systematic review begins their research work by asking

Introduction to Systematic Reviews

In this guide.

• Introduction
• Lane Research Services
• Types of Reviews
• Systematic Review Process
• Protocols & Guidelines
• Data Extraction and Screening
• Resources & Tools
• Systematic Review Online Course

What is a Systematic Review?

Knowledge synthesis is a term used to describe the method of synthesizing results from individual studies and interpreting these results within the larger body of knowledge on the topic. It requires highly structured, transparent and reproducible methods using quantitative and/or qualitative evidence. Systematic reviews, meta-analyses, scoping reviews, rapid reviews, narrative syntheses, practice guidelines, among others, are all forms of knowledge syntheses. For more information on types of reviews, visit the "Types of Reviews" tab on the left.

A systematic review varies from an ordinary literature review in that it uses a comprehensive, methodical, transparent and reproducible search strategy to ensure conclusions are as unbiased and closer to the truth as possible. The Cochrane Handbook for Systematic Reviews of Interventions  defines a systematic review as:

"A systematic review attempts to identify, appraise and synthesize all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question. Researchers conducting systematic reviews use explicit methods aimed at minimizing bias, in order to produce more reliable findings that can be used to inform decision making [...] This involves: the a priori specification of a research question; clarity on the scope of the review and which studies are eligible for inclusion; making every effort to find all relevant research and to ensure that issues of bias in included studies are accounted for; and analysing the included studies in order to draw conclusions based on all the identified research in an impartial and objective way." ( Chapter 1: Starting a review )

What are systematic reviews? from Cochrane on Youtube .

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How to Write a Systematic Review: A Narrative Review

Ali hasanpour dehkordi.

Social Determinants of Health Research Center, Shahrekord University of Medical Sciences, Shahrekord, Iran

Elaheh Mazaheri

1 Health Information Technology Research Center, Student Research Committee, Department of Medical Library and Information Sciences, School of Management and Medical Information Sciences, Isfahan University of Medical Sciences, Isfahan, Iran

Hanan A. Ibrahim

2 Department of International Relations, College of Law, Bayan University, Erbil, Kurdistan, Iraq

Sahar Dalvand

3 MSc in Biostatistics, Health Promotion Research Center, Iran University of Medical Sciences, Tehran, Iran

Reza Ghanei Gheshlagh

4 Spiritual Health Research Center, Research Institute for Health Development, Kurdistan University of Medical Sciences, Sanandaj, Iran

In recent years, published systematic reviews in the world and in Iran have been increasing. These studies are an important resource to answer evidence-based clinical questions and assist health policy-makers and students who want to identify evidence gaps in published research. Systematic review studies, with or without meta-analysis, synthesize all available evidence from studies focused on the same research question. In this study, the steps for a systematic review such as research question design and identification, the search for qualified published studies, the extraction and synthesis of information that pertain to the research question, and interpretation of the results are presented in details. This will be helpful to all interested researchers.

A systematic review, as its name suggests, is a systematic way of collecting, evaluating, integrating, and presenting findings from several studies on a specific question or topic.[ 1 ] A systematic review is a research that, by identifying and combining evidence, is tailored to and answers the research question, based on an assessment of all relevant studies.[ 2 , 3 ] To identify assess and interpret available research, identify effective and ineffective health-care interventions, provide integrated documentation to help decision-making, and identify the gap between studies is one of the most important reasons for conducting systematic review studies.[ 4 ]

In the review studies, the latest scientific information about a particular topic is criticized. In these studies, the terms of review, systematic review, and meta-analysis are used instead. A systematic review is done in one of two methods, quantitative (meta-analysis) and qualitative. In a meta-analysis, the results of two or more studies for the evaluation of say health interventions are combined to measure the effect of treatment, while in the qualitative method, the findings of other studies are combined without using statistical methods.[ 5 ]

Since 1999, various guidelines, including the QUORUM, the MOOSE, the STROBE, the CONSORT, and the QUADAS, have been introduced for reporting meta-analyses. But recently the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement has gained widespread popularity.[ 6 , 7 , 8 , 9 ] The systematic review process based on the PRISMA statement includes four steps of how to formulate research questions, define the eligibility criteria, identify all relevant studies, extract and synthesize data, and deduce and present results (answers to research questions).[ 2 ]

Systematic Review Protocol

Systematic reviews start with a protocol. The protocol is a researcher road map that outlines the goals, methodology, and outcomes of the research. Many journals advise writers to use the PRISMA statement to write the protocol.[ 10 ] The PRISMA checklist includes 27 items related to the content of a systematic review and meta-analysis and includes abstracts, methods, results, discussions, and financial resources.[ 11 ] PRISMA helps writers improve their systematic review and meta-analysis report. Reviewers and editors of medical journals acknowledge that while PRISMA may not be used as a tool to assess the methodological quality, it does help them to publish a better study article [ Figure 1 ].[ 12 ]

Screening process and articles selection according to the PRISMA guidelines

The main step in designing the protocol is to define the main objectives of the study and provide some background information. Before starting a systematic review, it is important to assess that your study is not a duplicate; therefore, in search of published research, it is necessary to review PREOSPERO and the Cochrane Database of Systematic. Sometimes it is better to search, in four databases, related systematic reviews that have already been published (PubMed, Web of Sciences, Scopus, Cochrane), published systematic review protocols (PubMed, Web of Sciences, Scopus, Cochrane), systematic review protocols that have already been registered but have not been published (PROSPERO, Cochrane), and finally related published articles (PubMed, Web of Sciences, Scopus, Cochrane). The goal is to reduce duplicate research and keep up-to-date systematic reviews.[ 13 ]

