synthesis of the reviewed literature

Literature Syntheis 101

How To Synthesise The Existing Research (With Examples)

By: Derek Jansen (MBA) | Expert Reviewer: Eunice Rautenbach (DTech) | August 2023

One of the most common mistakes that students make when writing a literature review is that they err on the side of describing the existing literature rather than providing a critical synthesis of it. In this post, we’ll unpack what exactly synthesis means and show you how to craft a strong literature synthesis using practical examples.

This post is based on our popular online course, Literature Review Bootcamp . In the course, we walk you through the full process of developing a literature review, step by step. If it’s your first time writing a literature review, you definitely want to use this link to get 50% off the course (limited-time offer).

Overview: Literature Synthesis

• What exactly does “synthesis” mean?
• Aspect 1: Agreement
• Aspect 2: Disagreement
• Aspect 3: Key theories
• Aspect 4: Contexts
• Aspect 5: Methodologies
• Bringing it all together

What does “synthesis” actually mean?

As a starting point, let’s quickly define what exactly we mean when we use the term “synthesis” within the context of a literature review.

Simply put, literature synthesis means going beyond just describing what everyone has said and found. Instead, synthesis is about bringing together all the information from various sources to present a cohesive assessment of the current state of knowledge in relation to your study’s research aims and questions .

Put another way, a good synthesis tells the reader exactly where the current research is “at” in terms of the topic you’re interested in – specifically, what’s known , what’s not , and where there’s a need for more research .

So, how do you go about doing this?

Well, there’s no “one right way” when it comes to literature synthesis, but we’ve found that it’s particularly useful to ask yourself five key questions when you’re working on your literature review. Having done so,  you can then address them more articulately within your actual write up. So, let’s take a look at each of these questions.

1. Points Of Agreement

The first question that you need to ask yourself is: “Overall, what things seem to be agreed upon by the vast majority of the literature?”

For example, if your research aim is to identify which factors contribute toward job satisfaction, you’ll need to identify which factors are broadly agreed upon and “settled” within the literature. Naturally, there may at times be some lone contrarian that has a radical viewpoint , but, provided that the vast majority of researchers are in agreement, you can put these random outliers to the side. That is, of course, unless your research aims to explore a contrarian viewpoint and there’s a clear justification for doing so. 

Identifying what’s broadly agreed upon is an essential starting point for synthesising the literature, because you generally don’t want (or need) to reinvent the wheel or run down a road investigating something that is already well established . So, addressing this question first lays a foundation of “settled” knowledge.

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2. Points Of Disagreement

Related to the previous point, but on the other end of the spectrum, is the equally important question: “Where do the disagreements lie?” .

In other words, which things are not well agreed upon by current researchers? It’s important to clarify here that by disagreement, we don’t mean that researchers are (necessarily) fighting over it – just that there are relatively mixed findings within the empirical research , with no firm consensus amongst researchers.

This is a really important question to address as these “disagreements” will often set the stage for the research gap(s). In other words, they provide clues regarding potential opportunities for further research, which your study can then (hopefully) contribute toward filling. If you’re not familiar with the concept of a research gap, be sure to check out our explainer video covering exactly that .

3. Key Theories

The next question you need to ask yourself is: “Which key theories seem to be coming up repeatedly?” .

Within most research spaces, you’ll find that you keep running into a handful of key theories that are referred to over and over again. Apart from identifying these theories, you’ll also need to think about how they’re connected to each other. Specifically, you need to ask yourself:

• Are they all covering the same ground or do they have different focal points  or underlying assumptions ?
• Do some of them feed into each other and if so, is there an opportunity to integrate them into a more cohesive theory?
• Do some of them pull in different directions ? If so, why might this be?
• Do all of the theories define the key concepts and variables in the same way, or is there some disconnect? If so, what’s the impact of this ?

Simply put, you’ll need to pay careful attention to the key theories in your research area, as they will need to feature within your theoretical framework , which will form a critical component within your final literature review. This will set the foundation for your entire study, so it’s essential that you be critical in this area of your literature synthesis.

If this sounds a bit fluffy, don’t worry. We deep dive into the theoretical framework (as well as the conceptual framework) and look at practical examples in Literature Review Bootcamp . If you’d like to learn more, take advantage of our limited-time offer to get 60% off the standard price.

4. Contexts

The next question that you need to address in your literature synthesis is an important one, and that is: “Which contexts have (and have not) been covered by the existing research?” .

For example, sticking with our earlier hypothetical topic (factors that impact job satisfaction), you may find that most of the research has focused on white-collar , management-level staff within a primarily Western context, but little has been done on blue-collar workers in an Eastern context. Given the significant socio-cultural differences between these two groups, this is an important observation, as it could present a contextual research gap .

In practical terms, this means that you’ll need to carefully assess the context of each piece of literature that you’re engaging with, especially the empirical research (i.e., studies that have collected and analysed real-world data). Ideally, you should keep notes regarding the context of each study in some sort of catalogue or sheet, so that you can easily make sense of this before you start the writing phase. If you’d like, our free literature catalogue worksheet is a great tool for this task.

5. Methodological Approaches

Last but certainly not least, you need to ask yourself the question: “What types of research methodologies have (and haven’t) been used?”

For example, you might find that most studies have approached the topic using qualitative methods such as interviews and thematic analysis. Alternatively, you might find that most studies have used quantitative methods such as online surveys and statistical analysis.

But why does this matter?

Well, it can run in one of two potential directions . If you find that the vast majority of studies use a specific methodological approach, this could provide you with a firm foundation on which to base your own study’s methodology . In other words, you can use the methodologies of similar studies to inform (and justify) your own study’s research design .

On the other hand, you might argue that the lack of diverse methodological approaches presents a research gap , and therefore your study could contribute toward filling that gap by taking a different approach. For example, taking a qualitative approach to a research area that is typically approached quantitatively. Of course, if you’re going to go against the methodological grain, you’ll need to provide a strong justification for why your proposed approach makes sense. Nevertheless, it is something worth at least considering.

Regardless of which route you opt for, you need to pay careful attention to the methodologies used in the relevant studies and provide at least some discussion about this in your write-up. Again, it’s useful to keep track of this on some sort of spreadsheet or catalogue as you digest each article, so consider grabbing a copy of our free literature catalogue if you don’t have anything in place.

Bringing It All Together

Alright, so we’ve looked at five important questions that you need to ask (and answer) to help you develop a strong synthesis within your literature review.  To recap, these are:

• Which things are broadly agreed upon within the current research?
• Which things are the subject of disagreement (or at least, present mixed findings)?
• Which theories seem to be central to your research topic and how do they relate or compare to each other?
• Which contexts have (and haven’t) been covered?
• Which methodological approaches are most common?

Importantly, you’re not just asking yourself these questions for the sake of asking them – they’re not just a reflection exercise. You need to weave your answers to them into your actual literature review when you write it up. How exactly you do this will vary from project to project depending on the structure you opt for, but you’ll still need to address them within your literature review, whichever route you go.

The best approach is to spend some time actually writing out your answers to these questions, as opposed to just thinking about them in your head. Putting your thoughts onto paper really helps you flesh out your thinking . As you do this, don’t just write down the answers – instead, think about what they mean in terms of the research gap you’ll present , as well as the methodological approach you’ll take . Your literature synthesis needs to lay the groundwork for these two things, so it’s essential that you link all of it together in your mind, and of course, on paper.

Psst… there’s more!

This post is an extract from our bestselling short course, Literature Review Bootcamp . If you want to work smart, you don't want to miss this .

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The Sheridan Libraries

• Write a Literature Review
• Sheridan Libraries
• Find This link opens in a new window
• Evaluate This link opens in a new window

Get Organized

• Lit Review Prep Use this template to help you evaluate your sources, create article summaries for an annotated bibliography, and a synthesis matrix for your lit review outline.

Synthesize your Information

Synthesize: combine separate elements to form a whole.

Synthesis Matrix

A synthesis matrix helps you record the main points of each source and document how sources relate to each other.

After summarizing and evaluating your sources, arrange them in a matrix or use a citation manager to help you see how they relate to each other and apply to each of your themes or variables.  

By arranging your sources by theme or variable, you can see how your sources relate to each other, and can start thinking about how you weave them together to create a narrative.

• Step-by-Step Approach
• Example Matrix from NSCU
• Matrix Template
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• Last Updated: Sep 26, 2023 10:25 AM
• URL: https://guides.library.jhu.edu/lit-review

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How to Write a Literature Review

• 6. Synthesize
• Literature Reviews: A Recap
• Reading Journal Articles
• Does it Describe a Literature Review?
• 1. Identify the Question
• 2. Review Discipline Styles
• Searching Article Databases
• Finding Full-Text of an Article
• Citation Chaining
• When to Stop Searching
• 4. Manage Your References
• 5. Critically Analyze and Evaluate

Synthesis Visualization

Synthesis matrix example.

• 7. Write a Literature Review

• Synthesis Worksheet

About Synthesis

Approaches to synthesis.

You can sort the literature in various ways, for example:

How to Begin?

Read your sources carefully and find the main idea(s) of each source

Look for similarities in your sources – which sources are talking about the same main ideas? (for example, sources that discuss the historical background on your topic)

Use the worksheet (above) or synthesis matrix (below) to get organized

This work can be messy. Don't worry if you have to go through a few iterations of the worksheet or matrix as you work on your lit review!

Four Examples of Student Writing

In the four examples below, only ONE shows a good example of synthesis: the fourth column, or  Student D . For a web accessible version, click the link below the image.

Long description of "Four Examples of Student Writing" for web accessibility

• Download a copy of the "Four Examples of Student Writing" chart

Click on the example to view the pdf.

From Jennifer Lim

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Literature Review Basics

• What is a Literature Review?
• Synthesizing Research
• Using Research & Synthesis Tables
• Additional Resources

Synthesis: What is it?

First, let's be perfectly clear about what synthesizing your research isn't :

• - It isn't  just summarizing the material you read
• - It isn't  generating a collection of annotations or comments (like an annotated bibliography)
• - It isn't  compiling a report on every single thing ever written in relation to your topic

When you  synthesize  your research, your job is to help your reader understand the current state of the conversation on your topic, relative to your research question.  That may include doing the following:

• - Selecting and using representative work on the topic
• - Identifying and discussing trends in published data or results
• - Identifying and explaining the impact of common features (study populations, interventions, etc.) that appear frequently in the literature
• - Explaining controversies, disputes, or central issues in the literature that are relevant to your research question
• - Identifying gaps in the literature, where more research is needed
• - Establishing the discussion to which your own research contributes and demonstrating the value of your contribution

Essentially, you're telling your reader where they are (and where you are) in the scholarly conversation about your project.

Synthesis: How do I do it?

Synthesis, step by step.

This is what you need to do  before  you write your review.

• Identify and clearly describe your research question (you may find the Formulating PICOT Questions table at  the Additional Resources tab helpful).
• Collect sources relevant to your research question.
• Organize and describe the sources you've found -- your job is to identify what  types  of sources you've collected (reviews, clinical trials, etc.), identify their  purpose  (what are they measuring, testing, or trying to discover?), determine the  level of evidence  they represent (see the Levels of Evidence table at the Additional Resources tab ), and briefly explain their  major findings . Use a Research Table to document this step.
• Study the information you've put in your Research Table and examine your collected sources, looking for  similarities  and  differences . Pay particular attention to  populations ,   methods  (especially relative to levels of evidence), and  findings .
• Analyze what you learn in (4) using a tool like a Synthesis Table. Your goal is to identify relevant themes, trends, gaps, and issues in the research.  Your literature review will collect the results of this analysis and explain them in relation to your research question.

Analysis tips

• - Sometimes, what you  don't  find in the literature is as important as what you do find -- look for questions that the existing research hasn't answered yet.
• - If any of the sources you've collected refer to or respond to each other, keep an eye on how they're related -- it may provide a clue as to whether or not study results have been successfully replicated.
• - Sorting your collected sources by level of evidence can provide valuable insight into how a particular topic has been covered, and it may help you to identify gaps worth addressing in your own work.
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How to Write a Literature Review - A Self-Guided Tutorial

• Literature Reviews: A Recap
• Reading Journal Articles
• Does it describe a Literature Review?
• 1. Identify the question
• 2. Review discipline styles
• Searching article databases - video
• Finding the article full-text
• Citation trails
• When to stop searching
• Citation Managers
• 5. Critically analyze and evaluate
• 6. Synthesize
• 7. Write literature review
• Additional Resources

You can meet with a librarian to talk about your literature review, or other library-related topics.

