe et al., 2012 ; Mawn et al., 2010 ; Roscigno et al., 2012 ; Yeh, 2013 ). This was judged by the absence, or inadequate or inconsistent reference to case study methodology in-text.

In six studies, the methodological justification provided did not relate to case study. There were common issues identified. Secondary sources were used as primary methodological references indicating that study design might not have been theoretically sound (Colón-Emeric et al., 2010 ; Coltart & Henwood, 2012 ; Roscigno et al., 2012 ; Snyder-Young, 2011 ). Authors and sources cited in methodological descriptions were inconsistent with the actual study design and practices used (Fourie & Theron, 2012 ; Hooghe et al., 2012 ; Jorrín-Abellán et al., 2008 ; Mawn et al., 2010 ; Rytterström et al., 2013 ; Wimpenny & Savin-Baden, 2012 ). This occurred when researchers cited Stake or Yin, or both (Mawn et al., 2010 ; Rytterström et al., 2013 ), although did not follow their paradigmatic or methodological approach. In 26 studies there were no citations for a case study methodological approach.

The findings of this study have highlighted a number of issues for researchers. A considerable number of case studies reviewed were missing key elements that define qualitative case study methodology and the tradition cited. A significant number of studies did not provide a clear methodological description or justification relevant to case study. Case studies in health and social sciences did not provide sufficient information for the reader to understand case selection, and why this case was chosen above others. The context of the cases were not described in adequate detail to understand all relevant elements of the case context, which indicated that cases may have not been contextually bounded. There were inconsistencies between reported methodology, study design, and paradigmatic approach in case studies reviewed, which made it difficult to understand the study methodology and theoretical foundations. These issues have implications for methodological integrity and honesty when reporting study design, which are values of the qualitative research tradition and are ethical requirements (Wager & Kleinert, 2010a ). Poorly described methodological descriptions may lead the reader to misinterpret or discredit study findings, which limits the impact of the study, and, as a collective, hinders advancements in the broader qualitative research field.

The issues highlighted in our review build on current debates in the case study literature, and queries about the value of this methodology. Case study research can be situated within different paradigms or designed with an array of methods. In order to maintain the creativity and flexibility that is valued in this methodology, clearer descriptions of paradigm and theoretical position and methods should be provided so that study findings are not undervalued or discredited. Case study research is an interdisciplinary practice, which means that clear methodological descriptions might be more important for this approach than other methodologies that are predominantly driven by fewer disciplines (Creswell, 2013b ).

Authors frequently omit elements of methodologies and include others to strengthen study design, and we do not propose a rigid or purist ideology in this paper. On the contrary, we encourage new ideas about using case study, together with adequate reporting, which will advance the value and practice of case study. The implications of unclear methodological descriptions in the studies reviewed were that study design appeared to be inconsistent with reported methodology, and key elements required for making judgements of rigour were missing. It was not clear whether the deviations from methodological tradition were made by researchers to strengthen the study design, or because of misinterpretations. Morse ( 2011 ) recommended that innovations and deviations from practice are best made by experienced researchers, and that a novice might be unaware of the issues involved with making these changes. To perpetuate the tradition of case study research, applications in the published literature should have consistencies with traditional methodological constructions, and deviations should be described with a rationale that is inherent in study conduct and findings. Providing methodological descriptions that demonstrate a strong theoretical foundation and coherent study design will add credibility to the study, while ensuring the intrinsic meaning of case study is maintained.

The value of this review is that it contributes to discussion of whether case study is a methodology or method. We propose possible reasons why researchers might make this misinterpretation. Researchers may interchange the terms methods and methodology, and conduct research without adequate attention to epistemology and historical tradition (Carter & Little, 2007 ; Sandelowski, 2010 ). If the rich meaning that naming a qualitative methodology brings to the study is not recognized, a case study might appear to be inconsistent with the traditional approaches described by principal authors (Creswell, 2013a ; Merriam, 2009 ; Stake, 1995 ; Yin, 2009 ). If case studies are not methodologically and theoretically situated, then they might appear to be a case report.

Case reports are promoted by university and medical journals as a method of reporting on medical or scientific cases; guidelines for case reports are publicly available on websites ( http://www.hopkinsmedicine.org/institutional_review_board/guidelines_policies/guidelines/case_report.html ). The various case report guidelines provide a general criteria for case reports, which describes that this form of report does not meet the criteria of research, is used for retrospective analysis of up to three clinical cases, and is primarily illustrative and for educational purposes. Case reports can be published in academic journals, but do not require approval from a human research ethics committee. Traditionally, case reports describe a single case, to explain how and what occurred in a selected setting, for example, to illustrate a new phenomenon that has emerged from a larger study. A case report is not necessarily particular or the study of a case in its entirety, and the larger study would usually be guided by a different research methodology.

This description of a case report is similar to what was provided in some studies reviewed. This form of report lacks methodological grounding and qualities of research rigour. The case report has publication value in demonstrating an example and for dissemination of knowledge (Flanagan, 1999 ). However, case reports have different meaning and purpose to case study, which needs to be distinguished. Findings of our review suggest that the medical understanding of a case report has been confused with qualitative case study approaches.

In this review, a number of case studies did not have methodological descriptions that included key characteristics of case study listed in the adapted criteria, and several issues have been discussed. There have been calls for improvements in publication quality of qualitative research (Morse, 2011 ), and for improvements in peer review of submitted manuscripts (Carter & Little, 2007 ; Jasper, Vaismoradi, Bondas, & Turunen, 2013 ). The challenging nature of editor and reviewers responsibilities are acknowledged in the literature (Hames, 2013 ; Wager & Kleinert, 2010b ); however, review of case study methodology should be prioritized because of disputes on methodological value.

Authors using case study approaches are recommended to describe their theoretical framework and methods clearly, and to seek and follow specialist methodological advice when needed (Wager & Kleinert, 2010a ). Adequate page space for case study description would contribute to better publications (Gillard et al., 2011 ). Capitalizing on the ability to publish complementary resources should be considered.

Limitations of the review

There is a level of subjectivity involved in this type of review and this should be considered when interpreting study findings. Qualitative methods journals were selected because the aims and scope of these journals are to publish studies that contribute to methodological discussion and development of qualitative research. Generalist health and social science journals were excluded that might have contained good quality case studies. Journals in business or education were also excluded, although a review of case studies in international business journals has been published elsewhere (Piekkari et al., 2009 ).

The criteria used to assess the quality of the case studies were a set of qualitative indicators. A numerical or ranking system might have resulted in different results. Stake's ( 1995 ) criteria have been referenced elsewhere, and was deemed the best available (Creswell, 2013b ; Crowe et al., 2011 ). Not all qualitative studies are reported in a consistent way and some authors choose to report findings in a narrative form in comparison to a typical biomedical report style (Sandelowski & Barroso, 2002 ), if misinterpretations were made this may have affected the review.