Research questions

Writing a research question is the first step in systematic review that summarizes the main goal of the study.[ 14 ] The research question determines which types of studies should be included in the analysis (quantitative, qualitative, methodic mix, review overviews, or other studies). Sometimes a research question may be broken down into several more detailed questions.[ 15 ] The vague questions (such as: is walking helpful?) makes the researcher fail to be well focused on the collected studies or analyze them appropriately.[ 16 ] On the other hand, if the research question is rigid and restrictive (e.g., walking for 43 min and 3 times a week is better than walking for 38 min and 4 times a week?), there may not be enough studies in this area to answer this question and hence the generalizability of the findings to other populations will be reduced.[ 16 , 17 ] A good question in systematic review should include components that are PICOS style which include population (P), intervention (I), comparison (C), outcome (O), and setting (S).[ 18 ] Regarding the purpose of the study, control in clinical trials or pre-poststudies can replace C.[ 19 ]

Search and identify eligible texts

After clarifying the research question and before searching the databases, it is necessary to specify searching methods, articles screening, studies eligibility check, check of the references in eligible studies, data extraction, and data analysis. This helps researchers ensure that potential biases in the selection of potential studies are minimized.[ 14 , 17 ] It should also look at details such as which published and unpublished literature have been searched, how they were searched, by which mechanism they were searched, and what are the inclusion and exclusion criteria.[ 4 ] First, all studies are searched and collected according to predefined keywords; then the title, abstract, and the entire text are screened for relevance by the authors.[ 13 ] By screening articles based on their titles, researchers can quickly decide on whether to retain or remove an article. If more information is needed, the abstracts of the articles will also be reviewed. In the next step, the full text of the articles will be reviewed to identify the relevant articles, and the reason for the removal of excluded articles is reported.[ 20 ] Finally, it is recommended that the process of searching, selecting, and screening articles be reported as a flowchart.[ 21 ] By increasing research, finding up-to-date and relevant information has become more difficult.[ 22 ]

Currently, there is no specific guideline as to which databases should be searched, which database is the best, and how many should be searched; but overall, it is advisable to search broadly. Because no database covers all health topics, it is recommended to use several databases to search.[ 23 ] According to the A MeaSurement Tool to Assess Systematic Reviews scale (AMSTAR) at least two databases should be searched in systematic and meta-analysis, although more comprehensive and accurate results can be obtained by increasing the number of searched databases.[ 24 ] The type of database to be searched depends on the systematic review question. For example, in a clinical trial study, it is recommended that Cochrane, multi-regional clinical trial (mRCTs), and International Clinical Trials Registry Platform be searched.[ 25 ]

For example, MEDLINE, a product of the National Library of Medicine in the United States of America, focuses on peer-reviewed articles in biomedical and health issues, while Embase covers the broad field of pharmacology and summaries of conferences. CINAHL is a great resource for nursing and health research and PsycINFO is a great database for psychology, psychiatry, counseling, addiction, and behavioral problems. Also, national and regional databases can be used to search related articles.[ 26 , 27 ] In addition, the search for conferences and gray literature helps to resolve the file-drawn problem (negative studies that may not be published yet).[ 26 ] If a systematic review is carried out on articles in a particular country or region, the databases in that region or country should also be investigated. For example, Iranian researchers can use national databases such as Scientific Information Database and MagIran. Comprehensive search to identify the maximum number of existing studies leads to a minimization of the selection bias. In the search process, the available databases should be used as much as possible, since many databases are overlapping.[ 17 ] Searching 12 databases (PubMed, Scopus, Web of Science, EMBASE, GHL, VHL, Cochrane, Google Scholar, Clinical trials.gov, mRCTs, POPLINE, and SIGLE) covers all articles published in the field of medicine and health.[ 25 ] Some have suggested that references management software be used to search for more easy identification and removal of duplicate articles from several different databases.[ 20 ] At least one search strategy is presented in the article.[ 21 ]

Quality assessment

The methodological quality assessment of articles is a key step in systematic review that helps identify systemic errors (bias) in results and interpretations. In systematic review studies, unlike other review studies, qualitative assessment or risk of bias is required. There are currently several tools available to review the quality of the articles. The overall score of these tools may not provide sufficient information on the strengths and weaknesses of the studies.[ 28 ] At least two reviewers should independently evaluate the quality of the articles, and if there is any objection, the third author should be asked to examine the article or the two researchers agree on the discussion. Some believe that the study of the quality of studies should be done by removing the name of the journal, title, authors, and institutions in a Blinded fashion.[ 29 ]