You can sort the literature in various ways, for example:

Synthesis Vizualization

Four examples of student writing.

In the four examples below, only ONE shows a good example of synthesis: the fourth column, or  Student D . For a web accessible version, click the link below the image.

Long description of "Four Examples of Student Writing" for web accessibility

• Download a copy of the "Four Examples of Student Writing" chart

Synthesis Matrix Example

From Jennifer Lim

Synthesis Templates

Synthesis grids are organizational tools used to record the main concepts of your sources and can help you make connections about how your sources relate to one another.

• Source Template Basic Literature Review Source Template from Walden University Writing Center to help record the main findings and concepts from different articles.
• Sample Literature Review Grids This spreadsheet contains multiple tabs with different grid templates. Download or create your own copy to begin recording notes.
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Literature Review How To

• Things To Consider
• Synthesizing Sources
• Video Tutorials
• Books On Literature Reviews

What is Synthesis

What is Synthesis? Synthesis writing is a form of analysis related to comparison and contrast, classification and division. On a basic level, synthesis requires the writer to pull together two or more summaries, looking for themes in each text. In synthesis, you search for the links between various materials in order to make your point. Most advanced academic writing, including literature reviews, relies heavily on synthesis. (Temple University Writing Center)  

How To Synthesize Sources in a Literature Review

Literature reviews synthesize large amounts of information and present it in a coherent, organized fashion. In a literature review you will be combining material from several texts to create a new text – your literature review.

You will use common points among the sources you have gathered to help you synthesize the material. This will help ensure that your literature review is organized by subtopic, not by source. This means various authors' names can appear and reappear throughout the literature review, and each paragraph will mention several different authors. 

When you shift from writing summaries of the content of a source to synthesizing content from sources, there is a number things you must keep in mind: 

• Look for specific connections and or links between your sources and how those relate to your thesis or question.
• When writing and organizing your literature review be aware that your readers need to understand how and why the information from the different sources overlap.
• Organize your literature review by the themes you find within your sources or themes you have identified. 
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Literature reviews: synthesis.

• Criticality

Synthesise Information

So, how can you create paragraphs within your literature review that demonstrates your knowledge of the scholarship that has been done in your field of study?  

You will need to present a synthesis of the texts you read.  

Doug Specht, Senior Lecturer at the Westminster School of Media and Communication, explains synthesis for us in the following video:  

Synthesising Texts  

What is synthesis? 

Synthesis is an important element of academic writing, demonstrating comprehension, analysis, evaluation and original creation.  

With synthesis you extract content from different sources to create an original text. While paraphrase and summary maintain the structure of the given source(s), with synthesis you create a new structure.  

The sources will provide different perspectives and evidence on a topic. They will be put together when agreeing, contrasted when disagreeing. The sources must be referenced.  

Perfect your synthesis by showing the flow of your reasoning, expressing critical evaluation of the sources and drawing conclusions.  

When you synthesise think of "using strategic thinking to resolve a problem requiring the integration of diverse pieces of information around a structuring theme" (Mateos and Sole 2009, p448). 

Synthesis is a complex activity, which requires a high degree of comprehension and active engagement with the subject. As you progress in higher education, so increase the expectations on your abilities to synthesise. 

How to synthesise in a literature review: 

Identify themes/issues you'd like to discuss in the literature review. Think of an outline.  

Read the literature and identify these themes/issues.  

Critically analyse the texts asking: how does the text I'm reading relate to the other texts I've read on the same topic? Is it in agreement? Does it differ in its perspective? Is it stronger or weaker? How does it differ (could be scope, methods, year of publication etc.). Draw your conclusions on the state of the literature on the topic.  

Start writing your literature review, structuring it according to the outline you planned.  

Put together sources stating the same point; contrast sources presenting counter-arguments or different points.  

Present your critical analysis.  

Always provide the references. 

The best synthesis requires a "recursive process" whereby you read the source texts, identify relevant parts, take notes, produce drafts, re-read the source texts, revise your text, re-write... (Mateos and Sole, 2009). 

What is good synthesis?  

The quality of your synthesis can be assessed considering the following (Mateos and Sole, 2009, p439):  

Integration and connection of the information from the source texts around a structuring theme. 

Selection of ideas necessary for producing the synthesis. 

Appropriateness of the interpretation.  

Elaboration of the content.  

Example of Synthesis

Original texts (fictitious): 

Synthesis: 

Animal experimentation is a subject of heated debate. Some argue that painful experiments should be banned. Indeed it has been demonstrated that such experiments make animals suffer physically and psychologically (Chowdhury 2012; Panatta and Hudson 2016). On the other hand, it has been argued that animal experimentation can save human lives and reduce harm on humans (Smith 2008). This argument is only valid for toxicological testing, not for tests that, for example, merely improve the efficacy of a cosmetic (Turner 2015). It can be suggested that animal experimentation should be regulated to only allow toxicological risk assessment, and the suffering to the animals should be minimised.   

Bibliography

Mateos, M. and Sole, I. (2009). Synthesising Information from various texts: A Study of Procedures and Products at Different Educational Levels. European Journal of Psychology of Education,  24 (4), 435-451. Available from https://doi.org/10.1007/BF03178760 [Accessed 29 June 2021].

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Systematic reviews & evidence synthesis methods.

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• What is Evidence Synthesis?
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• 0. Preliminary Searching
• 1. Develop a Protocol
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• 4. Select Grey Literature Sources
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About This Guide

This research guide provides an overview of the evidence synthesis process, guidance documents for conducting evidence synthesis projects, and links to resources to help you conduct a comprehensive and systematic search of the scholarly literature. Navigate the guide using the tabs on the left.

"Evidence synthesis" refers to rigorous, well-documented methods of identifying, selecting, and combining results from multiple studies. These projects are conducted by teams and follow specific methodologies to minimize bias and maximize reproducibility. A systematic review is a type of evidence synthesis. We use the term evidence synthesis to better reflect the breadth of methodologies that we support, including systematic reviews, scoping reviews , evidence gap maps, umbrella reviews, meta-analyses and others.

Note: Librarians at UC Irvine Libraries have supported systematic reviews and related methodologies in STEM fields for several years. As our service has evolved, we have added capacity to support these reviews in the Social Sciences as well.

Systematic Review OR Literature Review Conducted Systematically?

There are many types of literature reviews. Before beginning a systematic review, consider whether it is the best type of review for your question, goals, and resources. The table below compares systematic reviews, scoping reviews, and systematized reviews (narrative literature reviews employing some, but not all elements of a systematic review) to help you decide which is best for you. See the Types of Evidence Synthesis page for a more in-depth overview at types of reviews.

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Writing a Literature Review: Organize, Synthesize, Evaluate

• Literature Review Process
• Literature Search
• Record your Search
• Organize, Synthesize, Evaluate
• Getting help

Table of Contents

On this page you will find:

Organizing Literature and Notes

How to scan an article.

• Reading for Comprehension
• Synthesis Matrix Information

Steps to take in organizing your literature and notes:

• Find common themes and organize the works into categories.
• Develop a subject level outline with studies you’ve found
• Expand or limit your search based on the information you found.
• How the works in each category relate to each other
• How the categories relate to each other and to your overall theme.

Available tools:

• Synthesis Matrix The "synthesis matrix" is an approach to organizing, monitoring, and documenting your search activities.
• Concept Mapping Concept Maps are graphic representations of topics, ideas, and their relationships. They allow users to group information in related modules so that the connections between and among the modules become more readily apparent than they might from an examination of a list. It can be done on paper or using specific software.
• Mind Mapping A mind map is a visual representation of hierarchical information that includes a central idea surrounded by connected branches of associated topics.
• NVIVO NVIVO is a qualitative data analysis software that can be applied for engineering literature review.

Synthesis Matrix

• Writing A Literature Review and Using a Synthesis Matrix Writing Center, Florida International University
• The Matrix Method of Literature Reviews Article from Health Promotion Practice journal.

Sample synthesis matrix

Synthesis matrix video

Skim the article to get the “big picture” for relevancy to your topic. You don’t have to understand every single idea in a text the first time you read it.

• Where was the paper published?
• What kind of journal it is? Is the journal peer-reviewed?
• Can you tell what the paper is about?
• Where are they from?
• What are the sections of the article?
• Are these clearly defined?  
• Can you figure out the purpose of the study, methodology, results and conclusion?
• Mentally review what you know about the topic
• Do you know enough to be able to understand the paper? If not, first read about the unfamiliar concepts  
• What is the overall context?
• Is the problem clearly stated?
• What does the paper bring new?
• Did it miss any previous major studies?
• Identify all the author’s assumptions.  
• Analyze the visuals for yourself and try to understand each of them. Make notes on what you understand. Write questions of what you do not understand. Make a guess about what materials/methods you expect to see. Do your own data interpretation and check them against the conclusions.  
• Do you agree with the author’s opinion?
• As you read, write down terms, techniques, unfamiliar concepts and look them up  
• Save retrieved sources to a reference manager

Read for Comprehension and Take Notes

Read for comprehension

• After first evaluation of sources, critically read the selected sources. Your goal is to determine how much of it to accept, determine its value, and decide whether you plan to include it in your literature review.
• Read the whole article, section by section but not necessarily in order and make sure you understand:

Introduction : What is known about the research and what is still unknown. Methods : What was measured? How was measured? Were the measurement appropriate? Did they offer sufficient evidence? Results : What is the main finding? Were there enough data presented? Were there problems not addressed? Discussions : Are these conclusions appropriate? Are there other factors that might have influenced? What does it need to be done to answer remaining questions?

• Find answers to your question from first step
• Formulate new questions and try to answer them
• Can you find any discrepancies? What would you have done differently?
• Re-read the whole article or just sections as many times you feel you need to
• When you believe that you have understood the article, write a summary in your own words (Make sure that there is nothing left that you cannot understand)

As you read, take (extensive) notes. Create your own system to take notes but be consistent. Remember that notes can be taken within the citation management tool.

What to write in your notes:

• identify key topic, methodology, key terms
• identify emphases, strengths, weaknesses, gaps (if any)
• determine relationships to other studies
• identify the relationship to your research topic
• new questions you have  
• suggestions for new directions, new sources to read
• everything else that seems relevant
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Literature Synthesis

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Cite this chapter

• Ana Paula Cardoso Ermel   ORCID: orcid.org/0000-0002-3874-9792 5 ,
• D. P. Lacerda   ORCID: orcid.org/0000-0002-8011-3376 6 ,
• Maria Isabel W. M. Morandi   ORCID: orcid.org/0000-0003-1337-1487 7 &
• Leandro Gauss   ORCID: orcid.org/0000-0001-5708-5912 8  

1 Citations

• The original version of this chapter was revised: Figure 5.1 was moved to section 5.2.9. The correction to this chapter can be found at https://doi.org/10.1007/978-3-030-75722-9_10

This chapter addresses the concept of Literature Synthesis and classifies it as Configurative and Aggregative based upon the research approach and objectives. For each type of synthesis, its main characteristics, techniques, and applications are pointed out.

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Change history

06 february 2022.

In addition to the changes described above, we note that

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Cardoso Ermel, A.P., Lacerda, D.P., Morandi, M.I.W.M., Gauss, L. (2021). Literature Synthesis. In: Literature Reviews. Springer, Cham. https://doi.org/10.1007/978-3-030-75722-9_5

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Synthetic literature reviews: An introduction

By Steve Wallis and Bernadette Wright 26/05/2020

Whether you are writing a funding proposal or an academic paper, you will most likely be required to start with a literature review of some kind. Despite (or because of) the work involved, a literature review is a great opportunity to showcase your knowledge on a topic. In this post, we’re going to take it one step further. We’re going to tell you a very practical approach to conducting literature reviews that allows you to show that you are advancing scientific knowledge before your project even begins. Also – and this is no small bonus – this approach lets you show how your literature review will lead to a more successful project.

Literature review – start with the basics

A literature review helps you shape effective solutions to the problems you (and your organisation) are facing. A literature review also helps you demonstrate the value of your activities. You can show how much you add to the process before you spend any money collecting new data. Finally, your literature review helps you avoid reinventing the wheel by showing you what relevant research already exists, so that you can target your new research more efficiently and more effectively.