Case study research is an increasingly popular approach among qualitative researchers, which provides methodological flexibility through the incorporation of different paradigmatic positions, study designs, and methods. However, whereas flexibility can be an advantage, a myriad of different interpretations has resulted in critics questioning the use of case study as a methodology. Using an adaptation of established criteria, we aimed to identify and assess the methodological descriptions of case studies in high impact, qualitative methods journals. Few articles were identified that applied qualitative case study approaches as described by experts in case study design. There were inconsistencies in methodology and study design, which indicated that researchers were confused whether case study was a methodology or a method. Commonly, there appeared to be confusion between case studies and case reports. Without clear understanding and application of the principles and key elements of case study methodology, there is a risk that the flexibility of the approach will result in haphazard reporting, and will limit its global application as a valuable, theoretically supported methodology that can be rigorously applied across disciplines and fields.

Conflict of interest and funding

The authors have not received any funding or benefits from industry or elsewhere to conduct this study.

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Differentiating Lyme arthritis: a case-based review

• Case Based Review
• Published: 25 May 2024

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• Ayse Mine Unlu   ORCID: orcid.org/0000-0002-5541-0184 1 , 6 ,
• Nanna Skaarup Andersen   ORCID: orcid.org/0000-0002-3927-9294 2 , 3 , 4 ,
• Sanne Løkkegaard Larsen   ORCID: orcid.org/0000-0003-1923-9890 2 , 3 , 4 ,
• Sigurdur Skarphedinsson   ORCID: orcid.org/0000-0001-8440-7040 4 , 5 ,
• Stavros Chrysidis   ORCID: orcid.org/0000-0001-8583-6517 1 ,
• Fredrikke Christie Knudtzen   ORCID: orcid.org/0000-0001-8348-7819 2 , 5 &
• Philip Rask Lage-Hansen   ORCID: orcid.org/0000-0002-1449-254X 1  

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The incidence or prevalence of Lyme arthritis (LA) in Denmark is unknown and assumed very low. No published cases of polymerase chain reaction (PCR)-confirmed LA from Denmark exist. Clinically, LA does not differ from other rheumatic oligoarthritic disorders posing a differential diagnostic challenge. To review the incidence and prevalence of LA to our knowledge and to present a case series of PCR-confirmed LA cases from Denmark. We conducted a systematic literature review via MEDLINE and EMBASE to explore incidence and prevalence rates of LA. Additionally, we present six cases of patients diagnosed with LA in Denmark. Our literature review identified 23 studies reporting prevalence or incidence, yet only ten studies provided estimates ranging from 1.1 to 280/100.000 in the general population. Our case series identified six patients with LA from a localized region in Southern Denmark; all confirmed by Borrelia -specific real-time PCR from synovial fluid. The diagnostic delay was up to 38 months. All patients except one had a history of previous tick bites; none had erythema migrans lesions. All presented with recurrent arthritis in the knee joint, and two had arthritis in the wrist. The literature review showed an incidence of LA ranging from 1.1 to 15.8 per 100.000 in Europe. Our case series suggests a potentially higher prevalence of LA in Denmark than previously believed. Lack of tick exposure history, antibody assessments and test of Borrelia burgdorferi sensu lato DNA in synovial fluid might lead to misdiagnosed cases potentially explaining the assumed low incidence of LA in Denmark.

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Acknowledgements

The authors would like to thank the patients for participating in this case series and the clinicians and technicians at Department of Rheumatology, Microbiology, and Infectious Disease for their involvement in diagnostics and treatment.

The study was conducted without any funding.

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Ayse Mine Unlu, Stavros Chrysidis & Philip Rask Lage-Hansen

Clinical Center for Emerging and Vectorborne Infections, Odense University Hospital, Odense, DK-5000, Denmark

Nanna Skaarup Andersen, Sanne Løkkegaard Larsen & Fredrikke Christie Knudtzen

Department of Clinical Microbiology, Odense University Hospital, Odense, DK-5000, Denmark

Nanna Skaarup Andersen & Sanne Løkkegaard Larsen

Clinical Microbiology research unit, University of Southern Denmark, Odense, Denmark

Nanna Skaarup Andersen, Sanne Løkkegaard Larsen & Sigurdur Skarphedinsson

Department of Infectious Diseases Q, Odense University Hospital, Odense, DK-5000, Denmark

Sigurdur Skarphedinsson & Fredrikke Christie Knudtzen

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Ayse Mine Unlu and Philip Rask Lage-Hansen contributed to the study’s conception and design. Ayse Mine Unlu conducted the systematic literature search, screened the retrieved records, and created the flowchart and table. Ayse Mine Unlu and Philip Rask Lage-Hansen drafted the initial manuscript. Clinicians (Nanna Skaarup Andersen and Sanne Løkkegaard Larsen) from the Department of Clinical Microbiology described and conducted the B.b. s.l. specific PCR analyses. Philip Rask Lage-Hansen and Stavros Chrysidis diagnosed the patients in this case series, with Sigurdur Skarphedinsson consulted regarding antibiotic treatment in all cases. All authors critically reviewed and contributed substantially to the manuscript’s refinement. All authors take full responsibility for the integrity and accuracy of all aspects of the work.

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Unlu, A.M., Andersen, N.S., Larsen, S.L. et al. Differentiating Lyme arthritis: a case-based review. Rheumatol Int (2024). https://doi.org/10.1007/s00296-024-05618-0

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Surgical intervention of Lemierre’s syndrome: a case report and review of the literature

• Yiqi Pan 1   na1 ,
• Zhihong Shi 1   na1 ,
• Qian Da 2 ,
• Chaofu Wang 2 ,
• Yilin Shen 1 &
• Mingliang Xiang   ORCID: orcid.org/0000-0001-9253-9852 1  

Journal of Medical Case Reports volume  18 , Article number:  265 ( 2024 ) Cite this article

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Lemierre’s syndrome is a fatal and rare disease that is typically characterized by oropharyngeal infection and internal jugular vein thrombosis. Timely institution of appropriate antibiotics is the standard treatment.

Case presentation

The authors report a case of Lemierre’s syndrome. A 67-year-old male patient of Han ethnicity in China suffered from a large inflammatory neck mass involving left internal jugular vein thrombosis diagnosed as Lemierre’s syndrome and finally cured by surgical treatment. In addition, a literature review was carried out through PubMed using the terms “Lemierre’s syndrome/disease and review, meta-analysis or retrospective study” and “Lemierre’s syndrome/disease and internal jugular vein”. This search yielded six articles that recorded surgical methods such as drainage, craniotomy, tooth extraction, and ligation of the occluded vein to give clinicians more ideas about the treatment of the Lemierre’s syndrome.

This is the first review to summarize the conditions under which surgical treatment are conducted. Additionally, this is the first report of such a large inflammatory neck mass that was completely cured by surgical resection and internal jugular vein ligation. The authors also offer several conclusions regarding surgical intervention in Lemierre’s syndrome for the first time.