There are several ways for quality assessment, such as Sack's quality assessment (1988),[ 30 ] overview quality assessment questionnaire (1991),[ 31 ] CASP (Critical Appraisal Skills Program),[ 32 ] and AMSTAR (2007),[ 33 ] Besides, CASP,[ 34 ] the National Institute for Health and Care Excellence,[ 35 ] and the Joanna Briggs Institute System for the Unified Management, Assessment and Review of Information checklists.[ 30 , 36 ] However, it is worth mentioning that there is no single tool for assessing the quality of all types of reviews, but each is more applicable to some types of reviews. Often, the STROBE tool is used to check the quality of articles. It reviews the title and abstract (item 1), introduction (items 2 and 3), implementation method (items 4–12), findings (items 13–17), discussion (Items 18–21), and funding (item 22). Eighteen items are used to review all articles, but four items (6, 12, 14, and 15) apply in certain situations.[ 9 ] The quality of interventional articles is often evaluated by the JADAD tool, which consists of three sections of randomization (2 scores), blinding (2 scores), and patient count (1 scores).[ 29 ]

Data extraction

At this stage, the researchers extract the necessary information in the selected articles. Elamin believes that reviewing the titles and abstracts and data extraction is a key step in the review process, which is often carried out by two of the research team independently, and ultimately, the results are compared.[ 37 ] This step aimed to prevent selection bias and it is recommended that the chance of agreement between the two researchers (Kappa coefficient) be reported at the end.[ 26 ] Although data collection forms may differ in systematic reviews, they all have information such as first author, year of publication, sample size, target community, region, and outcome. The purpose of data synthesis is to collect the findings of eligible studies, evaluate the strengths of the findings of the studies, and summarize the results. In data synthesis, we can use different analysis frameworks such as meta-ethnography, meta-analysis, or thematic synthesis.[ 38 ] Finally, after quality assessment, data analysis is conducted. The first step in this section is to provide a descriptive evaluation of each study and present the findings in a tabular form. Reviewing this table can determine how to combine and analyze various studies.[ 28 ] The data synthesis approach depends on the nature of the research question and the nature of the initial research studies.[ 39 ] After reviewing the bias and the abstract of the data, it is decided that the synthesis is carried out quantitatively or qualitatively. In case of conceptual heterogeneity (systematic differences in the study design, population, and interventions), the generalizability of the findings will be reduced and the study will not be meta-analysis. The meta-analysis study allows the estimation of the effect size, which is reported as the odds ratio, relative risk, hazard ratio, prevalence, correlation, sensitivity, specificity, and incidence with a confidence interval.[ 26 ]

Estimation of the effect size in systematic review and meta-analysis studies varies according to the type of studies entered into the analysis. Unlike the mean, prevalence, or incidence index, in odds ratio, relative risk, and hazard ratio, it is necessary to combine logarithm and logarithmic standard error of these statistics [ Table 1 ].

Effect size in systematic review and meta-analysis

OR=Odds ratio; RR=Relative risk; RCT= Randomized controlled trial; PPV: positive predictive value; NPV: negative predictive value; PLR: positive likelihood ratio; NLR: negative likelihood ratio; DOR: diagnostic odds ratio

Interpreting and presenting results (answers to research questions)

A systematic review ends with the interpretation of results. At this stage, the results of the study are summarized and the conclusions are presented to improve clinical and therapeutic decision-making. A systematic review with or without meta-analysis provides the best evidence available in the hierarchy of evidence-based practice.[ 14 ] Using meta-analysis can provide explicit conclusions. Conceptually, meta-analysis is used to combine the results of two or more studies that are similar to the specific intervention and the similar outcomes. In meta-analysis, instead of the simple average of the results of various studies, the weighted average of studies is reported, meaning studies with larger sample sizes account for more weight. To combine the results of various studies, we can use two models of fixed and random effects. In the fixed-effect model, it is assumed that the parameters studied are constant in all studies, and in the random-effect model, the measured parameter is assumed to be distributed between the studies and each study has measured some of it. This model offers a more conservative estimate.[ 40 ]

Three types of homogeneity tests can be used: (1) forest plot, (2) Cochrane's Q test (Chi-squared), and (3) Higgins I 2 statistics. In the forest plot, more overlap between confidence intervals indicates more homogeneity. In the Q statistic, when the P value is less than 0.1, it indicates heterogeneity exists and a random-effect model should be used.[ 41 ] Various tests such as the I 2 index are used to determine heterogeneity, values between 0 and 100; the values below 25%, between 25% and 50%, and above 75% indicate low, moderate, and high levels of heterogeneity, respectively.[ 26 , 42 ] The results of the meta-analyzing study are presented graphically using the forest plot, which shows the statistical weight of each study with a 95% confidence interval and a standard error of the mean.[ 40 ]

The importance of meta-analyses and systematic reviews in providing evidence useful in making clinical and policy decisions is ever-increasing. Nevertheless, they are prone to publication bias that occurs when positive or significant results are preferred for publication.[ 43 ] Song maintains that studies reporting a certain direction of results or powerful correlations may be more likely to be published than the studies which do not.[ 44 ] In addition, when searching for meta-analyses, gray literature (e.g., dissertations, conference abstracts, or book chapters) and unpublished studies may be missed. Moreover, meta-analyses only based on published studies may exaggerate the estimates of effect sizes; as a result, patients may be exposed to harmful or ineffective treatment methods.[ 44 , 45 ] However, there are some tests that can help in detecting negative expected results that are not included in a review due to publication bias.[ 46 ] In addition, publication bias can be reduced through searching for data that are not published.