We all want to conduct good research and have a meaningful impact on people’s lives. To do this, a literature review is a critical step. For funders, a literature review is especially important because it shows how much useful knowledge the writer already has.

Past methods of literature reviews tend to be focused on ‘muscle power’, that is spending more time and more effort to review more papers and adhering more closely to accepted standards. Examples of standards for conducting literature reviews include the PRISMA Statement for Reporting Systematic Reviews and Meta-Analyses of Studies That Evaluate Health Care Interventions and the guidelines for assessing the quality and applicability of systematic reviews developed by the Task Force on Systematic Review and Guidelines . Given the untold millions of papers in many disciplines, even a large literature review that adheres to the best guidelines does little to move us toward integrated knowledge in and across disciplines.

In short, we need we need to work smarter, not harder!

Synthetic literature reviews

One approach that can provide more benefit is the synthetic literature review. Synthetic meaning synthesised or integrated, not artificial. Rather than explaining and reflecting on the results of previous studies (as is typically done in literature reviews), a synthetic literature review strives to create a new and more useful theoretical perspective by rigorously integrating the results of previous studies.

Many people find the process of synthesis difficult, elusive, or mysterious. When presenting their views and making recommendations for research, they tend to fall back on intuition (which is neither harder nor smarter).

After defining your research topic (‘poverty’ for example), the next step is to search the literature for existing theories or models of poverty that have been developed from research. You can use Google Scholar or your institutional database, or the assistance of a research librarian. A broad topic such as ‘poverty’, however, will lead you to millions of articles. You’ll narrow that field by focusing more closely on your topic and adding search terms. For example, you might be more interested in poverty among Latino communities in central California. You might also focus your search according to the date of the study (often, but not always, more recent results are preferred), or by geographic location. Continue refining and focusing your search until you have a workable number of papers (depending on your available time and resources). You might also take this time to throw out the papers that seem to be less relevant.

Skim those papers to be sure that they are really relevant to your topic. Once you have chosen a workable number of relevant papers, it is time to start integrating them.

Next, sort them according to the quality of their data.

Next, read the theory presented in each paper and create a diagram of the theory. The theory may be found in a section called ‘theory’ or sometimes in the ‘introduction’. For research papers, that presented theory may have changed during the research process, so you should look for the theory in the ‘findings’, ‘results’, or ‘discussion’ sections.

That diagram should include all relevant concepts from the theory and show the causal connections between the concepts that have been supported by research (some papers will present two theories, one before and one after the research – use the second one – only the hypotheses that have been supported by the research).

For a couple of brief and partial example from a recent interdisciplinary research paper, one theory of poverty might say ‘Having more education will help people to stay out of poverty’, while another might say ‘The more that the economy develops, the less poverty there will be’.

We then use those statements to create a diagram as we have in Figure 1.

Figure 1. Two (simple, partial) theories of poverty. (We like to use dashed lines to indicate ’causes less’, and solid lines to indicate ’causes more’)

When you have completed a diagram for each theory, the next step is to synthesise (integrate) them where the concepts are the same (or substantively similar) between two or more theories. With causal diagrams such as these, the process of synthesis becomes pretty direct. We simply combine the two (or more) theories to create a synthesised theory, such as in Figure 2.

Figure 2. Two theories synthesised where they overlap (in this case theories of poverty)

Much like a road map, a causal diagram of a theory with more concepts and more connecting arrows is more useful for navigation. You can show that your literature review is better than previous reviews by showing that you have taken a number of fragmented theories (as in Figure 1) and synthesised them to create a more coherent theory (as in Figure 2).

To go a step further, you may use Integrative Propositional Analysis (IPA) to quantify the extent to which your research has improved the structure and potential usefulness of your knowledge through the synthesis. Another source is our new book from Practical Mapping for Applied Research and Program Evaluation (see especially Chapter 5). (For the basics, you can look at Chapter One for free on the publisher’s site by clicking on the ‘Preview’ tab here. )

Once you become comfortable with the process, you will certainly be working ‘smarter’ and showcasing your knowledge to funders!

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How to Synthesize Written Information from Multiple Sources

Shona McCombes

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B.A., English Literature, University of Glasgow

Shona McCombes is the content manager at Scribbr, Netherlands.

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When you write a literature review or essay, you have to go beyond just summarizing the articles you’ve read – you need to synthesize the literature to show how it all fits together (and how your own research fits in).

Synthesizing simply means combining. Instead of summarizing the main points of each source in turn, you put together the ideas and findings of multiple sources in order to make an overall point.

At the most basic level, this involves looking for similarities and differences between your sources. Your synthesis should show the reader where the sources overlap and where they diverge.

Unsynthesized Example

Franz (2008) studied undergraduate online students. He looked at 17 females and 18 males and found that none of them liked APA. According to Franz, the evidence suggested that all students are reluctant to learn citations style. Perez (2010) also studies undergraduate students. She looked at 42 females and 50 males and found that males were significantly more inclined to use citation software ( p < .05). Findings suggest that females might graduate sooner. Goldstein (2012) looked at British undergraduates. Among a sample of 50, all females, all confident in their abilities to cite and were eager to write their dissertations.

Synthesized Example

Studies of undergraduate students reveal conflicting conclusions regarding relationships between advanced scholarly study and citation efficacy. Although Franz (2008) found that no participants enjoyed learning citation style, Goldstein (2012) determined in a larger study that all participants watched felt comfortable citing sources, suggesting that variables among participant and control group populations must be examined more closely. Although Perez (2010) expanded on Franz’s original study with a larger, more diverse sample…

Step 1: Organize your sources

After collecting the relevant literature, you’ve got a lot of information to work through, and no clear idea of how it all fits together.

Before you can start writing, you need to organize your notes in a way that allows you to see the relationships between sources.

One way to begin synthesizing the literature is to put your notes into a table. Depending on your topic and the type of literature you’re dealing with, there are a couple of different ways you can organize this.

Summary table

A summary table collates the key points of each source under consistent headings. This is a good approach if your sources tend to have a similar structure – for instance, if they’re all empirical papers.

Each row in the table lists one source, and each column identifies a specific part of the source. You can decide which headings to include based on what’s most relevant to the literature you’re dealing with.

For example, you might include columns for things like aims, methods, variables, population, sample size, and conclusion.

For each study, you briefly summarize each of these aspects. You can also include columns for your own evaluation and analysis.

The summary table gives you a quick overview of the key points of each source. This allows you to group sources by relevant similarities, as well as noticing important differences or contradictions in their findings.

Synthesis matrix

A synthesis matrix is useful when your sources are more varied in their purpose and structure – for example, when you’re dealing with books and essays making various different arguments about a topic.

Each column in the table lists one source. Each row is labeled with a specific concept, topic or theme that recurs across all or most of the sources.

Then, for each source, you summarize the main points or arguments related to the theme.

The purposes of the table is to identify the common points that connect the sources, as well as identifying points where they diverge or disagree.

Step 2: Outline your structure

Now you should have a clear overview of the main connections and differences between the sources you’ve read. Next, you need to decide how you’ll group them together and the order in which you’ll discuss them.

For shorter papers, your outline can just identify the focus of each paragraph; for longer papers, you might want to divide it into sections with headings.

There are a few different approaches you can take to help you structure your synthesis.

If your sources cover a broad time period, and you found patterns in how researchers approached the topic over time, you can organize your discussion chronologically .

That doesn’t mean you just summarize each paper in chronological order; instead, you should group articles into time periods and identify what they have in common, as well as signalling important turning points or developments in the literature.

If the literature covers various different topics, you can organize it thematically .

That means that each paragraph or section focuses on a specific theme and explains how that theme is approached in the literature.

Source Used with Permission: The Chicago School

If you’re drawing on literature from various different fields or they use a wide variety of research methods, you can organize your sources methodologically .

That means grouping together studies based on the type of research they did and discussing the findings that emerged from each method.

If your topic involves a debate between different schools of thought, you can organize it theoretically .

That means comparing the different theories that have been developed and grouping together papers based on the position or perspective they take on the topic, as well as evaluating which arguments are most convincing.

Step 3: Write paragraphs with topic sentences

What sets a synthesis apart from a summary is that it combines various sources. The easiest way to think about this is that each paragraph should discuss a few different sources, and you should be able to condense the overall point of the paragraph into one sentence.

This is called a topic sentence , and it usually appears at the start of the paragraph. The topic sentence signals what the whole paragraph is about; every sentence in the paragraph should be clearly related to it.

A topic sentence can be a simple summary of the paragraph’s content:

“Early research on [x] focused heavily on [y].”

For an effective synthesis, you can use topic sentences to link back to the previous paragraph, highlighting a point of debate or critique:

“Several scholars have pointed out the flaws in this approach.” “While recent research has attempted to address the problem, many of these studies have methodological flaws that limit their validity.”

By using topic sentences, you can ensure that your paragraphs are coherent and clearly show the connections between the articles you are discussing.

As you write your paragraphs, avoid quoting directly from sources: use your own words to explain the commonalities and differences that you found in the literature.

Don’t try to cover every single point from every single source – the key to synthesizing is to extract the most important and relevant information and combine it to give your reader an overall picture of the state of knowledge on your topic.

Step 4: Revise, edit and proofread

Like any other piece of academic writing, synthesizing literature doesn’t happen all in one go – it involves redrafting, revising, editing and proofreading your work.

Checklist for Synthesis

•   Do I introduce the paragraph with a clear, focused topic sentence?
•   Do I discuss more than one source in the paragraph?
•   Do I mention only the most relevant findings, rather than describing every part of the studies?
•   Do I discuss the similarities or differences between the sources, rather than summarizing each source in turn?
•   Do I put the findings or arguments of the sources in my own words?
•   Is the paragraph organized around a single idea?
•   Is the paragraph directly relevant to my research question or topic?
•   Is there a logical transition from this paragraph to the next one?

Further Information

How to Synthesise: a Step-by-Step Approach

Help…I”ve Been Asked to Synthesize!

Learn how to Synthesise (combine information from sources)

How to write a Psychology Essay

Related Articles

Student Resources

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How to Write an Abstract APA Format

APA References Page Formatting and Example

APA Title Page (Cover Page) Format, Example, & Templates

How do I Cite a Source with Multiple Authors in APA Style?

How to Write a Psychology Essay

Want to create or adapt books like this? Learn more about how Pressbooks supports open publishing practices.

Chapter 7: Synthesizing Sources

Learning objectives.

At the conclusion of this chapter, you will be able to:

• synthesize key sources connecting them with the research question and topic area.

7.1 Overview of synthesizing

7.1.1 putting the pieces together.

Combining separate elements into a whole is the dictionary definition of synthesis.  It is a way to make connections among and between numerous and varied source materials.  A literature review is not an annotated bibliography, organized by title, author, or date of publication.  Rather, it is grouped by topic to create a whole view of the literature relevant to your research question.

Your synthesis must demonstrate a critical analysis of the papers you collected as well as your ability to integrate the results of your analysis into your own literature review.  Each paper collected should be critically evaluated and weighed for “adequacy, appropriateness, and thoroughness” ( Garrard, 2017 ) before inclusion in your own review.  Papers that do not meet this criteria likely should not be included in your literature review.

Begin the synthesis process by creating a grid, table, or an outline where you will summarize, using common themes you have identified and the sources you have found. The summary grid or outline will help you compare and contrast the themes so you can see the relationships among them as well as areas where you may need to do more searching. Whichever method you choose, this type of organization will help you to both understand the information you find and structure the writing of your review.  Remember, although “the means of summarizing can vary, the key at this point is to make sure you understand what you’ve found and how it relates to your topic and research question” ( Bennard et al., 2014 ).

As you read through the material you gather, look for common themes as they may provide the structure for your literature review.  And, remember, research is an iterative process: it is not unusual to go back and search information sources for more material.

At one extreme, if you are claiming, ‘There are no prior publications on this topic,’ it is more likely that you have not found them yet and may need to broaden your search.  At another extreme, writing a complete literature review can be difficult with a well-trod topic.  Do not cite it all; instead cite what is most relevant.  If that still leaves too much to include, be sure to reference influential sources…as well as high-quality work that clearly connects to the points you make. ( Klingner, Scanlon, & Pressley, 2005 ).