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Internal jugular vein (IJV) thrombosis is a relatively rare and urgent disease. In a retrospective study, the number of such cases occurring from 2001 to 2008 was 2.5 times that occurring from 1991 to 2000 and 20 times that occurring from 1980 to 1990 [ 1 ]. The reasons behind the increasing incidence of IJV thrombosis include the increase in antibiotic resistance, widespread use of hemodialysis, general application of central venous catheters, expansion of assisted reproductive technology, and increasing incidence of cancer [ 2 ]. In a 9-year retrospective study of 1948 patients with deep vein thrombosis, only 29 patients developed IJV thrombosis, of whom 23 had IJV thrombosis secondary to another condition, such as a malignancy (for example, Trousseau syndrome), central venous catheter implantation, or ovarian hyperstimulation syndrome (OHSS) [ 3 ]. In addition, bilateral internal jugular vein thrombosis is an important indicator of malignant tumors. In a 5-year retrospective study of 41 patients with IJV thrombosis in Germany, paraneoplastic thrombosis accounted for 54% of cases; of these cases, otolaryngology head and neck diseases accounted for 68%. The other patients mostly had inflammatory diseases [ 4 ].

In the ear, nose, and throat (ENT) field, IJV thrombosis is commonly associated with Lemierre’s syndrome (LS), which is a complication of infectious diseases, such as otitis media and oropharyngeal abscess or infection. LS is commonly defined by the following diagnostic criteria: (1) oropharyngeal infection; (2) internal jugular vein thrombophlebitis or thrombosis; (3) septic emboli at a remote site, more frequently the lungs; and (4) isolation of Fusobacterium nucleatum on blood culture [ 5 ]. LS is usually accompanied by septic emboli in the lungs or other organs [ 6 ]. Under some rare conditions, LS can also be triggered by tooth extraction [ 7 ]. Pulmonary embolism, with an incidence of approximately 10%, and postthrombotic syndromes, such as limb pain, heaviness, venous dilatation, edema, pigmentation, nutritional skin changes, and venous ulcers, are complications of IJV thrombosis [ 4 ]. Therefore, ENT doctors should give enough attention to patients with IJV thrombosis to avoid the disastrous results caused by pulmonary or cerebral thrombosis.

To the best of our knowledge, this is the first case of such a large infectious neck mass with internal jugular vein thrombosis that was completely cured by surgical intervention.

A 67-year-old Chinese male of Han ethnicity developed pain in the left neck 14 days prior after eating mud fish. He was healthy and denied a history of infectious diseases, chronic diseases, thrombotic disease, surgical trauma, blood transfusion, allergies, or contact with poisonous substances. Physical examination on admission revealed the following: fever, chills, fatigue, mild dysuria, diffusive swelling pain of the neck on the left side, and high skin temperature. His left neck was tender and edematous with cellulitis. The mass was scleroid with a liquefied center. Other parameters were as follows: white blood cell (WBC) count, 12.2 × 10 9 /L; neutrophil count, 11.76 × 10 9 /L; platelet (PLT) count, 51 × 10 9 /L; C-reactive protein (CRP) level, 146 mg/L; procalcitonin (PCT), 156.99 ng/mL; temperature, 39.5 °C; respiratory rate, 24 breaths per minute; pulse, 118 beats per minute; and blood pressure (BP), 109/61 mmHg. The patient stated that he had been to many hospitals in the last 2 weeks and that the use of antibiotics such as ceftriaxone and metronidazole slightly alleviated his neck pain at first. However, the effect was temporary and no longer present after he transferred to Shanghai, and 3 days before he presented to our hospital, he noticed extreme swelling and felt increased pain in the area of his neck mass (Fig.  1 ). A series of further examinations were performed, with the following results: glucose, 22.13 mmol/L; activated partial thromboplastin time (APTT), 43.1 seconds; prothrombin time (PT), 17.3 seconds; fibrinogen (Fg), 5.0 g/L; fibrin/fibrinogen degradation products (FDP), 7.3 mg/L; and D-dimer (D-D), 2.1 mg/L. Urine analysis was positive for glucose, blood, protein, and white blood cells. Infectious diseases and acute nephrology were considered. The culture of blood and fluid obtained from the mass was negative for any bacteria including anaerobic bacteria, mycoplasma, or fungus. Ultrasound revealed mixed echogenicity in the left neck mass that was irregular in shape. The mass was approximately 74 × 37 mm in size. Color Doppler revealed generalized thrombosis of the internal jugular vein. CT of the chest and neck was conducted and suggested that the cervical abscess extended to the thorax and superior mediastinum, without a signal from the left internal jugular vein. Multiple enlarged cervical lymph nodes were observed. The trachea and left thyroid were also compressed (Fig.  2 ). Video laryngoscopy excluded the possibility of pyriform sinus fistula or any foreign body. Pus obtained from the mass showed many neutrophils and large amounts of necrotic tissue, and 14 days of combination antibiotic treatment (imipenem and teicoplanin) and regular insulin therapy in our hospital returned the patient’s temperature, routine blood markers, CRP and PCT levels, and coagulation function to normal. However, the neck mass remained. Therefore, the surgery department was consulted.

Picture of the patient’s neck showed a huge mass with tenderness (red circles)

A Coronal plane of computed tomography showed neck mass spread down to superior mediastinum with iquefactive necrosis in the center (red arrows). Trachea was oppressed to the right side. B Significant intraluminal filling defect and thrombosis was found in internal jugular vein (yellow arrow)

The patient was taken to the operating room. The neck mass adhered tightly to the surrounding tissue, and the involved segment of the left internal jugular vein was exposed by sharp dissection (Fig.  3 A). The proximal part of the mass needed to be ligated first to avoid small thrombus detachment. There was a large amount of inflammation and fibrosis present in the involved area. The involved segment of the internal jugular vein and the whole neck mass were completely resected, and the distal part of the internal jugular vein was fully ligated (Fig.  3 B). The pathological examination showed hemorrhagic necrosis with the proliferation of fibrous and granulation tissue and the accumulation of foam-like cells and multinuclear giant cells (Fig.  4 ). The patient recovered and was discharged a week after surgery. No other adverse events happened.