Systematic reviews and meta-analyses have certain advantages; some of the most important ones are as follows: examining differences in the findings of different studies, summarizing results from various studies, increased accuracy of estimating effects, increased statistical power, overcoming problems related to small sample sizes, resolving controversies from disagreeing studies, increased generalizability of results, determining the possible need for new studies, overcoming the limitations of narrative reviews, and making new hypotheses for further research.[ 47 , 48 ]

Despite the importance of systematic reviews, the author may face numerous problems in searching, screening, and synthesizing data during this process. A systematic review requires extensive access to databases and journals that can be costly for nonacademic researchers.[ 13 ] Also, in reviewing the inclusion and exclusion criteria, the inevitable mindsets of browsers may be involved and the criteria are interpreted differently from each other.[ 49 ] Lee refers to some disadvantages of these studies, the most significant ones are as follows: a research field cannot be summarized by one number, publication bias, heterogeneity, combining unrelated things, being vulnerable to subjectivity, failing to account for all confounders, comparing variables that are not comparable, just focusing on main effects, and possible inconsistency with results of randomized trials.[ 47 ] Different types of programs are available to perform meta-analysis. Some of the most commonly used statistical programs are general statistical packages, including SAS, SPSS, R, and Stata. Using flexible commands in these programs, meta-analyses can be easily run and the results can be readily plotted out. However, these statistical programs are often expensive. An alternative to using statistical packages is to use programs designed for meta-analysis, including Metawin, RevMan, and Comprehensive Meta-analysis. However, these programs may have limitations, including that they can accept few data formats and do not provide much opportunity to set the graphical display of findings. Another alternative is to use Microsoft Excel. Although it is not a free software, it is usually found in many computers.[ 20 , 50 ]

A systematic review study is a powerful and valuable tool for answering research questions, generating new hypotheses, and identifying areas where there is a lack of tangible knowledge. A systematic review study provides an excellent opportunity for researchers to improve critical assessment and evidence synthesis skills.

Authors' contributions

All authors contributed equally to this work.

Financial support and sponsorship

Conflicts of interest.

There are no conflicts of interest.

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• Systematic Review | Definition, Examples & Guide

Systematic Review | Definition, Examples & Guide

Published on 15 June 2022 by Shaun Turney . Revised on 17 October 2022.

A systematic review is a type of review that uses repeatable methods to find, select, and synthesise all available evidence. It answers a clearly formulated research question and explicitly states the methods used to arrive at the answer.

They answered the question ‘What is the effectiveness of probiotics in reducing eczema symptoms and improving quality of life in patients with eczema?’

In this context, a probiotic is a health product that contains live microorganisms and is taken by mouth. Eczema is a common skin condition that causes red, itchy skin.

Table of contents

What is a systematic review, systematic review vs meta-analysis, systematic review vs literature review, systematic review vs scoping review, when to conduct a systematic review, pros and cons of systematic reviews, step-by-step example of a systematic review, frequently asked questions about systematic reviews.

A review is an overview of the research that’s already been completed on a topic.

What makes a systematic review different from other types of reviews is that the research methods are designed to reduce research bias . The methods are repeatable , and the approach is formal and systematic:

• Formulate a research question
• Develop a protocol
• Search for all relevant studies
• Apply the selection criteria
• Extract the data
• Synthesise the data
• Write and publish a report

Although multiple sets of guidelines exist, the Cochrane Handbook for Systematic Reviews is among the most widely used. It provides detailed guidelines on how to complete each step of the systematic review process.

Systematic reviews are most commonly used in medical and public health research, but they can also be found in other disciplines.

Systematic reviews typically answer their research question by synthesising all available evidence and evaluating the quality of the evidence. Synthesising means bringing together different information to tell a single, cohesive story. The synthesis can be narrative ( qualitative ), quantitative , or both.

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Systematic reviews often quantitatively synthesise the evidence using a meta-analysis . A meta-analysis is a statistical analysis, not a type of review.

A meta-analysis is a technique to synthesise results from multiple studies. It’s a statistical analysis that combines the results of two or more studies, usually to estimate an effect size .

A literature review is a type of review that uses a less systematic and formal approach than a systematic review. Typically, an expert in a topic will qualitatively summarise and evaluate previous work, without using a formal, explicit method.

Although literature reviews are often less time-consuming and can be insightful or helpful, they have a higher risk of bias and are less transparent than systematic reviews.

Similar to a systematic review, a scoping review is a type of review that tries to minimise bias by using transparent and repeatable methods.

However, a scoping review isn’t a type of systematic review. The most important difference is the goal: rather than answering a specific question, a scoping review explores a topic. The researcher tries to identify the main concepts, theories, and evidence, as well as gaps in the current research.

Sometimes scoping reviews are an exploratory preparation step for a systematic review, and sometimes they are a standalone project.

A systematic review is a good choice of review if you want to answer a question about the effectiveness of an intervention , such as a medical treatment.

To conduct a systematic review, you’ll need the following:

• A precise question , usually about the effectiveness of an intervention. The question needs to be about a topic that’s previously been studied by multiple researchers. If there’s no previous research, there’s nothing to review.
• If you’re doing a systematic review on your own (e.g., for a research paper or thesis), you should take appropriate measures to ensure the validity and reliability of your research.
• Access to databases and journal archives. Often, your educational institution provides you with access.
• Time. A professional systematic review is a time-consuming process: it will take the lead author about six months of full-time work. If you’re a student, you should narrow the scope of your systematic review and stick to a tight schedule.
• Bibliographic, word-processing, spreadsheet, and statistical software . For example, you could use EndNote, Microsoft Word, Excel, and SPSS.