7.2 Creating a summary table

Literature reviews can be organized sequentially or by topic, theme, method, results, theory, or argument.  It’s important to develop categories that are meaningful and relevant to your research question.  Take detailed notes on each article and use a consistent format for capturing all the information each article provides.  These notes and the summary table can be done manually, using note cards.  However, given the amount of information you will be recording, an electronic file created in a word processing or spreadsheet is more manageable. Examples of fields you may want to capture in your notes include:

• Authors’ names
• Article title
• Publication year
• Main purpose of the article
• Methodology or research design
• Participants
• Measurement
• Conclusions

  Other fields that will be useful when you begin to synthesize the sum total of your research:

• Specific details of the article or research that are especially relevant to your study
• Key terms and definitions
• Strengths or weaknesses in research design
• Relationships to other studies
• Possible gaps in the research or literature (for example, many research articles conclude with the statement “more research is needed in this area”)
• Finally, note how closely each article relates to your topic.  You may want to rank these as high, medium, or low relevance.  For papers that you decide not to include, you may want to note your reasoning for exclusion, such as ‘small sample size’, ‘local case study,’ or ‘lacks evidence to support assertion.’

This short video demonstrates how a nursing researcher might create a summary table.

7.2.1 Creating a Summary Table

  Summary tables can be organized by author or by theme, for example:

For a summary table template, see http://blogs.monm.edu/writingatmc/files/2013/04/Synthesis-Matrix-Template.pdf

7.3 Creating a summary outline

An alternate way to organize your articles for synthesis it to create an outline. After you have collected the articles you intend to use (and have put aside the ones you won’t be using), it’s time to identify the conclusions that can be drawn from the articles as a group.

  Based on your review of the collected articles, group them by categories.  You may wish to further organize them by topic and then chronologically or alphabetically by author.  For each topic or subtopic you identified during your critical analysis of the paper, determine what those papers have in common.  Likewise, determine which ones in the group differ.  If there are contradictory findings, you may be able to identify methodological or theoretical differences that could account for the contradiction (for example, differences in population demographics).  Determine what general conclusions you can report about the topic or subtopic as the entire group of studies relate to it.  For example, you may have several studies that agree on outcome, such as ‘hands on learning is best for science in elementary school’ or that ‘continuing education is the best method for updating nursing certification.’ In that case, you may want to organize by methodology used in the studies rather than by outcome.

Organize your outline in a logical order and prepare to write the first draft of your literature review.  That order might be from broad to more specific, or it may be sequential or chronological, going from foundational literature to more current.  Remember, “an effective literature review need not denote the entire historical record, but rather establish the raison d’etre for the current study and in doing so cite that literature distinctly pertinent for theoretical, methodological, or empirical reasons.” ( Milardo, 2015, p. 22 ).

As you organize the summarized documents into a logical structure, you are also appraising and synthesizing complex information from multiple sources.  Your literature review is the result of your research that synthesizes new and old information and creates new knowledge.

7.4 Additional resources:

Literature Reviews: Using a Matrix to Organize Research / Saint Mary’s University of Minnesota

Literature Review: Synthesizing Multiple Sources / Indiana University

Writing a Literature Review and Using a Synthesis Matrix / Florida International University

 Sample Literature Reviews Grid / Complied by Lindsay Roberts

Select three or four articles on a single topic of interest to you. Then enter them into an outline or table in the categories you feel are important to a research question. Try both the grid and the outline if you can to see which suits you better. The attached grid contains the fields suggested in the video .

Literature Review Table  

Test yourself.

• Select two articles from your own summary table or outline and write a paragraph explaining how and why the sources relate to each other and your review of the literature.
• In your literature review, under what topic or subtopic will you place the paragraph you just wrote?

Image attribution

Literature Reviews for Education and Nursing Graduate Students Copyright © by Linda Frederiksen is licensed under a Creative Commons Attribution 4.0 International License , except where otherwise noted.

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Synthesis and Literature Reviews

Why do we seek to understand the ways that authors or sources “converse” with one another?

So that we can synthesize various perspectives on a topic to more deeply understand it .

In academic writing, this understanding of the “conversation” may become the content of an explanatory synthesis paper – a paper in which you, the writer, point out various various themes or key points from a conversation on a particular topic.

Or, another assignment that you may complete in college is a literature review , which applies your synthesis skills. Literature reviews are often found in the beginning of scholarly journal articles. Literature reviews synthesize previous research that has been done on a particular topic, summarizing important works in the history of research on that topic.

• Literature reviews can be arranged by topic or theme , much like a traditional explanatory synthesis paper.
• Literature reviews can also be arranged chronologically , according to various time periods of research on a topic (i.e., what was published ten years ago, five years ago, and within the last year, for example).
• Finally, literature reviews can be arranged by discipline or field (i.e., what is the current research being done by biologists on this topic? What is the current research being done by psychologists on this topic? What is the current research being done by [insert academic discipline] on this topic?).

Just like in an explanatory synthesis paper, a Literature Review offers  only  a report on what others have already written about. The Literature Review does not reflect the author’s own argument or contributions to the field of research. Instead, it indicates that the author has read others’ important contributions and understands what has come before him or her.

The Literature Review provides context for the author’s own new research. It is the basis and background out of which the author’s research grows. Context = credibility in academic writing. When authors have broad Literature Review, they demonstrate their credibility as researchers.

English 102: Reading, Research, and Writing by Emilie Zickel is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License , except where otherwise noted.

Chaos to Clarity: Structuring Your Literature Review Format

Master literature review format! Learn key sections, effective citation & analysis tips to write a strong academic review.

Ever wondered how to dive into a mountain of books and articles and come up with something that not just makes sense but shines new light on a topic? What if there was a way to neatly tie together all that information, spot what’s missing, and maybe even pave the way for discoveries? 

That’s what you are going to learn in this article, literature reviews—a place where chaos meets order, and where your insights could set the stage for the next big thing. Let’s break down the literature review format , your essential guide to properly writing a literature review.

Dissecting Literature Review Format 

There are 6 main sections to make a note of while writing a literature review. Those are:

The Introduction Section

Topic background, conceptual framework.

• Synthesis and Evaluation in Literature Reviews
• Conclusion for Your Literature Review
• Reference List in Your Literature Review

Also Read: Essential Components of a Literature Review

The introduction of your literature review is where you set the stage for the entire document. It’s your first opportunity to engage your readers and provide a clear blueprint of what your review will cover and why it matters. This section does more than merely introduce the topic; it establishes the context, defines the scope, and outlines the purpose and objectives of your literature review.

Things to keep in mind while writing an introduction:

• Craft a compelling opening
• Establish the Context and Justification
• Define the Scope and Objectives
• Lay out the Structure
• Give an overview of the Structure

The “Topic Background” section of a literature review serves as the cornerstone for understanding the evolution and current state of the subject matter. It is divided into two crucial sub-sections: Historical Context and Current State of the Topic . 

Delving into these areas provides you with a comprehensive backdrop against which the literature review is framed, enriching the reader’s understanding of why the topic is of interest and what has influenced its development to the current state.

Historical Context

The Historical Context is fundamental in setting the stage for the entire literature review. This section is not just a chronology of events or developments; it’s a curated narrative that highlights the key milestones and turning points that have significantly impacted the topic. 

By examining the historical evolution, the review establishes a timeline of how understanding and perspectives have shifted over the years.

Summary Of Key Historical Developments

This involves identifying and summarizing the major breakthroughs, shifts in thinking, or seminal works that have shaped the topic. It’s important to focus on developments that have a direct relevance to the current understanding and state of the subject. For example, if the topic is about the evolution of renewable energy technologies, this part would outline the initial discovery and use of renewable sources, significant technological innovations, and pivotal policy decisions that have influenced the field.

Relevance Of Historical Context To The Topic

After outlining the key historical developments, it’s crucial to connect these events to the present topic. This means discussing how past events have laid the groundwork for current theories, practices, or debates within the field. It involves analyzing the impact of historical milestones on the subject matter, and explaining how they have contributed to current knowledge, challenges, and research questions. This section makes it clear why understanding history is essential for anyone researching or studying the topic today.

Current State Of The Topic

Moving from the historical context, the review transitions to the present with the Current State of the Topic. This part assesses the latest research, trends, debates, and technological advancements that define the subject area at the moment.

Current Trends Or Updates

Here, the focus shifts to what is happening in the field right now. This could include recent research findings, emerging theories, new methodologies, or the latest technological innovations. The aim is to provide a snapshot of the current research landscape, identifying what themes, questions, or problems are being actively explored. For instance, in the context of digital marketing, this might involve discussing the rise of artificial intelligence in customer relationship management or the impact of social media trends on marketing strategies.

Impact Of These Trends On The Subject Matter

The final step is to assess the implications of these current trends for the topic. This includes considering how recent developments have advanced the field, the challenges they present, and the opportunities they open up for future research. It’s about connecting the dots between what’s happening now and what it means for the subject area moving forward. This not only helps to frame the research questions that the literature review will address but also sets the stage for identifying gaps in the current knowledge, thereby guiding the direction of future studies.

Also Read: What is a literature review? Get the concept and start using it

When doing a literature review, it’s essential to lay a solid foundation for your exploration through a well-defined conceptual framework. This framework acts as a compass, guiding your review’s direction by establishing the key concepts, theories, and perspectives that underpin your topic. 

Definitions And Descriptions

Before diving into the depths of your literature review, it’s crucial to start with the basics. This means clearly identifying and defining the key concepts related to your topic. Think of this as setting the stage for your readers, ensuring they have a clear understanding of the fundamental terms and ideas you will be exploring.

Key Concepts Related To The Topic

Begin by listing the essential concepts central to your review. These are the building blocks of your topic, the terms that will repeatedly appear throughout your exploration. 

Detailed Definitions And Their Relevance

Once you’ve identified these concepts, provide precise and comprehensive definitions for each. Don’t hesitate to explore different dimensions or interpretations of these terms, as this can enrich your readers’ understanding. More importantly, discuss why these concepts are crucial to your review. How do they shape the scope of your exploration? How do they relate to each other and to the broader topic? This step ensures that your readers are not just familiar with the terms but also understand their significance within your review’s context.

Theoretical Perspectives

With the key concepts clearly defined, it’s time to frame your literature review within relevant theoretical perspectives. This is where you align your exploration with existing theories, models, or frameworks that provide insights into your topic.

Important Theories Related To The Topic

Identify the theories that are foundational to your topic. These could range from well-established theories that have long guided research in your field to more contemporary models that offer new insights. For example, a review of organizational behavior might draw on theories of motivation, leadership styles, and organizational culture.

Evaluation Of These Theories And Their Influence On The Topic

After pinpointing the relevant theories, critically assess their contributions to the topic. Consider questions like: How have these theories shaped understanding of the topic? What insights do they offer, and where do they fall short? Are there controversies or debates surrounding these theories? This evaluation not only deepens your review’s analytical depth but also positions your work within the larger academic conversation.

Synthesis And Evaluation In Literature Reviews

The “Synthesis and Evaluation” section is where your literature review truly comes to life. Here, you’re not just summarizing what others have said; you’re weaving together diverse strands of research to present a cohesive picture of the topic at hand.

Comparison And Contrast Of Sources

Synthesizing the literature involves more than listing findings from various studies; it’s about drawing connections between them, highlighting areas of agreement and dispute, and weaving these into a narrative that adds depth and breadth to your understanding of the topic.

Comparative Analysis

Start by grouping your sources based on similarities in their findings, methodologies, or theoretical approaches. This clustering will help you identify trends and common themes across the literature. For example, if several studies have found similar outcomes under comparable conditions, these findings can be grouped to strengthen a particular argument or observation about the topic.

Contrasts Or Conflicts Among Sources

Equally important is the identification of discrepancies in the literature. Do some studies present findings that directly contradict others? Are there differences in how researchers have interpreted similar data? Highlighting these conflicts is crucial, as it can indicate areas where the topic is still evolving or where further research is needed. It also shows your ability to critically engage with the material, a hallmark of scholarly rigor.

Analysis Of Gaps In Literature

One of your primary tasks in the synthesis and evaluation section is to identify what’s missing in the current body of research. This requires a critical eye and a deep understanding of both your topic and the broader field in which it resides.