Intraoperative view showed ligation of internal jugular vein and separation of the mass ( A ). The resected neck mass as well as left internal jugular vein was shown. Intraluminal thrombosis could be seen clearly when opening the internal jugular vein ( B )

Representative pathological photomicrograph demonstrated thrombus ( A ) and abscess formation ( B )

Literature review

It is rare that patients with Lemierre’s syndrome require surgical intervention when antibiotics and anticoagulant therapies fail. This is the first study to summarize cases of LS requiring surgical treatment (not including abscess drainage). First, we decided to collect previous reviews and meta-analyses to obtain good knowledge of the rate of surgery in LS. Search strategy and selection criteria were as follows. A search of the literature in MEDLINE was performed through PubMed to identify relevant English language articles from 1980 to 2022. The following search terms were used: “Lemierre’s syndrome/disease and review, meta-analysis or retrospective study” and “Lemierre’s syndrome/disease and internal jugular vein”. The references of the retrieved articles were also reviewed to identify additional sources. Through reading the abstract and the full text, we found a total of six reviews and meta-analyses (Table  1 ) that included detailed descriptions of patients who underwent surgery (not including abscess drainage). In a retrospective review from 1998 to 2010 at a local tertiary referral hospital, 17 of the 23 patients underwent surgical treatment of the primary infection site [ 8 ]. In a 5-year systematic review, surgical procedures, such as tooth extraction, craniotomy, and ligation of the occluded vein, were performed in five patients to prevent further septic emboli [ 9 ]. A retrospective study from June 2000 to May 2016 showed that IJV ligation was performed in only one of five LS cases at the Children’s Hospital of Alabama [ 10 ]. In an 8-year Swedish nationwide retrospective study, three patients with peritonsillitis were surgically treated by tonsillectomy [ 11 ]. In the latest meta-analysis of 394 patients in 2020, only 10 patients underwent IJV ligation/excision, only 1 patient underwent ligation/excision of the thrombosed external carotid artery, 3 underwent endoscopic sinus surgery, and 11 underwent mastoidectomy [ 12 ]. In the latest systematic review, which included the most LS cases reported, surgical procedures were performed in 101 patients, and 31 patients underwent IJV ligation/embolectomy [ 13 ].

In this study, we report a case of Lemierre’s syndrome in an elderly male caused by an acute infectious neck mass. Timely comprehensive medical and surgical treatments were given to avoid serious complications.

Internal jugular vein thrombosis is a rare and serious emergent disease that needs to be identified early in the course, as it can lead to catastrophic consequences, such as stroke or pulmonary embolism. The main pathological basis of internal jugular vein thrombosis is as follows: (1) injury of venous intima; (2) slowing down of blood flow; and (3) hypercoagulability. The common causes are as follows [ 14 , 15 , 16 ]: (1) facial infection, such as furuncle and carbuncle, sinusitis, otitis media, and suppurative tonsillitis; bacteria can spread through the damaged mucosa and parapharyngeal space or invade the jugular vein through the lymphatic and venous systems, leading to infectious phlebitis and bacterial embolism information; (2) long duration of internal jugular vein catheterization; (3) head and neck surgery; (4) head and neck tumor; (5) pulmonary embolism; and (6) other systemic diseases, such as polycythemia. Doctors need to take care of patients immediately when encountering such cases.

Lemierre’s syndrome can show the typical symptoms and signs of progressive infection, including sore throat, fever, or neck pain. A systematic review of Lemierre’s syndrome by Peter et al . found that in 84 patients, the most common first clinical presentation was a sore throat (33%), followed by a neck mass (23%) and neck pain (20%) [ 1 ]. In the current case, the patient presented with fever and neck pain at first, followed by a neck mass. The use of antibiotics before he was transferred to our hospital was ineffective. The white blood cell count, PCT level, and erythrocyte sedimentation rate (ESR) were elevated, and blood appeared in his urine. We adjusted the treatment to the combined application of broad-spectrum antibiotics, including imipenem and teicoplanin, for another 2 weeks. The patient’s body temperature returned to normal and laboratory testing showed that the patient’s infectious condition had been controlled, but the neck mass and internal jugular vein thrombosis persisted and required surgical treatment.

Fusobacterium necrophorum is the main pathogen of Lemierre’s syndrome [ 1 ]. However, in this case, the culture of both blood and fluid obtained from the mass was negative for bacteria, which might be because the patient had been treated with antibiotics (mainly including ceftriaxone and metronidazole) for nearly 2 weeks before coming to our hospital. This also suggests that it is particularly important for doctors to culture blood or fluid from the mass before any use of antibiotics in these patients. In many reviews, a large proportion of the cases also did not report any microbiological agent [ 9 , 12 , 13 ] and thus far a clinical diagnosis of LS is still valid if the bacteria go undetected. As for the reason about how this patient got such infectious disease, considering that he had eaten mud fish before the onset of disease and CT showed that mucous of left pyriform sinus was edematous and enhanced (Fig.  5 ), we considered that neck infection might be secondary to the infection of mucous scratch in left pyriform sinus, and uncontrolled hyperglycemia was an important factor to cause serious infection.

Coronal plane of computed tomography showed disappearance of left pyriform sinus surrounding by abnormal enhancement (yellow arrow)

The diagnosis of internal jugular vein thrombosis in Lemierre’s syndrome relies on imaging examination. Ultrasound is the first choice for the diagnosis of LS, and CT and magnetic resonance imaging (MRI) are currently implemented in general practice when necessary. Albertyn et al . first summarized the classic imaging features of internal jugular vein thrombosis. Ultrasonography shows the vein to be distended and nonpulsatile, with internal echoes. CT shows swelling of the adjacent soft tissues, distension of the vein with wall enhancement, and low-attenuation intraluminal filling defects. However, ultrasound has limitations and cannot display the anatomy behind the clavicle or mandible [ 16 ]. In this case, we found that although US can clearly show internal jugular vein thrombosis, knowing its boundaries and connection with the tumor still depends on CT or MRI, especially when there is an urgent need for surgery. A full assessment by preoperative imaging is of great importance. This is also consistent with the views of Charles et al . [ 17 ].

Priority treatment for LS includes antibiotic therapy and drainage of the infected site. Here in our hospital, considering that cephalosporins such as ceftriaxone did not control the fever and pain in this patient, imipenem and teicoplanin were used according to experience to cover wide varieties of Gram-negative and Gram-positive bacteria, including both anaerobic and aerobic bacteria. In addition, teicoplanin has lower side effects than vancomycin [ 18 ]. Rarely, other surgical procedures, such as ligation of the occluded vein, craniotomy, and tooth extraction, are performed. Antithrombotic therapy, including novel oral anticoagulants (DOACs), is also recommended depending on the individual’s condition. However, it remains controversial whether anticoagulation or antithrombotics are effective in Lemierre’s syndrome. Some scholars think that thrombosis is due to the infection process and can be resolved when the infection has been controlled [ 19 ]. In this case, we did not immediately apply anticoagulant or thrombolytic therapies considering that the APTT of this patient was significantly prolonged at the time he came to our hospital and the consumption of platelets was relatively high; emergency anticoagulant therapy may have increased his risk of bleeding. To date, there have been no sufficient clinical studies and no sufficient evidence suggesting the necessity for anticoagulant therapy in Lemierre’s syndrome [ 20 ]. Previous studies have also reported the occurrence of extensive suppurative thrombophlebitis of the bilateral IJV and superior vena cava in patients with Lemierre’s syndrome despite the use of antibiotics and anticoagulant therapy; adjunctive catheter-directed thrombolysis and superior vena cava stenting were performed to help these patients completely recover [ 21 ]. Anticoagulation therapy has not been shown to reduce the complications of Lemierre’s syndrome, such as sepsis [ 17 ]. Meanwhile, Johannesen et al . did not find that anticoagulation therapy decreased the mortality rate or course of the disease or reduced the duration of antibiotic use [ 9 ]. However, anticoagulation therapy is recommended in patients with a poor clinical response despite antibiotic therapy and with a high risk of intracranial thrombosis or recurrent thrombophlebitis [ 22 , 23 , 24 ]. In this case, the cause of internal jugular vein thrombosis was largely infection, so surgical treatment was the best choice when antibiotics could not completely cure the infection and thrombosis. Through previous retrospective studies, systematic reviews and meta-analyses obtained by database searches, we summarized the following points regarding surgical intervention in Lemierre’s syndrome:

When patients do not respond to conservative medical therapy and continue to show extensive septic thrombosis or uncontrolled severe sepsis, surgical treatments need to be considered.