A systematic review has many pros .

• They minimise research b ias by considering all available evidence and evaluating each study for bias.
• Their methods are transparent , so they can be scrutinised by others.
• They’re thorough : they summarise all available evidence.
• They can be replicated and updated by others.

Systematic reviews also have a few cons .

• They’re time-consuming .
• They’re narrow in scope : they only answer the precise research question.

The 7 steps for conducting a systematic review are explained with an example.

Step 1: Formulate a research question

Formulating the research question is probably the most important step of a systematic review. A clear research question will:

• Allow you to more effectively communicate your research to other researchers and practitioners
• Guide your decisions as you plan and conduct your systematic review

A good research question for a systematic review has four components, which you can remember with the acronym PICO :

• Population(s) or problem(s)
• Intervention(s)
• Comparison(s)

You can rearrange these four components to write your research question:

• What is the effectiveness of I versus C for O in P ?

Sometimes, you may want to include a fourth component, the type of study design . In this case, the acronym is PICOT .

• Type of study design(s)
• The population of patients with eczema
• The intervention of probiotics
• In comparison to no treatment, placebo , or non-probiotic treatment
• The outcome of changes in participant-, parent-, and doctor-rated symptoms of eczema and quality of life
• Randomised control trials, a type of study design

Their research question was:

• What is the effectiveness of probiotics versus no treatment, a placebo, or a non-probiotic treatment for reducing eczema symptoms and improving quality of life in patients with eczema?

Step 2: Develop a protocol

A protocol is a document that contains your research plan for the systematic review. This is an important step because having a plan allows you to work more efficiently and reduces bias.

Your protocol should include the following components:

• Background information : Provide the context of the research question, including why it’s important.
• Research objective(s) : Rephrase your research question as an objective.
• Selection criteria: State how you’ll decide which studies to include or exclude from your review.
• Search strategy: Discuss your plan for finding studies.
• Analysis: Explain what information you’ll collect from the studies and how you’ll synthesise the data.

If you’re a professional seeking to publish your review, it’s a good idea to bring together an advisory committee . This is a group of about six people who have experience in the topic you’re researching. They can help you make decisions about your protocol.

It’s highly recommended to register your protocol. Registering your protocol means submitting it to a database such as PROSPERO or ClinicalTrials.gov .

Step 3: Search for all relevant studies

Searching for relevant studies is the most time-consuming step of a systematic review.

To reduce bias, it’s important to search for relevant studies very thoroughly. Your strategy will depend on your field and your research question, but sources generally fall into these four categories:

• Databases: Search multiple databases of peer-reviewed literature, such as PubMed or Scopus . Think carefully about how to phrase your search terms and include multiple synonyms of each word. Use Boolean operators if relevant.
• Handsearching: In addition to searching the primary sources using databases, you’ll also need to search manually. One strategy is to scan relevant journals or conference proceedings. Another strategy is to scan the reference lists of relevant studies.
• Grey literature: Grey literature includes documents produced by governments, universities, and other institutions that aren’t published by traditional publishers. Graduate student theses are an important type of grey literature, which you can search using the Networked Digital Library of Theses and Dissertations (NDLTD) . In medicine, clinical trial registries are another important type of grey literature.
• Experts: Contact experts in the field to ask if they have unpublished studies that should be included in your review.

At this stage of your review, you won’t read the articles yet. Simply save any potentially relevant citations using bibliographic software, such as Scribbr’s APA or MLA Generator .

• Databases: EMBASE, PsycINFO, AMED, LILACS, and ISI Web of Science
• Handsearch: Conference proceedings and reference lists of articles
• Grey literature: The Cochrane Library, the metaRegister of Controlled Trials, and the Ongoing Skin Trials Register
• Experts: Authors of unpublished registered trials, pharmaceutical companies, and manufacturers of probiotics

Step 4: Apply the selection criteria

Applying the selection criteria is a three-person job. Two of you will independently read the studies and decide which to include in your review based on the selection criteria you established in your protocol . The third person’s job is to break any ties.

To increase inter-rater reliability , ensure that everyone thoroughly understands the selection criteria before you begin.

If you’re writing a systematic review as a student for an assignment, you might not have a team. In this case, you’ll have to apply the selection criteria on your own; you can mention this as a limitation in your paper’s discussion.

You should apply the selection criteria in two phases:

• Based on the titles and abstracts : Decide whether each article potentially meets the selection criteria based on the information provided in the abstracts.
• Based on the full texts: Download the articles that weren’t excluded during the first phase. If an article isn’t available online or through your library, you may need to contact the authors to ask for a copy. Read the articles and decide which articles meet the selection criteria.

It’s very important to keep a meticulous record of why you included or excluded each article. When the selection process is complete, you can summarise what you did using a PRISMA flow diagram .

Next, Boyle and colleagues found the full texts for each of the remaining studies. Boyle and Tang read through the articles to decide if any more studies needed to be excluded based on the selection criteria.

When Boyle and Tang disagreed about whether a study should be excluded, they discussed it with Varigos until the three researchers came to an agreement.