Identification Of Research Gaps

As you comb through the literature, ask yourself: What questions remain unanswered? Are there underexplored areas or populations? Perhaps certain methodologies have been overlooked, or theoretical perspectives have not been considered. Pinpointing these gaps is not a mere exercise in academic critique; it’s a vital step in advancing knowledge within the field.

Implications Of These Gaps For Future Research

Highlighting gaps in the literature sets the stage for future studies. It’s where you, as the reviewer, can suggest new research directions that could fill these voids or further explore the topic. Discussing the implications of these gaps not only enriches your review but also contributes to the ongoing scholarly conversation. 

Conclusion For Your Literature Review

The conclusion of your literature review is where you bring together all the strands of your argument, synthesizing the insights gained and highlighting the significance of your findings. It’s not just a summary of what has been discussed; it’s an opportunity to underscore the relevance of the review, reflect on the broader implications of your synthesis and evaluation, and suggest directions for future research. 

Summary Of Key Points

Start your conclusion by succinctly summarizing the main points and findings of your review. This isn’t about rehashing every detail but rather about distilling the essence of your exploration. Highlight the critical trends, themes, and conflicts you’ve uncovered, and remind your readers of the significance of these discoveries.

Relevance And Implications Of The Literature For The Topic

Next, focus on the relevance and implications of your findings. This involves stepping back to consider the bigger picture—how does your literature review contribute to the understanding of your topic? Discuss the impact of the trends and gaps you’ve identified on the field, and elaborate on how your synthesis of the literature advances or enriches existing knowledge.

Reflection On The Research Process

Reflecting on the research process itself can provide valuable insights. Consider discussing the challenges you encountered in navigating the literature, such as dealing with conflicting findings or the scarcity of research on certain aspects of your topic. 

Directions For Future Research

One of the most critical aspects of your conclusion is to suggest directions for future research. Be as precise as possible, whether suggesting new methodologies, theoretical frameworks, or specific topics that warrant deeper investigation.

Final Thoughts

End your conclusion with a strong closing statement that reiterates the value of your literature review. Emphasize the importance of continued research on your topic and the potential it holds for advanced understanding within your field. A compelling conclusion reaffirms the significance of your work, leaving your readers with a clear sense of its contribution and the urgent need for further exploration.

Reference List In Your Literature Review

The Reference List is the backbone of your literature review, providing a comprehensive compilation of all the sources you’ve cited throughout your exploration. It’s not merely a formality but a crucial component that lends credibility and rigor to your work.

Importance Of Accuracy And Consistency

The cornerstone of a reliable Reference List is accuracy and consistency in citation style. Whether you’re adhering to APA , MLA , Chicago , or another academic citation format, it’s vital to apply the rules with precision. This includes correctly formatting author names, publication dates, titles, and publication details. 

Organizing Your References

While different citation styles have their own rules for listing references, organizing them in a way that enhances readability and accessibility is universally beneficial. Alphabetical order by the author’s last name is the most common method, as it allows readers to easily locate sources.

Comprehensive Coverage

Your Reference List should be exhaustive, including every work you’ve cited in your review. This extends beyond journal articles and books to encompass reports, conference papers, online resources, and any other materials that have informed your analysis.

The Value Of Annotations

While not always required, providing brief annotations for key sources can add tremendous value to your Reference List. An annotated bibliography offers a succinct summary of each source’s main arguments, methodologies, and findings, as well as its relevance to your literature review.

Digital Accessibility

In today’s digital age, considering the accessibility of your referenced works can greatly enhance the utility of your Reference List. Whenever possible, include Digital Object Identifiers (DOIs) or stable URLs for online sources, ensuring readers can directly access the materials. 

Also read: What Is A DOI? Exploring The Purpose And Importance

Reflecting On Ethical Scholarship

Finally, your Reference List is a reflection of ethical scholarship. By accurately citing all the sources that have informed your work, you’re honoring the intellectual property of other researchers and upholding the academic community’s standards of integrity and respect. 

Crafting a meticulous Reference List is an essential aspect of your literature review that underscores the credibility, depth, and ethical foundation of your research. By adhering to the principles of accuracy, comprehensiveness, and accessibility, you not only facilitate further inquiry but also pay homage to the collective endeavor of knowledge advancement in your field.

Related Article: Navigating the AMA Citation Format: Best Tips for Referencing

In conclusion, writing a literature review involves meticulous structuring, beginning with an engaging introduction that sets the stage, followed by a detailed exploration of the topic’s background, including its historical context and current state. 

A robust conceptual framework lays the groundwork for analysis, leading to a critical synthesis and evaluation of relevant literature. 

The conclusion ties together the review’s key findings and implications, while the reference list meticulously catalogs all cited works. Mastering each section ensures a comprehensive and insightful review, essential for advancing academic understanding and contributing to scholarly discussions.

Related Article: Preliminary Literature Review: A Guide for Effective Research

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About Sowjanya Pedada

Sowjanya is a passionate writer and an avid reader. She holds MBA in Agribusiness Management and now is working as a content writer. She loves to play with words and hopes to make a difference in the world through her writings. Apart from writing, she is interested in reading fiction novels and doing craftwork. She also loves to travel and explore different cuisines and spend time with her family and friends.

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Synthesising the literature as part of a literature review

Affiliation.

• 1 University of Manchester, England.
• PMID: 25783281
• DOI: 10.7748/ns.29.29.44.e8957

This article examines how to synthesise and critique research literature. To place the process of synthesising the research literature into context, the article explores the critiquing process by breaking it down into seven sequential steps. The article explains how and why these steps need to be kept in mind if a robust comprehensive literature search and analysis are to be achieved. The article outlines how to engage in the critiquing process and explains how the literature review needs to be assembled to generate a logical and reasoned debate to examine a topic of interest or research in more detail.

Keywords: Critical analysis; critique; evaluation; integrative review; literature review; literature search; research; research question; search strategy; synthesis.

• Research / standards*
• Research Design*
• Review Literature as Topic*

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• Volume 29, Issue 3
• Rapid reviews methods series: guidance on rapid qualitative evidence synthesis
• Article Text
• Article info
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• Rapid Responses
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• http://orcid.org/0000-0003-4808-3880 Andrew Booth 1 , 2 ,
• Isolde Sommer 3 , 4 ,
• http://orcid.org/0000-0003-4238-5984 Jane Noyes 2 , 5 ,
• Catherine Houghton 2 , 6 ,
• Fiona Campbell 1 , 7
• The Cochrane Rapid Reviews Methods Group and Cochrane Qualitative and Implementation Methods Group (CQIMG)
• 1 EnSyGN Sheffield Evidence Synthesis Group , University of Sheffield , Sheffield , UK
• 2 Cochrane Qualitative and Implementation Methods Group (CQIMG) , London , UK
• 3 Department for Evidence-based Medicine and Evaluation , University for Continuing Education Krems , Krems , Austria
• 4 Cochrane Rapid Reviews Group & Cochrane Austria , Krems , Austria
• 5 Bangor University , Bangor , UK
• 6 University of Galway , Galway , Ireland
• 7 University of Newcastle upon Tyne , Newcastle upon Tyne , UK
• Correspondence to Professor Andrew Booth, Univ Sheffield, Sheffield, UK; a.booth{at}sheffield.ac.uk

This paper forms part of a series of methodological guidance from the Cochrane Rapid Reviews Methods Group and addresses rapid qualitative evidence syntheses (QESs), which use modified systematic, transparent and reproducible methodsu to accelerate the synthesis of qualitative evidence when faced with resource constraints. This guidance covers the review process as it relates to synthesis of qualitative research. ‘Rapid’ or ‘resource-constrained’ QES require use of templates and targeted knowledge user involvement. Clear definition of perspectives and decisions on indirect evidence, sampling and use of existing QES help in targeting eligibility criteria. Involvement of an information specialist, especially in prioritising databases, targeting grey literature and planning supplemental searches, can prove invaluable. Use of templates and frameworks in study selection and data extraction can be accompanied by quality assurance procedures targeting areas of likely weakness. Current Cochrane guidance informs selection of tools for quality assessment and of synthesis method. Thematic and framework synthesis facilitate efficient synthesis of large numbers of studies or plentiful data. Finally, judicious use of Grading of Recommendations Assessment, Development and Evaluation approach for assessing the Confidence of Evidence from Reviews of Qualitative research assessments and of software as appropriate help to achieve a timely and useful review product.

• Systematic Reviews as Topic
• Patient Care

Data availability statement

No data are available. Not applicable. All data is from published articles.

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See:  http://creativecommons.org/licenses/by-nc/4.0/ .

https://doi.org/10.1136/bmjebm-2023-112620

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WHAT IS ALREADY KNOWN ON THIS TOPIC

Rapid Qualitative Evidence Synthesis (QES) is a relatively recent innovation in evidence synthesis and few published examples currently exists.

Guidance for authoring a rapid QES is scattered and requires compilation and summary.

WHAT THIS STUDY ADDS

This paper represents the first attempt to compile current guidance, illustrated by the experience of several international review teams.

We identify features of rapid QES methods that could be accelerated or abbreviated and where methods resemble those for conventional QESs.

HOW THIS STUDY MIGHT AFFECT RESEARCH, PRACTICE OR POLICY

This paper offers guidance for researchers when conducting a rapid QES and informs commissioners of research and policy-makers what to expect when commissioning such a review.

Introduction

This paper forms part of a series from the Cochrane Rapid Reviews Methods Group providing methodological guidance for rapid reviews. While other papers in the series 1–4 focus on generic considerations, we aim to provide in-depth recommendations specific to a resource-constrained (or rapid) qualitative evidence synthesis (rQES). 5 This paper is accompanied by recommended resources ( online supplemental appendix A ) and an elaboration with practical considerations ( online supplemental appendix B ).

Supplemental material

The role of qualitative evidence in decision-making is increasingly recognised. 6 This, in turn, has led to appreciation of the value of qualitative evidence syntheses (QESs) that summarise findings across multiple contexts. 7 Recognition of the need for such syntheses to be available at the time most useful to decision-making has, in turn, driven demand for rapid qualitative evidence syntheses. 8 The breadth of potential rQES mirrors the versatility of QES in general (from focused questions to broad overviews) and outputs range from descriptive thematic maps through to theory-informed syntheses (see table 1 ).

• View inline

Glossary of important terms (alphabetically)

As with other resource-constrained reviews, no one size fits all. A team should start by specifying the phenomenon of interest, the review question, 9 the perspectives to be included 9 and the sample to be determined and selected. 10 Subsequently, the team must finalise the appropriate choice of synthesis. 11 Above all, the review team should consider the intended knowledge users, 3 including requirements of the funder.

An rQES team, in particular, cannot afford any extra time or resource requirements that might arise from either a misunderstanding of the review question, an unclear picture of user requirements or an inappropriate choice of methods. The team seeks to align the review question and the requirements of the knowledge user with available time and resources. They also need to ensure that the choice of data and choice of synthesis are appropriate to the intended ‘knowledge claims’ (epistemology) made by the rQES. 11 This involves the team asking ‘what types of data are meaningful for this review question?’, ‘what types of data are trustworthy?’ and ‘is the favoured synthesis method appropriate for this type of data?’. 12 This paper aims to help rQES teams to choose methods that best fit their project while understanding the limitations of those choices. Our recommendations derive from current QES guidance, 5 evidence on modified QES methods, 8 13 and practical experience. 14 15

This paper presents an overview of considerations and recommendations as described in table 2 . Supplemental materials including additional resources details of our recommendations and practical examples are provided in online supplemental appendices A and B .

Recommendations for resource-constrained qualitative evidence synthesis (rQES)

Setting the review question and topic refinement

Rapid reviews summarise information from multiple research studies to produce evidence for ‘the public, researchers, policymakers and funders in a systematic, resource-efficient manner’. 16 Involvement of knowledge users is critical. 3 Given time constraints, individual knowledge users could be asked only to feedback on very specific decisions and tasks or on selective sections of the protocol. Specifically, whenever a QES is abbreviated or accelerated, a team should ensure that the review question is agreed by a minimum number of knowledge users with expertise or experience that reflects all the important review perspectives and with authority to approve the final version 2 5 11 ( table 2 , item R1).