Abscess drainage is the most common and convenient surgical treatment for abscesses upon formation.

Surgical treatment of the primary infection site is effective for controlling the spread of infection and sepsis.

IJV ligation or excision is suitable for patients with persistent septic embolization after treatment with antibiotics and anticoagulants.

IJV ligation or excision is also appropriate to avoid thrombus detachment when anticoagulation therapy or catheter-directed thrombolysis is ineffective.

Lemierre’s syndrome is an extremely rare disease, but the fatality rate can reach 15%, even with escalating antibiotic therapy [ 21 ] . Therefore, early diagnosis is particularly important, and the timely institution of appropriate antibiotics is the standard treatment. Surgical intervention may be the only effective option for controlling the source of infection or when conservative medical treatment fails.

Availability of data and materials

Available from corresponding author on reasonable request.

Abbreviations

Internal jugular vein

Ear, nose, and throat

• Lemierre’s syndrome

White blood cell

C-reactive protein

Procalcitonin

Blood pressure

Computed tomography

Magnetic resonance imaging

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Acknowledgements

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This study was supported by the National Natural Science Foundation of China (grant nos. 82101212, 82101209, 82301296, 82301297), Science and Technology Commission of Shanghai Municipality (grant nos. 23ZR1440200, 21ZR1440200, SHDC2020CR1044B-003), Shanghai “Rising Stars of Medical Talents” Youth Development Program, and Shanghai Municipal Hospital ENT Specialist Alliance.

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Yiqi Pan and Zhihong Shi contributed equally to this work.

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Department of Otolaryngology and Head and Neck Surgery, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Yiqi Pan, Zhihong Shi, Bin Ye, Yilin Shen & Mingliang Xiang

Department of Pathology, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China

Qian Da & Chaofu Wang

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Mingliang Xiang performed the whole operation and checked the final review. Yilin Shen revised and reviewed the original manuscript. Yiqi Pan wrote the whole manuscript. Zhihong Shi took part in the whole operation and carried out the literature review. Bin Ye reviewed the manuscript. Chaofu Wang and Qian Da provided the pathological images. All authors read and approved the final manuscript.

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Pan, Y., Shi, Z., Ye, B. et al. Surgical intervention of Lemierre’s syndrome: a case report and review of the literature. J Med Case Reports 18 , 265 (2024). https://doi.org/10.1186/s13256-024-04584-2

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CASE REPORT article

Omalizumab in combination with subcutaneous immunotherapy for the treatment of multiple allergies associated with attention-deficit/hyperactivity disorder: a case report and a literature review.

• Department of Pediatrics, Renji Hospital, Shanghai Jiaotong University School of Medicine, Shanghai, China

We describe the case of a 10-year-old boy with asthma (AS), accompanied by allergic rhinitis (AR), food allergy (FA), and combined attention-deficit/hyperactivity disorder (ADHD), who was treated at Shanghai Renji Hospital on 11 July 2020. The efficiency of the previous treatment with salmeterol/ticlosone was poor. Treatment with montelukast sodium resulted in development of neurological symptoms. Treatment with omalizumab in combination with subcutaneous immunotherapy (SCIT) was then initiated in our department based on anti-asthmatic therapy. Symptoms of asthma were completely controlled, and FA and AR symptoms improved. The treatment regimen led to a significant improvement in ADHD symptoms and the overall quality of life of the patient. The literature search was done in the PubMed database using “attention deficit/hyperactivity disorder/ADHD” and “asthma” as keywords, and we identified 47 relevant articles. In conclusion, our results show that treating asthma with omalizumab in combination with salmeterol/ticlosone and SCIT is efficient in controlling symptoms of multiple allergies and may lead to the improvement in ADHD symptoms and the overall quality of life of pediatric patients with ADHD. While current studies suggest that allergic diseases are closely related to ADHD, there is still a lack of studies or case reports of complete treatment protocols to provide clinical clues for management of the disease.

Introduction

Half of the global population is expected to develop allergic diseases in 2050 ( Cecchi et al., 2018 ; Ren et al., 2022 ). Asthma (AS) is one of the most prevalent childhood-onset allergic diseases that arises due to a combination of environmental and genetic factors and is manifested as a chronic inflammation state with reversible constriction of the airways ( Leffa et al., 2021 ). Asthma is characterized by symptoms such as recurrent cough, wheezing, and shortness of breath ( Yuksel et al., 2008 ; Sun et al., 2021 ) that profoundly impact patients’ quality of life.

Attention-deficit/hyperactivity disorder (ADHD) is considered the most common neurodevelopmental and behavioral pediatric disease ( Zhou et al., 2019 ) and manifests as a high level of inattention, hyperactivity, impulsive behavior, learning disabilities, sleep disturbances, and, often, social isolation ( Bonvicini et al., 2016 ; Chai et al., 2021 ). The prevalence of ADHD in children is approximately 7.2%, with 50% of cases persisting into adulthood ( Developmental Behavioural Group of the, 2020 ).

The correlation between ADHD and inflammatory and autoimmune diseases, including asthma, has long become a focus of attention. Recent studies suggested that ADHD patients are more likely to present with asthma, allergic rhinitis (AR), allergic conjunctivitis, atopic dermatitis, and psoriasis ( Wang et al., 2018a ; Chang et al., 2021 ). Studies also show that various inflammation-associated genes and inflammatory mechanisms play a role in the occurrence of ADHD ( Leffa et al., 2018 ; Wong et al., 2022 ). For example, increased interleukin-6 (IL-6) levels may impact neural pathways, neurogenesis, and synaptic plasticity in the prefrontal cortex and hippocampus of pediatric patients ( Hunter and Jones, 2015 ). Current evidence suggests that respiratory allergic diseases have a high probability of comorbidity with eczema and food allergies ( Pols et al., 2015 ; Esteban-Gorgojo et al., 2021 ; Laidlaw et al., 2021 ), which further increases the risk of ADHD ( Shyu et al., 2012 ). Research also demonstrated the effectiveness of subcutaneous immunotherapy (SCIT) therapy in alleviating ADHD symptoms in children with difficult-to-treat ADHD ( Yu et al., 2023 ).