Step 5: Extract the data

Extracting the data means collecting information from the selected studies in a systematic way. There are two types of information you need to collect from each study:

• Information about the study’s methods and results . The exact information will depend on your research question, but it might include the year, study design , sample size, context, research findings , and conclusions. If any data are missing, you’ll need to contact the study’s authors.
• Your judgement of the quality of the evidence, including risk of bias .

You should collect this information using forms. You can find sample forms in The Registry of Methods and Tools for Evidence-Informed Decision Making and the Grading of Recommendations, Assessment, Development and Evaluations Working Group .

Extracting the data is also a three-person job. Two people should do this step independently, and the third person will resolve any disagreements.

They also collected data about possible sources of bias, such as how the study participants were randomised into the control and treatment groups.

Step 6: Synthesise the data

Synthesising the data means bringing together the information you collected into a single, cohesive story. There are two main approaches to synthesising the data:

• Narrative ( qualitative ): Summarise the information in words. You’ll need to discuss the studies and assess their overall quality.
• Quantitative : Use statistical methods to summarise and compare data from different studies. The most common quantitative approach is a meta-analysis , which allows you to combine results from multiple studies into a summary result.

Generally, you should use both approaches together whenever possible. If you don’t have enough data, or the data from different studies aren’t comparable, then you can take just a narrative approach. However, you should justify why a quantitative approach wasn’t possible.

Boyle and colleagues also divided the studies into subgroups, such as studies about babies, children, and adults, and analysed the effect sizes within each group.

Step 7: Write and publish a report

The purpose of writing a systematic review article is to share the answer to your research question and explain how you arrived at this answer.

Your article should include the following sections:

• Abstract : A summary of the review
• Introduction : Including the rationale and objectives
• Methods : Including the selection criteria, search method, data extraction method, and synthesis method
• Results : Including results of the search and selection process, study characteristics, risk of bias in the studies, and synthesis results
• Discussion : Including interpretation of the results and limitations of the review
• Conclusion : The answer to your research question and implications for practice, policy, or research

To verify that your report includes everything it needs, you can use the PRISMA checklist .

Once your report is written, you can publish it in a systematic review database, such as the Cochrane Database of Systematic Reviews , and/or in a peer-reviewed journal.

A systematic review is secondary research because it uses existing research. You don’t collect new data yourself.

A literature review is a survey of scholarly sources (such as books, journal articles, and theses) related to a specific topic or research question .

It is often written as part of a dissertation , thesis, research paper , or proposal .

There are several reasons to conduct a literature review at the beginning of a research project:

• To familiarise yourself with the current state of knowledge on your topic
• To ensure that you’re not just repeating what others have already done
• To identify gaps in knowledge and unresolved problems that your research can address
• To develop your theoretical framework and methodology
• To provide an overview of the key findings and debates on the topic

Writing the literature review shows your reader how your work relates to existing research and what new insights it will contribute.

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Conducting a Systematic Review: A Practical Guide

• Reference work entry
• First Online: 13 January 2019
• Cite this reference work entry

• Freya MacMillan 2 ,
• Kate A. McBride 3 ,
• Emma S. George 4 &
• Genevieve Z. Steiner 5  

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It can be challenging to conduct a systematic review with limited experience and skills in undertaking such a task. This chapter provides a practical guide to undertaking a systematic review, providing step-by-step instructions to guide the individual through the process from start to finish. The chapter begins with defining what a systematic review is, reviewing its various components, turning a research question into a search strategy, developing a systematic review protocol, followed by searching for relevant literature and managing citations. Next, the chapter focuses on documenting the characteristics of included studies and summarizing findings, extracting data, methods for assessing risk of bias and considering heterogeneity, and undertaking meta-analyses. Last, the chapter explores creating a narrative and interpreting findings. Practical tips and examples from existing literature are utilized throughout the chapter to assist readers in their learning. By the end of this chapter, the reader will have the knowledge to conduct their own systematic review.

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MacMillan, F., McBride, K.A., George, E.S., Steiner, G.Z. (2019). Conducting a Systematic Review: A Practical Guide. In: Liamputtong, P. (eds) Handbook of Research Methods in Health Social Sciences. Springer, Singapore. https://doi.org/10.1007/978-981-10-5251-4_113

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Systematic review Q & A

What is a systematic review.

A systematic review is guided filtering and synthesis of all available evidence addressing a specific, focused research question, generally about a specific intervention or exposure. The use of standardized, systematic methods and pre-selected eligibility criteria reduce the risk of bias in identifying, selecting and analyzing relevant studies. A well-designed systematic review includes clear objectives, pre-selected criteria for identifying eligible studies, an explicit methodology, a thorough and reproducible search of the literature, an assessment of the validity or risk of bias of each included study, and a systematic synthesis, analysis and presentation of the findings of the included studies. A systematic review may include a meta-analysis.

For details about carrying out systematic reviews, see the Guides and Standards section of this guide.

Is my research topic appropriate for systematic review methods?

A systematic review is best deployed to test a specific hypothesis about a healthcare or public health intervention or exposure. By focusing on a single intervention or a few specific interventions for a particular condition, the investigator can ensure a manageable results set. Moreover, examining a single or small set of related interventions, exposures, or outcomes, will simplify the assessment of studies and the synthesis of the findings.