Involvement of topic experts can ensure that the rQES is responsive to need. 14 17 One Cochrane rQES saved considerable time by agreeing the review topic within a single meeting and one-phase iteration. 9 Decisions on topics to be omitted are also informed by a knowledge of existing QESs. 17

An information specialist can help to manage the quantity and quality of available evidence by setting conceptual boundaries and logistic limits. A structured question format, such as Setting-Perspective-Interest, phenomenon of-Comparison-Evaluation or Population-Interest, phenomenon of-Context helps in communicating the scope and, subsequently, in operationalising study selection. 9 18

Scoping (of review parameters) and mapping (of key types of evidence and likely richness of data) helps when planning the review. 5 19 The option to choose purposive sampling over comprehensive sampling approaches, as offered by standard QES, may be particularly helpful in the context of a rapid QES. 8 Once a team knows the approximate number and distribution of studies, perhaps mapping them against country, age, ethnicity, etc), they can decide whether or not to use purposive sampling. 12 An rQES for the WHO combined purposive with variation sampling. Sampling in two stages started by reducing the initial number of studies to a more manageable sampling frame and then sampling approximately a third of the remaining studies from within the sampling frame. 20

Sampling may target richer studies and/or privilege diversity. 8 21 A rich qualitative study typically illustrates findings with verbatim extracts from transcripts from interviews or textual responses from questionnaires. Rich studies are often found in specialist qualitative research or social science journals. In contrast, less rich studies may itemise themes with an occasional indicative text extract and tend to summarise findings. In clinical or biomedical journals less rich findings may be placed within a single table or box.

No rule exists on an optimal number of studies; too many studies makes it challenging to ‘maintain insight’, 22 too few does not sustain rigorous analysis. 23 Guidance on sampling is available from the forthcoming Cochrane-Campbell QES Handbook.

A review team can use templates to fast-track writing of a protocol. The protocol should always be publicly available ( table 2 , item R2). 24 25 Formal registration may require that the team has not commenced data extraction but should be considered if it does not compromise the rQES timeframe. Time pressures may require that methods are left suitably flexible to allow well-justified changes to be made as a detailed picture of the studies and data emerge. 26 The first Cochrane rQES drew heavily on text from a joint protocol/review template previously produced within Cochrane. 24

Setting eligibility criteria

An rQES team may need to limit the number of perspectives, focusing on those most important for decision-making 5 9 27 ( table 2 , item R3). Beyond the patients/clients each additional perspective (eg, family members, health professionals, other professionals, etc) multiplies the additional effort involved.

A rapid QES may require strict date and setting restrictions 17 and language restrictions that accommodate the specific requirements of the review. Specifically, the team should consider whether changes in context over time or substantive differences between geographical regions could be used to justify a narrower date range or a limited coverage of countries and/or languages. The team should also decide if ‘indirect evidence’ is to substitute for the absence of direct evidence. An rQES typically focuses on direct evidence, except when only indirect evidence is available 28 ( table 2 , item R4). Decisions on relevance are challenging—precautions for swine influenza may inform precautions for bird influenza. 28 A smoking ban may operate similarly to seat belt legislation, etc. A review team should identify where such shared mechanisms might operate. 28 An rQES team must also decide whether to use frameworks or models to focus the review. Theories may be unearthed within the topic search or be already known to team members, fro example, Theory of Planned Behaviour. 29

Options for managing the quantity and quality of studies and data emerge during the scoping (see above). In summary, the review team should consider privileging rich qualitative studies 2 ; consider a stepwise approach to inclusion of qualitative data and explore the possibility of sampling ( table 2 , item R5). For example, where data is plentiful an rQES may be limited to qualitative research and/or to mixed methods studies. Where data is less plentiful then surveys or other qualitative data sources may need to be included. Where plentiful reviews already exist, a team may decide to conduct a review of reviews 5 by including multiple QES within a mega-synthesis 28 29 ( table 2 , item R6).

Searching for QES merits its own guidance, 21–23 30 this section reinforces important considerations from guidance specific to qualitative research. Generic guidance for rapid reviews in this series broadly applies to rapid QESs. 1

In addition to journal articles, by far the most plentiful source, qualitative research is found in book chapters, theses and in published and unpublished reports. 21 Searches to support an rQES can (a) limit the number of databases searched, deliberately selecting databases from diverse disciplines, (b) use abbreviated study filters to retrieve qualitative designs and (c) employ high yield complementary methods (eg, reference checking, citation searching and Related Articles features). An information specialist (eg, librarian) should be involved in prioritising sources and search methods ( table 2 , item R7). 11 14

According to empirical evidence optimal database combinations include Scopus plus CINAHL or Scopus plus ProQuest Dissertations and Theses Global (two-database combinations) and Scopus plus CINAHL plus ProQuest Dissertations and Theses Global (three-database combination) with both choices retrieving between 89% and 92% of relevant studies. 30

If resources allow, searches should include one or two specialised databases ( table 2 , item R8) from different disciplines or contexts 21 (eg, social science databases, specialist discipline databases or regional or institutional repositories). Even when resources are limited, the information specialist should factor in time for peer review of at least one search strategy ( table 2 , item R9). 31 Searches for ‘grey literature’ should selectively target appropriate types of grey literature (such as theses or process evaluations) and supplemental searches, including citation chaining or Related Articles features ( table 2 , item R10). 32 The first Cochrane rQES reported that searching reference lists of key papers yielded an extra 30 candidate papers for review. However, the team documented exclusion of grey literature as a limitation of their review. 15

Study selection

Consistency in study selection is achieved by using templates, by gaining a shared team understanding of the audience and purpose, and by ongoing communication within, and beyond, the team. 2 33 Individuals may work in parallel on the same task, as in the first Cochrane rQES, or follow a ‘segmented’ approach where each reviewer is allocated a different task. 14 The use of machine learning in the specific context of rQES remains experimental. However, the possibility of developing qualitative study classifiers comparable to those for randomised controlled trials offers an achievable aspiration. 34

Title and abstract screening

The entire screening team should use pre-prepared, pretested title and abstract templates to limit the scale of piloting, calibration and testing ( table 2 , item R11). 1 14 The first Cochrane rQES team double-screened titles and abstracts within Covidence review software. 14 Disagreements were resolved with reference to a third reviewer achieving a shared understanding of the eligibility criteria and enhancing familiarity with target studies and insight from data. 14 The team should target and prioritise identified risks of either over-zealous inclusion or over-exclusion specific to each rQES ( table 2 , item R12). 14 The team should maximise opportunities to capture divergent views and perspectives within study findings. 35

Full-text screening

Full-text screening similarly benefits from using a pre-prepared pretested standardised template where possible 1 14 ( table 2 , item R11). If a single reviewer undertakes full-text screening, 8 the team should identify likely risks to trustworthiness of findings and focus quality control procedures (eg, use of additional reviewers and percentages for double screening) on specific threats 14 ( table 2 , item R13). The Cochrane rQES team opted for double screening to assist their immersion within the topic. 14

Data extraction

Data extraction of descriptive/contextual data may be facilitated by review management software (eg, EPPI-Reviewer) or home-made approaches using Google Forms, or other survey software. 36 Where extraction of qualitative findings requires line-by-line coding with multiple iterations of the data then a qualitative data management analysis package, such as QSR NVivo, reaps dividends. 36 The team must decide if, collectively, they favour extracting data to a template or coding direct within an electronic version of an article.

Quality control must be fit for purpose but not excessive. Published examples typically use a single reviewer for data extraction 8 with use of two independent reviewers being the exception. The team could limit data extraction to minimal essential items. They may also consider re-using descriptive details and findings previously extracted within previous well-conducted QES ( table 2 , item R14). A pre-existing framework, where readily identified, may help to structure the data extraction template. 15 37 The same framework may be used to present the findings. Some organisations may specify a preferred framework, such as an evidence-to-decision-making framework. 38

Assessment of methodological limitations

The QES community assess ‘methodological limitations’ rather than use ‘risk of bias’ terminology. An rQES team should pick an approach appropriate to their specific review. For example, a thematic map may not require assessment of individual studies—a brief statement of the generic limitations of the set of studies may be sufficient. However, for any synthesis that underpins practice recommendations 39 assessment of included studies is integral to the credibility of findings. In any decision-making context that involves recommendations or guidelines, an assessment of methodological limitations is mandatory. 40 41

Each review team should work with knowledge users to determine a review-specific approach to quality assessment. 27 While ‘traffic lights’, similar to the outputs from the Cochrane Risk of Bias tool, may facilitate rapid interpretation, accompanying textual notes are invaluable in highlighting specific areas for concern. In particular, the rQES team should demonstrate that they are aware (a) that research designs for qualitative research seek to elicit divergent views, rather than control for variation; (b) that, for qualitative research, the selection of the sample is far more informative than the size of the sample; and (c) that researchers from primary research, and equally reviewers for the qualitative synthesis, need to be thoughtful and reflexive about their possible influences on interpretation of either the primary data or the synthesised findings.

Selection of checklist

Numerous scales and checklists exist for assessing the quality of qualitative studies. In the absence of validated risk of bias tools for qualitative studies, the team should choose a tool according to Cochrane Qualitative and Implementation Methods Group (CQIMG) guidance together with expediency (according to ease of use, prior familiarity, etc) ( table 2 , item R15). 41 In comparison to the Critical Appraisal Skills Programme checklist which was never designed for use in synthesis, 42 the Cochrane qualitative tool is similarly easy to use and was designed for QES use. Work is underway to identify an assessment process that is compatible with QESs that support decision-making. 41 For now the choice of a checklist remains determined by interim Cochrane guidance and, beyond this, by personal preference and experience. For an rQES a team could use a single reviewer to assess methodological limitations, with verification of judgements (and support statements) by a second reviewer ( table 2 , item R16).

The CQIMG endorses three types of synthesis; thematic synthesis, framework synthesis and meta-ethnography ( box 1 ). 43 44 Rapid QES favour descriptive thematic synthesis 45 or framework synthesis, 46 47 except when theory generation (meta-ethnography 48 49 or analytical thematic synthesis) is a priority ( table 2 , item R17).

Choosing a method for rapid qualitative synthesis

Thematic synthesis: first choice method for rQES. 45 For example, in their rapid QES Crooks and colleagues 44 used a thematic synthesis to understand the experiences of both academic and lived experience coresearchers within palliative and end of life research. 45

Framework synthesis: alternative where a suitable framework can be speedily identified. 46 For example, Bright and colleagues 46 considered ‘best-fit framework synthesis’ as appropriate for mapping study findings to an ‘a priori framework of dimensions measured by prenatal maternal anxiety tools’ within their ‘streamlined and time-limited evidence review’. 47

Less commonly, an adapted meta-ethnographical approach was used for an implementation model of social distancing where supportive data (29 studies) was plentiful. 48 However, this QES demonstrates several features that subsequently challenge its original identification as ‘rapid’. 49

Abbrevations: QES, qualitative evidence synthesis; rQES, resource-constrained qualitative evidence synthesis.

The team should consider whether a conceptual model, theory or framework offers a rapid way for organising, coding, interpreting and presenting findings ( table 2 , item R18). If the extracted data appears rich enough to sustain further interpretation, data from a thematic or framework synthesis can subsequently be explored within a subsequent meta-ethnography. 43 However, this requires a team with substantial interpretative expertise. 11

Assessments of confidence in the evidence 4 are central to any rQES that seeks to support decision-making and the QES-specific Grading of Recommendations Assessment, Development and Evaluation approach for assessing the Confidence of Evidence from Reviews of Qualitative research (GRADE-CERQual) approach is designed to assess confidence in qualitative evidence. 50 This can be performed by a single reviewer, confirmed by a second reviewer. 26 Additional reviewers could verify all, or a sample of, assessments. For a rapid assessment a team must prioritise findings, using objective criteria; a WHO rQES focused only on the three ‘highly synthesised findings’. 20 The team could consider reusing GRADE-CERQual assessments from published QESs if findings are relevant and of demonstrable high quality ( table 2 , item R19). 50 No rapid approach to full application of GRADE-CERQual currently exists.

Reporting and record management

Little is written on optimal use of technology. 8 A rapid review is not a good time to learn review management software or qualitative analysis management software. Using such software for all general QES processes ( table 2 , item R20), and then harnessing these skills and tools when specifically under resource pressures, is a sounder strategy. Good file labelling and folder management and a ‘develop once, re-use multi-times’ approach facilitates resource savings.