ADHD patients with allergic diseases often have difficulties in effective self-management, which increases the complexity of allergic disease treatment, prolongs the course of the disease, reduces the quality of life, and seriously affects children’s growth and development as well as their physical and mental health ( Jin et al., 2021 ; Ren et al., 2022 ). In this study, we report the case of a pediatric patient with multiple allergic diseases and ADHD, treated with omalizumab and SCIT. Additionally, we performed a literature search to identify studies that describe the connection between ADHD and allergic diseases in the pediatric population. Together with the existing literature, our observations may contribute to deepening the understanding of the clinical characteristics of allergic diseases and provide potential clinical ideas for the diagnosis and treatment of such patients.

Case presentation

Patient information and medical history.

We present the case of a male child, 10 years old, admitted to Shanghai Renji Hospital on 11 July 2020 because of “recurrent wheezing for 8 years,” with the diagnosis of allergic asthma, allergic rhinitis, food allergy, ADHD (combined type), and intellectual disability. Written informed consent was obtained from the patient.

The child was gravida 2 para 1, full term, delivered by Cesarean section, with no history of choking resuscitation, mixed feeding, and immunizations on time. The child had a history of recurrent eczema (disappeared at 1.5 years), was talking at 2 years, and had rhinitis at 3 years.

History of neurodevelopmental disorder

At 8 years, the child was diagnosed with intellectual disability and combined ADHD and was treated with methylphenidate hydrochloride, but the symptoms of ADHD were not effectively controlled. The patient did not undergo cognitive behavioral therapy (CBT). Eventually, the child discontinued the drug on his own and was not taking any ADHD medications upon admission.

History and symptoms of allergic disease

The patient had a family history of allergic diseases (both parents and sister are allergic). Wheezing first manifested at the age of 1.5 years. The child suffered from recurrent respiratory infections from birth to 2 years of age. Wheezing occurred over six times/year after the age of 3 and was induced by cold air, exercise, rainy weather, and emotional changes. Cough was dry, occurred in the absence of respiratory infection, was induced by cold air, and predominantly occurred at night. There was no evidence of fever, foreign body aspiration, hoarseness, chest tightness, sighing, acid reflux, belching, early satiety, night sweats, lethargy, hemoptysis, and nocturnal sleep snoring during the entire course of the illness. Asthma was accompanied by food allergies to eggs and fish (rash, itching, and cough after eating) and to azithromycin.

Initial presentation, diagnostic tests, and treatment

A physical examination revealed the following characteristics of the patient: height, 130 cm; weight, 30 kg; hyperactive; the nasal mucosa was slightly pale with edema; and a small amount of clear mucus; double-lung auscultation respiratory sounds were thick with mild wheezing and no wet rales. Heart, abdomen, and nervous systems were normal.

The blood routine detected the following: eosinophils (EOSs), 5.6%; total immunoglobulin E (IgE), 3,380 (IU/mL); household dust mite immunoglobulin E (IgE), 19.3 IU/mL; and mixed mold IgE, 24.3 IU/mL.

Pulmonary function tests and chest computed tomography (CT) detected no abnormalities.

History of treatment

At 8 years of age, the patient underwent treatment with a nebulizer containing budesonide suspension for inhalation, two times a day for 2 months, but discontinued the medication on his own after improvement. At 9.5 years of age, the patient had a severe asthmatic attack with progressive restriction of movement and recurrent episodes of wheezing. At the age of 10, treatment with inhaled corticosteroid (ICS)/long-acting beta agonist (LABA) was initiated: ICS (ticlosone; 100 mg) and LABA (salmeterol; 50 mg) inhalations. However, due to the long duration of asthma and poor ICS–LABA administration control, the treatment was not effective in controlling the symptoms. Oral leukotriene receptor antagonist (LTRA) montelukast sodium (one sachet, once a day) was added, but the patient reported a state of euphoria throughout the day, which resolved after ICS–LABA–LTRA treatment was discontinued.

After the diagnosis upon admission, the following treatment was initiated, as shown in Figure 1 : a child received initial treatment with ICS (ticlosone; 100 mg) + LABA (salmeterol; 50 mg) + omalizumab (150 mg). ICS + LABA was initially used in the morning and evening, one inhalation per time; after 9 months of treatment, the ICS + LABA dosage was reduced to once a day, one inhalation per time; after 18 months of treatment, inhalations were performed every 2 days, one inhalation per time. The initial omalizumab dosage was 150 mg/month. Starting from 18 months, the dosage was changed to 150 mg/2 months up to 24 months of follow-up. The patient reported no side effects.

Figure 1 . Flowchart of the treatment regimen. The patient was started on the ICS, LABA, and omalizumab treatment, and SCIT therapy was initiated 6 months after the beginning of the treatment. SCIT: subcutaneous immunotherapy; ICS: inhaled corticosteroid; LABA: long-acting beta-agonist.

SCIT was initiated 6 months after the beginning of ICS/LABA/omalizumab treatment. Mite allergen-specific immunotherapy was carried out by subcutaneous injections of the high-dose house dust mite allergoid (Alutard SQ, Denmark), which is provided in the form of four injectable vials with the following concentrations: 100 SQ-U/mL for vial 1; 1,000 SQ-U/mL for vial 2; 10,000 SQ-U/mL for vial 3; and 100,000 SQ-U/mL for vial 4. The dose escalation rules were as follows:

Vial 1: 0.2 mL, 0.4 mL, and 0.8 mL (1–3 weeks).

Vial 2: 0.2 mL, 0.4 mL, and 0.8 mL (4–6 weeks).

Vial 3: 0.2 mL, 0.4 mL, and 0.8 mL (7–9 weeks).

Vial 4: 0.1 mL, 0.2 mL, 0.4 mL, 0.6 mL, 0.8 mL, and 1.0 mL (10–15 weeks).

In the first 15 weeks, the injections were administered once a week. After 15 weeks, injections were administered once a month. Each injection had a dose of 1.0 mL ( Figure 1 ). On the 12-month visit, the patient reported wheezing after the desensitization treatment. The follow-up history revealed that ICS had been discontinued on its own. Self-discontinuation or self-reduction of medication can lead to a state of uncontrolled asthma ( Rogers and Reibman, 2012 ). Therefore, it is plausible that due to the predominantly allergic nature of asthma, a patient who discontinues the medication on their own while being exposed to high concentrations of mite allergens during SCIT can eventually develop an acute asthma attack. The child was instructed to resume regular medication, and the symptoms resolved.

The recorded patient outcomes included subjective improvement, rhinitis symptoms, asthma symptoms, quality of life, and food allergies.