Systematic reviews are poor tools for hypothesis generation: for instance, to determine what interventions have been used to increase the awareness and acceptability of a vaccine or to investigate the ways that predictive analytics have been used in health care management. In the first case, we don't know what interventions to search for and so have to screen all the articles about awareness and acceptability. In the second, there is no agreed on set of methods that make up predictive analytics, and health care management is far too broad. The search will necessarily be incomplete, vague and very large all at the same time. In most cases, reviews without clearly and exactly specified populations, interventions, exposures, and outcomes will produce results sets that quickly outstrip the resources of a small team and offer no consistent way to assess and synthesize findings from the studies that are identified.

If not a systematic review, then what?

You might consider performing a scoping review . This framework allows iterative searching over a reduced number of data sources and no requirement to assess individual studies for risk of bias. The framework includes built-in mechanisms to adjust the analysis as the work progresses and more is learned about the topic. A scoping review won't help you limit the number of records you'll need to screen (broad questions lead to large results sets) but may give you means of dealing with a large set of results.

This tool can help you decide what kind of review is right for your question.

Can my student complete a systematic review during her summer project?

Probably not. Systematic reviews are a lot of work. Including creating the protocol, building and running a quality search, collecting all the papers, evaluating the studies that meet the inclusion criteria and extracting and analyzing the summary data, a well done review can require dozens to hundreds of hours of work that can span several months. Moreover, a systematic review requires subject expertise, statistical support and a librarian to help design and run the search. Be aware that librarians sometimes have queues for their search time. It may take several weeks to complete and run a search. Moreover, all guidelines for carrying out systematic reviews recommend that at least two subject experts screen the studies identified in the search. The first round of screening can consume 1 hour per screener for every 100-200 records. A systematic review is a labor-intensive team effort.

How can I know if my topic has been been reviewed already?

Before starting out on a systematic review, check to see if someone has done it already. In PubMed you can use the systematic review subset to limit to a broad group of papers that is enriched for systematic reviews. You can invoke the subset by selecting if from the Article Types filters to the left of your PubMed results, or you can append AND systematic[sb] to your search. For example:

"neoadjuvant chemotherapy" AND systematic[sb]

The systematic review subset is very noisy, however. To quickly focus on systematic reviews (knowing that you may be missing some), simply search for the word systematic in the title:

"neoadjuvant chemotherapy" AND systematic[ti]

Any PRISMA-compliant systematic review will be captured by this method since including the words "systematic review" in the title is a requirement of the PRISMA checklist. Cochrane systematic reviews do not include 'systematic' in the title, however. It's worth checking the Cochrane Database of Systematic Reviews independently.

You can also search for protocols that will indicate that another group has set out on a similar project. Many investigators will register their protocols in PROSPERO , a registry of review protocols. Other published protocols as well as Cochrane Review protocols appear in the Cochrane Methodology Register, a part of the Cochrane Library .

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What is a Systematic Review?

A systematic review gathers, assesses, and synthesizes  all available empirical  research on a specific question using a comprehensive search method with an aim to minimize bias.

Or, put another way : 

A systematic review begins with a specific research question.  Authors of the review gather and evaluate all experimental studies that address the question .  Bringing together the findings of these separate studies allows the review authors to make new conclusions from what has been learned.

*The key characteristics of a systematic review are:

• A clearly stated set of objectives with pre-defined eligibility criteria for studies;
• An explicit, reproducible methodology;
• A systematic search that attempts to identify all relevant research;
• A critical appraisal of the included studies;
• A clear and objective synthesis and presentation of the characteristics and findings of the included studies.

*Lasserson T, Thomas J, Higgins JPT. Chapter 1: Starting a review. In Higgins JPT, Thomas J, Chandler J, Cumpston M, Li T, Page MJ, Welch VA (editors).  Cochrane Handbook for Systematic Reviews of Interventions  version 6.4 (updated August 2023). Cochrane, 2023. Available from www.training.cochrane.org/handbook .

What is the difference between an evidence synthesis and a systematic review? A systematic review is a type of evidence synthesis.  Any literature review is a type of evidence synthesis.  For the various types of evidence syntheses/literature reviews, see the page on this guide Types of Reviews .

Systematic reviews are usually done as a team project , requiring cooperation and a commitment of (lots of) time and effort over an extended period. You will need at least 3 people and, depending on the scope of the project and the size of the database result sets, you should plan for 6-24 months from start to completion

Things to Know Before You Begin . . .

Run exploratory searches on the topic to get a sense of the plausibility of your project.

A systematic review requires a research question that is already well-covered in the primary literature.  That is, if there has been little previous work on the topic, there will be little to analyze and conclusions hard to find.

A narrowly-focused research question may add little to the knowledge of the field of study.

Make sure someone else has not already 1) written a recent systematic review on your topic, or 2) is in the midst of a similar systematic review project. Instructions on how to check .

Team members will need to use research databases for searching the literature.  If these databases are not available through library subscriptions or freely available, their use may require payment or travel. Look here for database recommendations .

It is extremely important to develop a protocol for your project.  Guidance is provided here .

Tools such as a reference manager and a screening tool will save time.  

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Easy guide to conducting a systematic review

Affiliations.