Reporting requirements include the meta-ethnography reporting guidance (eMERGe) 51 and the Enhancing transparency in reporting the synthesis of qualitative research (ENTREQ) statement. 52 An rQES should describe limitations and their implications for confidence in the evidence even more thoroughly than a regular QES; detailing the consequences of fast-tracking, streamlining or of omitting processes all together. 8 Time spent documenting reflexivity is similarly important. 27 If QES methodology is to remain credible rapid approaches must be applied with insight and documented with circumspection. 53 54 (56)

Ethics statements

Patient consent for publication.

Not applicable.

Ethics approval

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Supplementary materials

Supplementary data.

This web only file has been produced by the BMJ Publishing Group from an electronic file supplied by the author(s) and has not been edited for content.

• Data supplement 1

Correction notice Since this paper first published, updates have been made to the left hand column of table 2.

Contributors All authors (AB, IS, JN, CH, FC) have made substantial contributions to the conception and design of the guidance document. AB led on drafting the work and revising it critically for important intellectual content. All other authors (IS, JN, CH, FC) contributed to revisions of the document. All authors (AB, IS, JN, CH, FC) have given final approval of the version to be published. As members of the Cochrane Qualitative and Implementation Methods Group and/or the Cochrane Rapid Reviews Methods Group all authors (AB, IS, JN, CH, FC) agree to be accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

Competing interests AB is co-convenor of the Cochrane Qualitative and Implementation Methods Group. In the last 36 months, he received royalties from Systematic Approaches To a Successful Literature Review (Sage 3rd edition), honoraria from the Agency for Healthcare Research and Quality, and travel support from the WHO. JN is lead convenor of the Cochrane Qualitative and Implementation Methods Group. In the last 36 months, she has received honoraria from the Agency for Healthcare Research and Quality and travel support from the WHO. CH is co-convenor of the Cochrane Qualitative and Implementation Methods Group.

Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

Provenance and peer review Not commissioned; internally peer reviewed.

Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.

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Rapid literature review: definition and methodology

Beata smela.

a Assignity, Cracow, Poland

Mondher Toumi

b Public Health Department, Aix-Marseille University, Marseille, France

Karolina Świerk

Clement francois, małgorzata biernikiewicz.

c Studio Slowa, Wroclaw, Poland

Emilie Clay

d Clever-Access, Paris, France

Laurent Boyer

Introduction: A rapid literature review (RLR) is an alternative to systematic literature review (SLR) that can speed up the analysis of newly published data. The objective was to identify and summarize available information regarding different approaches to defining RLR and the methodology applied to the conduct of such reviews.

Methods: The Medline and EMBASE databases, as well as the grey literature, were searched using the set of keywords and their combination related to the targeted and rapid review, as well as design, approach, and methodology. Of the 3,898 records retrieved, 12 articles were included.

Results: Specific definition of RLRs has only been developed in 2021. In terms of methodology, the RLR should be completed within shorter timeframes using simplified procedures in comparison to SLRs, while maintaining a similar level of transparency and minimizing bias. Inherent components of the RLR process should be a clear research question, search protocol, simplified process of study selection, data extraction, and quality assurance.

Conclusions: There is a lack of consensus on the formal definition of the RLR and the best approaches to perform it. The evidence-based supporting methods are evolving, and more work is needed to define the most robust approaches.

Introduction

A systematic literature review (SLR) summarizes the results of all available studies on a specific topic and provides a high level of evidence. Authors of the SLR have to follow an advanced plan that covers defining a priori information regarding the research question, sources they are going to search, inclusion criteria applied to choose studies answering the research question, and information regarding how they are going to summarize findings [ 1 ].

The rigor and transparency of SLRs make them the most reliable form of literature review [ 2 ], providing a comprehensive, objective summary of the evidence for a given topic [ 3 , 4 ]. On the other hand, the SLR process is usually very time-consuming and requires a lot of human resources. Taking into account a high increase of newly published data and a growing need to analyze information in the fastest possible way, rapid literature reviews (RLRs) often replace standard SLRs.

There are several guidelines on the methodology of RLRs [ 5–11 ]; however, only recently, one publication from 2021 attempted to construct a unified definition [ 11 ]. Generally, by RLRs, researchers understand evidence synthesis during which some of the components of the systematic approach are being used to facilitate answering a focused research question; however, scope restrictions and a narrower search strategy help to make the project manageable in a shorter time and to get the key conclusions faster [ 4 ].

The objective of this research was to collect and summarize available information on different approaches to the definition and methodology of RLRs. An RLR has been run to capture publications providing data that fit the project objective.

To find publications reporting information on the methodology of RLRs, searches were run in the Medline and EMBASE databases in November 2022. The following keywords were searched for in titles and abstracts: ‘targeted adj2 review’ OR ‘focused adj2 review’ OR ‘rapid adj2 review’, and ‘methodology’ OR ‘design’ OR ‘scheme’ OR ‘approach’. The grey literature was identified using Google Scholar with keywords including ‘targeted review methodology’ OR ‘focused review methodology’ OR ‘rapid review methodology’. Only publications in English were included, and the date of publication was restricted to year 2016 onward in order to identify the most up-to-date literature. The reference lists of each included article were searched manually to obtain the potentially eligible articles. Titles and abstracts of the retrieved records were first screened to exclude articles that were evidently irrelevant. The full texts of potentially relevant papers were further reviewed to examine their eligibility.

A pre-defined Excel grid was developed to extract the following information related to the methodology of RLR from guidelines:

• Definition,
• Research question and searches,
• Studies selection,
• Data extraction and quality assessment,
• Additional information.

There was no restriction on the study types to be analyzed; any study reporting on the methodology of RLRs could be included: reviews, practice guidelines, commentaries, and expert opinions on RLR relevant to healthcare policymakers or practitioners. The data extraction and evidence summary were conducted by one analyst and further examined by a senior analyst to ensure that relevant information was not omitted. Disagreements were resolved by discussion and consensus.

Studies selection

A total of 3,898 records (3,864 articles from a database search and 34 grey literature from Google Scholar) were retrieved. After removing duplicates, titles and abstracts of 3,813 articles were uploaded and screened. The full texts of 43 articles were analyzed resulting in 12 articles selected for this review, including 7 guidelines [ 5–11 ] on the methodology of RLRs, together with 2 papers summarizing the results of the Delphi consensus on the topic [ 12 , 13 ], and 3 publications analyzing and assessing different approaches to RLRs [ 4 , 14 , 15 ].

Overall, seven guidelines were identified: from the World Health Organization (WHO) [ 5 ], National Collaborating Centre for Methods and Tools (NCCMT) [ 7 ], the UK government [ 8 ], the Oxford Centre for Evidence Based Medicine [ 9 ], the Cochrane group [ 6 , 11 ], and one multi-national review [ 10 ]. Among the papers that did not describe the guidelines, Gordon et al. [ 4 ] proposed 12 tips for conducting a rapid review in the right settings and discussed why these reviews may be more beneficial in some circumstances. The objective of work conducted by Tricco et al. [ 13 ] and Pandor et al. [ 12 ] was to collect and compare perceptions of rapid reviews from stakeholders, including researchers, policymakers, industry, journal editors, and healthcare providers, and to reach a consensus outlining the domains to consider when deciding on approaches for RLRs. Haby et al. [ 14 ] run a rapid review of systematic reviews and primary studies to find out the best way to conduct an RLR in health policy and practice. In Tricco et al. (2022) [ 15 ], JBI position statement for RLRs is presented.

From all the seven identified guidelines information regarding definitions the authors used for RLRs, approach to the PICOS criteria and search strategy development, studies selection, data extractions, quality assessment, and reporting were extracted.

Cochrane Rapid Reviews Methods Group developed methods guidance based on scoping review of the underlying evidence, primary methods studies conducted, as well as surveys sent to Cochrane representative and discussion among those with expertise [ 11 ]. They analyzed over 300 RLRs or RLR method papers and based on the methodology of those studies, constructed a broad definition RLR, one that meets a minimum set of requirements identified in the thematic analysis: ‘ A rapid review is a form of knowledge synthesis that accelerates the process of conducting a traditional systematic review through streamlining or omitting a variety of methods to produce evidence in a resource-efficient manner .’ This interpretation aligns with more than 50% of RLRs identified in this study. The authors additionally provided several other definitions, depending on specific situations or requirements (e.g., when RLR is produced on stakeholder’s request). It was additionally underlined that RLRs should be driven by the need of timely evidence for decision-making purposes [ 11 ].

Rapid reviews vary in their objective, format, and methods used for evidence synthesis. This is a quite new area, and still no agreement on optimal methods can be found [ 5 ]. All of the definitions are highlighting that RLRs are completed within shorter timeframes than SLRs, and also lack of time is one of the main reasons they are conducted. It has been suggested that most rapid reviews are conducted within 12 weeks; however, some of the resources suggest time between a few weeks to no more than 6 months [ 5 , 6 ]. Some of the definitions are highlighting that RLRs follow the SLR process, but certain phases of the process are simplified or omitted to retrieve information in a time-saving way [ 6 , 7 ]. Different mechanisms are used to enhance the timeliness of reviews. They can be used independently or concurrently: increasing the intensity of work by intensifying the efforts of multiple analysts by parallelization of tasks, using review shortcuts whereby one or more systematic review steps may be reduced, automatizing review steps by using new technologies [ 5 ]. The UK government report [ 8 ] referred to two different RLRs: in the form of quick scoping reviews (QSR) or rapid evidence assessments (REA). While being less resource and time-consuming compared to standard SLRs, QSRs and REAs are designed to be similarly transparent and to minimize bias. QSRs can be applied to rather open-ended questions, e.g., ‘what do we know about something’ but both, QSRs and REAs, provide an understanding of the volume and characteristics of evidence on a specific topic, allowing answering questions by maximizing the use of existing data, and providing a clear picture of the adequacy of existing evidence [ 8 ].

Research questions and searches

The guidelines suggest creating a clear research question and search protocol at the beginning of the project. Additionally, to not duplicate RLRs, the Cochrane Rapid Reviews Methods Group encourages all people working on RLRs to consider registering their search protocol with PROSPERO, the international prospective register of reviews; however, so far they are not formally registered in most cases [ 5 , 6 ]. They also recommend involving key stakeholders (review users) to set and refine the review question, criteria, and outcomes, as well as consulting them through the entire process [ 11 ].

Regarding research questions, it is better to structure them in a neutral way rather than focus on a specific direction for the outcome. By doing so, the researcher is in a better position to identify all the relevant evidence [ 7 ]. Authors can add a second, supportive research question when needed [ 8 ]. It is encouraged to limit the number of interventions, comparators and outcomes, to focus on the ones that are most important for decision-making [ 11 ]. Useful could be also reviewing additional materials, e.g., SLRs on the topic, as well as conducting a quick literature search to better understand the topic before starting with RLRs [ 7 ]. In SLRs researchers usually do not need to care a lot about time spent on creating PICOS, they need to make sure that the scope is broad enough, and they cannot use many restrictions. When working on RLRs, a reviewer may spend more or less time defining each of the components of the study question, and the main step is making sure that PICOS addresses the needs of those who requested the rapid review, and at the same time, it is feasible within the required time frame [ 7 ]. Search protocol should contain an outline of how the following review steps are to be carried out, including selected search keywords and a full strategy, a list of data sources, precise inclusion and exclusion criteria, a strategy for data extraction and critical appraisal, and a plan of how the information will be synthesized [ 8 ].

In terms of searches running, in most cases, an exhaustive process will not be feasible. Researchers should make sure that the search is effective and efficient to produce results in a timely manner. Cochrane Rapid Reviews Methods Group recommends involving an information specialist and conducting peer review of at least one search strategy [ 11 ]. According to the rapid review guidebook by McMaster University [ 7 ], it is important that RLRs, especially those that support policy and program decisions, are being fed by the results of a body of literature, rather than single studies, when possible. It would result in more generalizable findings applied at the level of a population and serve more realistic findings for program decisions [ 7 ]. It is important to document the search strategy, together with a record of the date and any date limits of the search, so that it can easily be run again, modified, or updated. Furthermore, the information on the individual databases included in platform services should always be reported, as this depends on organizations’ subscriptions and must be included for transparency and repeatability [ 7 , 8 ]. Good solution for RLRs is narrowing the scope or searching a limited number of databases and other sources [ 7 ]. Often, the authors use the PubMed/MEDLINE, Cochrane Library, and Embase databases. In most reviews, two or more databases are searched, and common limits are language (usually restricted to English), date, study design, and geographical area. Some RLRs include searching of grey literature; however, contact with authors is rather uncommon [ 5 , 8 ]. According to the flexible framework for restricted systematic review published by the University of Oxford, the search should be run in at least one major scientific database such as PubMed, and one other source, e.g., Google Scholar [ 9 ]. Grey literature and unpublished evidence may be particularly needed and important for intervention questions. It is related to the fact that studies that do not report the effects of interventions are less likely to be published [ 8 ]. If there is any type of evidence that will not be considered by the RLRs, e.g., reviews or theoretical and conceptual studies, it should also be stated in the protocol together with justification [ 8 ]. Additionally, authors of a practical guide published by WHO suggest using a staged search to identify existing SLRs at the beginning, and then focusing on studies with other designs [ 5 ]. If a low number of citations have been retrieved, it is acceptable to expand searches, remove some of the limits, and add additional databases and sources [ 7 ].