Asthma severity was assessed using the Childhood Asthma Control Test (CACT), a childhood asthma control tool with seven questions. The first four questions have a score range of 0–3, and the last three questions have a score range of 0–5, for a total score of 27. The scores were as follows: score ≤19, uncontrolled asthma; 20–22, partially controlled; and ≥23, well-controlled ( Liu et al., 2007 ).

Additionally, asthma symptoms and allergic rhinitis symptoms were assessed using the visual analog scale (VAS) score, a subjective visual analog scale that rates rhinitis or asthma symptoms, with a score of 0 representing no symptoms and 10 representing the most severe symptoms ( Bousquet et al., 2007 ). Symptom scores were assessed based on the severity of the main symptoms of asthma/rhinitis (asthma assesses cough, wheezing, shortness of breath, and chest tightness, and rhinitis assesses nasal congestion, itchy nose, runny nose, and sneezing). The classifications were as follows: none, no symptoms; mild, symptoms are mild and easily tolerated; moderate, symptoms are noticeable and annoying but tolerable; and severe, symptoms are intolerable and interfere with daily life or sleep ( Zhonghua, 2022 ).

The quality of life was assessed using the Pediatric Asthma Quality of Life Questionnaire (PAQLQ), which consists of 23 questions, each rated on a scale of 1–7 ( Sztafińska et al., 2017 ), with higher scores indicative of a better quality of life.

ADHD symptoms were assessed according to the Diagnostic and Statistical Manual of Mental Disorders—Fourth Edition (DSM-IV) ( Pappas, 2006 ) and Swanson, Nolan, and Pelham Rating Scale (SNAP-IV-18), an 18-question reporting inventory designed to measure attention deficit/hyperactivity disorder (ADHD) ( Swanson et al., 2001 ).

The ambient Air Quality Composite Index (AQCI) was used to assess the comprehensive condition of urban ambient air quality. The AQCI considers the pollution degree of six pollutants, namely, SO 2 , NO 2 , PM10, PM2.5, CO, and O 3 . A higher value of the AQCI indicates a heavier pollution degree.

As shown in Table 1 , after 6–9 months of omalizumab treatment, AR, asthma symptoms, and food allergy were basically controlled. A 12-month follow-up showed that the child developed wheezing after SCIT treatment. Blood work ( Table 2 ) showed a continuous marked improvement with progression of the treatment, with an almost twofold decrease in the white blood count (WBC) levels, and an eightfold decrease in the EOS levels (%) 24 months after the beginning of the ICS/LABA treatment, which corresponds to the 18 months after the beginning of the SCIT treatment. Similarly, pulmonary function tests ( Table 3 ) demonstrated a marked improvement in the lung function of the patient.

Table 1 . Assessment of symptoms.

Table 2 . Blood and pulmonary function indexes.

Table 3 . Pulmonary function tests.

As shown in Table 4 , after the treatment, ADHD symptoms and the quality of life of the patient markedly improved.

Table 4 . Progression of ADHD symptoms.

Environmental air quality was continuously monitored throughout the entire course of the treatment ( Table 5 ), and no marked fluctuations in the levels of pollutants were detected.

Table 5 . Local environmental situation during the course of the treatment

Literature review

We searched PubMed, Embase, and Chinese Medical Association Journal full-text databases using the keywords “asthma” and “ADHD/Attention-Deficit Hyperactivity Disorder.” We also searched the Chinese Medical Association Journal Network using the keywords “asthma” and “ADHD.” The initial search identified 47 articles related to asthma and ADHD in children.

This study reported a case of asthma with ADHD in a pediatric patient with a poorly controlled condition who was treated with the basic ICS + LABA regimen. Our study showed that omalizumab/SCIT treatment led to significant alleviation of asthma symptoms and related allergic comorbidities and was associated with a marked improvement of ADHD in the patient. The effect of the treatment in our study was not affected by the changes in the levels of environmental pollutants.

While ICS therapy is considered a cornerstone of the pharmacological treatment of asthma ( The Subspecialty Group of Respiratory DiseasesEditorial Board and Chinese Journal of Pediatrics, 2016 ), numerous studies emphasize the importance of the appropriate control of inhaled hormones and assessment of comorbidities in asthma patients ( Tajdini et al., 2019 ; Eyerich et al., 2020 ). However, ADHD patients with allergic diseases often have difficulties in effective self-management, which increases the complexity of allergic disease treatment, prolongs the course of the disease, reduces the quality of life, and seriously affects growth and development, as well as the physical and mental health of the affected pediatric patients ( Jin et al., 2021 ; Ren et al., 2022 ).

In the case described in our study, the child was initially treated with ICS + LABA + LTRA. However, due to neuropsychiatric symptoms, LTRA treatment was discontinued, and the overall achieved control of AS was poor. Omalizumab, a monoclonal antibody against human IgE, can be used for moderate-to-severe persistent allergic asthma in children 6 years and older with asthma uncontrolled by ICS + LABA therapy alone ( The Respiratory AllergyAsthma Group of Chinese Thoracic Society and Chinese Medical Association, 2019 ). The treatment regimen of the patient in the current study was, therefore, adjusted to ICS + LABA + omalizumab, which resulted in good asthma control and significantly improved quality of life. Omalizumab can be considered a first-line treatment in patients with early-onset allergic asthma with a history of allergies and/or clinically significant IgE >100 IU/mL with allergic rhinitis and moderately elevated fractional exhaled nitric oxide (FeNO) (50 ppd) ( Eyerich et al., 2020 ). Currently, the baseline IgE range for omalizumab treatment is 30–1,500 IU/mL. Although the guidelines do not recommend omalizumab for patients with a total IgE >1,500 IU/mL, some studies have shown that the use of omalizumab in pediatric asthma patients with high levels of IgE can help children achieve asthma control and reduce acute attacks with some degree of clinical benefit ( Maselli et al., 2013 ; Wang et al., 2018b ; Hutyrová et al., 2018 ; National Clinical Medical, 2021 ). In our study, using omalizumab resulted in rapid improvement of asthma and other IgE-mediated concomitant allergic symptoms (allergic rhinitis and food allergy) and reduced the use of hormones and associated medications ( Hutyrová et al., 2018 ; Liu and Yin, 2019 ). However, it is important to note that while we reported poor AS control using the ICS + LABA regimen, this outcome may be directly related to ADHD diagnosis of the child and poor compliance with the treatment. The effect of ICS + LABA is mainly affected by two things: frequency of dosing and ability to administer the medication correctly. In this study, the child’s compliance with the doctor’s instructions for medication dosing was confirmed using a hospital case system during a follow-up consultation and by checking with the parents before administering omalizumab injection treatment. However, because of ADHD, the patient was unable to cooperate with deep inhalation of the drug and sufficient breath-holding after the inhalation. This is consistent with previous studies that showed that poor compliance with ICS + LABA (such as insufficient frequency of the treatment and poor quality of administration) may directly affect the efficiency of the treatment ( Makhinova et al., 2015 ; Averell et al., 2022 ).

Future studies are needed to validate our observations

In addition to recurrent uncontrolled asthma attacks, the patient in our study presented with allergic symptoms in infancy, multiple allergic and non-allergic comorbidities, and significantly elevated total IgE levels, and mite and mold sIgE. Studies show that the onset of allergies is closely related to exposure to allergens or environmental factors ( Holgate, 1999 ; Kay, 2001 ; Galli et al., 2008 ). In agreement with these observations, in our study, the allergic symptoms of the patient were triggered by mites and molds, which are prevalent in the warm and humid climate of Shanghai and, therefore, make it difficult to control completely, ultimately leading to recurrent asthma attacks based on irregular asthma treatment.

Research shows that allergic asthma with allergen sensitization (mite allergen sensitization) is associated with an increased risk of ADHD ( Yang et al., 2018 ). This association of allergic diseases with ADHD was further confirmed by the results of our literature search. However, only few studies have reported on synergistic treatments and interventions for ADHD in children with asthma. Most studies, identified by our literature search, reported on the association of ADHD with allergic diseases. Tsai et al. (2014) showed that the 1-year prevalence of ADHD peaked at the ages of 6–11 years. In addition, the prevalence of asthma was significantly higher in the ADHD group. Jiang et al. found that airway allergic disease increases the risk of ADHD in children and is an independent risk factor of pediatric ADHD ( Jiang et al., 2017 ). Holmberg et al. demonstrated a relationship between the frequency of parent-reported asthma attacks and the probability of developing ADHD over 1 year ( Holmberg et al., 2015 ). It was reported that AS can increase core ADHD symptoms ( Lin et al., 2016 ), and that ADHD patients who were born premature and whose mothers experienced moderate-to-extreme stress during pregnancy had an increased risk of AS ( Grizenko et al., 2015 ). Genetic and environmental risk factors may collectively contribute to the onset and development of ADHD ( Cowell et al., 2019 ; Liu et al., 2019 ). Therefore, identifying modifiable neuropsychological risk factors for ADHD in early childhood can inform prevention strategies. Cowell et al. (2019) suggested that mother-specific responses are significantly associated with a greater risk of ADHD. Birth cohort studies have shown ( Liu et al., 2019 ) that 2.9% of children have ADHD and that the offspring of asthmatic parents are at an increased risk of ADHD. More specifically, the offspring of mothers with AS episodes during labor and prenatal and postnatal periods are at an increased risk of ADHD ( Pols et al., 2015 ).

Allergen sensitization may play a role in asthma and ADHD co-morbidity through neuroimmune pathways. While the exact mechanisms by which asthma influences the central nervous system (CNS) and vice versa are not known, there is evidence that chronic inflammatory conditions can lead to a disruption in the homeostasis of the neuroimmune environment ( Konstantinou et al., 2022 ). Potential mechanisms associated with asthma and ADHD ( Tsai et al., 2014 ; van der Schans et al., 2016 ; Chang et al., 2022 ; Gholami-Mahtaj et al., 2022 ; Jin et al., 2022 ) are possibly related to the effects of chronic allergic inflammation.

Numerous studies show that AS is a disease that is associated with type 2 cytokines, such as interleukin-4 (IL-4), IL-5, and IL-13, which promote AS symptoms such as airway eosinophilia, overproduction of mucus, bronchial hyperresponsiveness, and high levels of IgE ( Steinke and Borish, 2001 ; Kuruvilla et al., 2019 ; Wang et al., 2023 ). Similarly, symptoms of AR and food and skin allergies are induced by the acute, intermittent, or chronic type 2 (T2) inflammation and secretion of pro-inflammatory cytokines and eotaxins that can cross the blood–brain barrier, resulting in neuroinflammation ( Tamayo et al., 2024 ). Importantly, Guedes et al. (2023) demonstrated the impact of elevated IL-4 levels during cerebellar maturation and provided the first line of evidence for a mechanistical link between allergic disease and ADHD in humans. Additionally, mast cells express receptors for neuropeptides and neurotransmitters, thus playing a key role in the interplay between allergic diseases and neurological comorbidities ( Greene et al., 1985 ; Bienenstock et al., 1988 ; Stead et al., 1989 ; Kiernan, 1990 ; Williams et al., 1997 ), while IgE high-affinity receptors and other T2 receptors are expressed on sensory ( Kiernan, 1990 ) or enteric neurons and are functional and able to transmit signals to the CNS ( van der Kleij et al., 2010 ; Crosson et al., 2021 ). Taken together, these studies suggest that controlling environmental allergen exposure may help reduce the severity of ADHD and delay the disease progression and allergen immunotherapy ( Pelsser et al., 2009 ; Mi et al., 2020 ). Indeed, Yu et al. showed that SCIT therapy for AR improved ADHD outcomes in children with difficult-to-treat ADHD ( Yu et al., 2023 ). Previous studies show that SCIT in combination with omalizumab effectively increases patient tolerance during the initial dose-escalation phase, with 90% of patients achieving a maintenance dose. Addition of omalizumab reduced the risk of local and systemic reactions associated with SCIT treatment and improved patient adherence to the treatment ( Kuehr et al., 2002 ; Pfützner and Schuppe, 2021 ). Our results are consistent with these reports and demonstrate that the combination of ICS + LABA, omalizumab, and SCIT was effective in generating mite allergen immune tolerance and improving multiple allergies and ADHD-related symptoms.

In conclusion, we report a case of a pediatric patient with asthma and ADHD, who showed significant improvement in outcomes such as asthma control, associated comorbidities, quality of life, and ADHD symptoms after undergoing a treatment with omalizumab + SCIT on the basis of the ICS + LABA regimen. Taken together with the results of the literature search, our study provides some clues and a clinical basis for developing tailored treatment plans for children with allergic asthma in combination with ADHD.

Data availability statement

The original contributions presented in the study are included in the article/Supplementary Materials, further inquiries can be directed to the corresponding author.

Ethics statement

Written informed consent was obtained from the minor(s)’ legal guardian/next of kin for the publication of any potentially identifiable images or data included in this article.

Author contributions

BD: conceptualization, data curation, investigation, methodology, software, and writing–original draft. YL: conceptualization, data curation, methodology, project administration, software, validation, writing–original draft, and writing–review and editing.

The author(s) declare that no financial support was received for the research, authorship, and/or publication of this article.

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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Keywords: omalizumab, asthma, attention-deficit/hyperactivity disorder, subcutaneous immunotherapy, case report

Citation: Ding B and Lu Y (2024) Omalizumab in combination with subcutaneous immunotherapy for the treatment of multiple allergies associated with attention-deficit/hyperactivity disorder: a case report and a literature review. Front. Pharmacol. 15:1367551. doi: 10.3389/fphar.2024.1367551

Received: 08 January 2024; Accepted: 08 May 2024; Published: 03 June 2024.

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*Correspondence: Yanming Lu, [email protected]

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