Searching for RLRs is an iterative process, and revising the approach is usually needed [ 7 ]. Changes should be confirmed with stakeholders and should be tracked and reflected in the final report [ 5 ].

The next step in the rapid review is the selection of studies consisting of two phases: screening of titles and abstracts, and analysis of full texts. Prior to screening initiation, it is recommended to conduct a pilot exercise using the same 30–50 abstracts and 5–10 full-texts for the entire screening team in order to calibrate and test the review form [ 11 ]. In contrast to SLRs, it can be done by one reviewer with or without verification by a second one. If verification is performed, usually the second reviewer checks only a subset of records and compares them. Cochrane Group, in contrast, recommends a stricter approach: at least 20% of references should be double-screened at titles and abstracts stage, and while the rest of the references may be screened by one reviewer, the excluded items need to be re-examined by second reviewer; similar approach is used in full-text screening [ 11 ]. This helps to ensure that bias was reduced and that the PICOS criteria are applied in a relevant way [ 5 , 8 , 9 , 11 ]. During the analysis of titles and abstracts, there is no need to report reasons for exclusion; however, they should be tracked for all excluded full texts [ 7 ].

Data extraction and quality assessment

According to the WHO guide, the most common method for data extraction in RLRs is extraction done by a single reviewer with or without partial verification. The authors point out that a reasonable approach is to use a second reviewer to check a random sample of at least 10% of the extractions for accuracy. Dual performance is more necessary for the extraction of quantitative results than for descriptive study information. In contrast, Cochrane group recommends that second reviewer should check the correctness and completeness of all data [ 11 ]. When possible, extractions should be limited to key characteristics and outcomes of the study. The same approach to data extraction is also suggested for a quality assessment process within rapid reviews [ 5 , 9 , 11 ]. Authors of the guidebook from McMaster University highlight that data extraction should be done ideally by two reviewers independently and consensus on the discrepancies should always be reached [ 7 ]. The final decision on the approach to this important step of review should depend on the available time and should also reflect the complexity of the research question [ 9 ].

For screening, analysis of full texts, extractions, and quality assessments, researchers can use information technologies to support them by making these review steps more efficient [ 5 ].

Before data reporting, a reviewer should prepare a document with key message headings, executive summary, background related to the topic and status of the current knowledge, project question, synthesis of findings, conclusions, and recommendations. According to the McMaster University guidebook, a report should be structured in a 1:2:20 format, that is, one page for key messages, two pages for an executive summary, and a full report of up to 20 pages [ 7 ]. All the limitations of the RLRs should be analyzed, and conclusions should be drawn with caution [ 5 ]. The quality of the accumulated evidence and the strength of recommendations can be assessed using, e.g., the GRADE system [ 5 ]. When working on references quoting, researchers should remember to use a primary source, not secondary references [ 7 ]. It would be worth considering the support of some software tools to automate reporting steps. Additionally, any standardization of the process and the usage of templates can support report development and enhance the transparency of the review [ 5 ].

Ideally, all the review steps should be completed during RLRs; however, often some steps may need skipping or will not be completed as thoroughly as should because of time constraints. It is always crucial to decide which steps may be skipped, and which are the key ones, depending on the project [ 7 ]. Guidelines suggest that it may be helpful to invite researchers with experience in the operations of SLRs to participate in the rapid review development [ 5 , 9 ]. As some of the steps will be completed by one reviewer only, it is important to provide them with relevant training at the beginning of the process, as well as during the review, to minimize the risk of mistakes [ 5 ].

Additional information

Depending on the policy goal and available resources and deadlines, methodology of the RLRs may be modified. Wilson et al. [ 10 ] provided extensive guidelines for performing RLR within days (e.g., to inform urgent internal policy discussions and/or management decisions), weeks (e.g., to inform public debates), or months (e.g., to inform policy development cycles that have a longer timeline, but that cannot wait for a traditional full systematic review). These approaches vary in terms of data synthesis, types of considered evidence and project management considerations.

In shortest timeframes, focused questions and subquestions should be formulated, typically to conduct a policy analysis; the report should consist of tables along with a brief narrative summary. Evidence from SLRs is often considered, as well as key informant interviews may be conducted to identify additional literature and insights about the topic, while primary studies and other types of evidence are not typically feasible due to time restrictions. The review would be best conducted with 1–2 reviewers sharing the work, enabling rapid iterations of the review. As for RLRs with longer timeline (weeks), these may use a mix of policy, systems and political analysis. Structure of the review would be similar to shorter RLRs – tabular with short narrative summary, as the timeline does not allow for comprehensive synthesis of data. Besides SLRs, primary studies and other evidence may be feasible in this timeframe, if obtained using the targeted searches in the most relevant databases. The review team should be larger, and standardized procedures for reviewing of the results and data extraction should be applied. In contrast to previous timeframe, merit review process may be feasible. For both timeframes, brief consultations with small transdisciplinary team should be conducted at the beginning and in the final stage of the review to discuss important matters.

For RLRs spanning several months, more comprehensive methodology may be adapted in terms of data synthesis and types of evidence. However, authors advise that review may be best conducted with a small review team in order to allow for more in-depth interpretation and iteration.

Studies analyzing methodology

There have been two interesting publications summarizing the results of Delphi consensus on the RLR methodology identified and included in this review [ 12 , 13 ].

Tricco et al. [ 13 ] first conducted an international survey and scoping review to collect information on the possible approaches to the running of rapid reviews, based on which, they employed a modified Delphi method that included inputs from 113 stakeholders to explore the most optimized approach. Among the six most frequent rapid review approaches (not all detailed here) being evaluated, the approach that combines inclusion of published literature only, a search of more than one database and limitations by date and language, study selection by one analyst, data extraction, and quality assessment by one analyst and one verifier, was perceived as the most feasible approach (72%, 81/113 responses) with the potentially lowest risk of bias (12%, 12/103). The approach ranked as the first one when considering timelines assumes updating of the search from a previously published review, no additional limits on search, studies selection and data extraction done by one reviewer, and no quality assessment. Finally, based on the publication, the most comprehensive RLRs can be made by moving on with the following rules: searching more than one database and grey literature and using date restriction, and assigning one reviewer working on screening, data extraction, and risk of bias assessment ( Table 1 ). Pandor et al. [ 12 ] introduced a decision tool for SelecTing Approaches for Rapid Reviews (STARR) that were produced through the Delphi consensus of international experts through an iterative and rigorous process. Participants were asked to assess the importance of predefined items in four domains related to the rapid review process: interaction with commissioners, understanding the evidence base, data extraction and synthesis methods, and reporting of rapid review methods. All items assigned to four domains achieved > 70% of consensus, and in that way, the first consensus-driven tool has been created that supports authors of RLRs in planning and deciding on approaches.

Six most frequent approaches to RLRs (adapted from Tricco et al. [ 13 ]).

Haby et al. [ 14 ] run searches of 11 databases and two websites and developed a comprehensive overview of the methodology of RLRs. With five SLRs and one RCT being finally included, they identified the following approaches used in RLRs to make them faster than full SLRs: limiting the number and scope of questions, searching fewer databases, limited searching of grey literature, restrictions on language and date (e.g., English only, most recent publications), updating the existing SLRs, eliminating or limiting hand searches of reference lists, noniterative search strategies, eliminating consultation with experts, limiting dual study selection, data extraction and quality assessment, minimal data synthesis with short concise conclusions or recommendations. All the SLRs included in this review were consistent in stating that no agreed definition of rapid reviews is available, and there is still no final agreement on the best methodological rules to be followed.

Gordon et al. [ 4 ] explained the advantages of performing a focused review and provided 12 tips for its conduction. They define focused reviews as ‘a form of knowledge synthesis in which the components of the systematic process are applied to facilitate the analysis of a focused research question’. The first tip presented by the authors is related to deciding if a focused review is a right solution for the considered project. RLRs will suit emerging topics, approaches, or assessments where early synthesis can support doctors, policymakers, etc., but also can direct future research. The second, third, and fourth tips highlight the importance of running preliminary searches and considering narrowing the results by using reasonable constraints taking into account the local context, problems, efficiency perspectives, and available time. Further tips include creating a team of experienced reviewers working on the RLRs, thinking about the target journal from the beginning of work on the rapid review, registering the search protocol on the PROSPERO registry, and the need for contacting authors of papers when data available in publications are missing or incongruent. The last three tips are related to the choice of evidence synthesis method, using the visual presentation of data, and considering and describing all the limitations of the focused review.

Finally, a new publication by Tricco et al. from 2022, describing JBI position statement [ 15 ] underlined that for the time being, there is no specific tool for critical appraisal of the RLR’s methodological quality. Instead, reviewers may use available tools to assess the risk of bias or quality of SLRs, like ROBIS, the JBI critical appraisal tools, or the assessment of multiple systematic reviews (AMSTAR).

Inconsistency in the definitions and methodologies of RLR

Although RLR was broadly perceived as an approach to quicken the conduct of conventional SLR, there is a lack of consensus on the formal definition of the RLR, so as to the best approaches to perform it. Only in 2021, a study proposing unified definition was published; however, it is important to note that the most accurate definition was only matching slightly over 50% of papers analysed by the authors, which underlines the lack of homogeneity in the field [ 11 ]. The evidence-based supporting methods are evolving, and more evidence is needed to define the most robust approaches [ 5 ].

Diverse terms are used to describe the RLR, including ‘rapid review’, focused systematic review’, ‘quick scoping reviews’, and ‘rapid evidence assessments’. Although the general principles of conducting RLR are to accelerate the whole process, complexity was seen in the methodologies used for RLRs, as reflected in this study. Also, inconsistencies related to the scope of the questions, search strategies, inclusion criteria, study screening, full-text review, quality assessment, and evidence presentation were implied. All these factors may hamper decision-making about optimal methodologies for conducting rapid reviews, and as a result, the efficiency of RLR might be decreased. Additionally, researchers may tend to report the methodology of their reviews without a sufficient level of detail, making it difficult to appraise the quality and robustness of their work.

Advantages and weaknesses of RLR

Although RLR used simplified approaches for evidence synthesis compared with SLR, the methodologies for RLR should be replicable, rigorous, and transparent to the greatest extent [ 16 ]. When time and resources are limited, RLR could be a practical and efficient tool to provide the summary of evidence that is critical for making rapid clinical or policy-related decisions [ 5 ]. Focusing on specific questions that are of controversy or special interest could be powerful in reaffirming whether the existing recommendation statements are still appropriate [ 17 ].

The weakness of RLR should also be borne in mind, and the trade-off of using RLR should be carefully considered regarding the thoroughness of the search, breadth of a research question, and depth of analysis [ 18 ]. If allowed, SLR is preferred over RLR considering that some relevant studies might be omitted with narrowed search strategies and simplified screening process [ 14 ]. Additionally, omitting the quality assessment of included studies could result in an increased risk of bias, making the comprehensiveness of RLR compromised [ 13 ]. Furthermore, in situations that require high accuracy, for example, where a small relative difference in an intervention has great impacts, for the purpose of drafting clinical guidelines, or making licensing decisions, a comprehensive SLR may remain the priority [ 19 ]. Therefore, clear communications with policymakers are recommended to reach an agreement on whether an RLR is justified and whether the methodologies of RLR are acceptable to address the unanswered questions [ 18 ].

Disclosure statement

No potential conflict of interest was reported by the author(s).