• 1 Discipline of Child and Adolescent Health, University of Sydney, Sydney, New South Wales, Australia.
• 2 Department of Nephrology, The Children's Hospital at Westmead, Sydney, New South Wales, Australia.
• 3 Education Department, The Children's Hospital at Westmead, Sydney, New South Wales, Australia.
• PMID: 32364273
• DOI: 10.1111/jpc.14853

A systematic review is a type of study that synthesises research that has been conducted on a particular topic. Systematic reviews are considered to provide the highest level of evidence on the hierarchy of evidence pyramid. Systematic reviews are conducted following rigorous research methodology. To minimise bias, systematic reviews utilise a predefined search strategy to identify and appraise all available published literature on a specific topic. The meticulous nature of the systematic review research methodology differentiates a systematic review from a narrative review (literature review or authoritative review). This paper provides a brief step by step summary of how to conduct a systematic review, which may be of interest for clinicians and researchers.

Keywords: research; research design; systematic review.

© 2020 Paediatrics and Child Health Division (The Royal Australasian College of Physicians).

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"A systematic review attempts to collate all empirical evidence that fits pre-specified eligibility criteria in order to answer a specific research question.  It  uses explicit, systematic methods that are selected with a view to minimizing bias, thus providing more reliable findings from which conclusions can be drawn and decisions made   (Antman 1992, Oxman 1993) . The key characteristics of a systematic review are:

a clearly stated set of objectives with pre-defined eligibility criteria for studies;

an explicit, reproducible methodology;

a systematic search that attempts to identify all studies that would meet the eligibility criteria;

an assessment of the validity of the findings of the included studies, for example through the assessment of risk of bias; and

a systematic presentation, and synthesis, of the characteristics and findings of the included studies".

Cochrane Handbook for Systematic Reviews of Interventions . (March 2011)

(Original author, Meredith Kirkpatrick, 2021)

Kysh, Lynn (2013): Difference between a systematic review and a literature review . Figshare.https://doi.org/10.6084/m9.figshare.766364.v1  

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Answered By: Kate Krause Last Updated: Aug 03, 2022     Views: 134

Systematic reviews gather ALL the relevant studies that have already been conducted on a specific clinical question.

They evaluate the studies, select the best ones, and synthesize their findings.

If they have found enough good quality studies, systematic reviews give clinical recommendations. 

Systematic reviews follow a structured research process that requires rigorous methods to ensure that the results are reliable. This is why they're considered to be one of the highest forms of evidence-based medicine. 

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Related Topics

• Systematic Reviews

Systematic Review

• Library Help
• What is a Systematic Review (SR)?
• Steps of a Systematic Review
• Framing a Research Question
• Developing a Search Strategy
• Searching the Literature
• Managing the Process
• Meta-analysis
• Publishing your Systematic Review

Introduction to Systematic Review

• Introduction
• Types of literature reviews
• Other Libguides
• Systematic review as part of a dissertation
• Tutorials & Guidelines & Examples from non-Medical Disciplines

Depending on your learning style, please explore the resources in various formats on the tabs above.

For additional tutorials, visit the SR Workshop Videos  from UNC at Chapel Hill outlining each stage of the systematic review process.

Know the difference! Systematic review vs. literature review

Types of literature reviews along with associated methodologies

JBI Manual for Evidence Synthesis .  Find definitions and methodological guidance.

- Systematic Reviews - Chapters 1-7

- Mixed Methods Systematic Reviews -  Chapter 8

- Diagnostic Test Accuracy Systematic Reviews -  Chapter 9

- Umbrella Reviews -  Chapter 10

- Scoping Reviews -  Chapter 11

- Systematic Reviews of Measurement Properties -  Chapter 12

Systematic reviews vs scoping reviews - 

Grant, M. J., & Booth, A. (2009). A typology of reviews: an analysis of 14 review types and associated methodologies. Health Information and Libraries Journal , 26 (2), 91–108. https://doi.org/10.1111/j.1471-1842.2009.00848.x

Gough, D., Thomas, J., & Oliver, S. (2012). Clarifying differences between review designs and methods. Systematic Reviews, 1 (28). htt p s://doi.org/ 10.1186/2046-4053-1-28

Munn, Z., Peters, M., Stern, C., Tufanaru, C., McArthur, A., & Aromataris, E. (2018).  Systematic review or  scoping review ?  Guidance for authors when choosing between a systematic or scoping review approach.  BMC medical research methodology, 18 (1), 143. https://doi.org/10.1186/s12874-018-0611-x. Also, check out the  Libguide from Weill Cornell Medicine  for the  differences between a systematic review and a scoping review  and when to embark on either one of them.

Sutton, A., Clowes, M., Preston, L., & Booth, A. (2019). Meeting the review family: Exploring review types and associated information retrieval requirements . Health Information & Libraries Journal , 36 (3), 202–222. https://doi.org/10.1111/hir.12276

Temple University. Review Types . - This guide provides useful descriptions of some of the types of reviews listed in the above article.

UMD Health Sciences and Human Services Library.  Review Types . - Guide describing Literature Reviews, Scoping Reviews, and Rapid Reviews.

Whittemore, R., Chao, A., Jang, M., Minges, K. E., & Park, C. (2014). Methods for knowledge synthesis: An overview. Heart & Lung: The Journal of Acute and Critical Care, 43 (5), 453–461. https://doi.org/10.1016/j.hrtlng.2014.05.014

Differences between a systematic review and other types of reviews

Armstrong, R., Hall, B. J., Doyle, J., & Waters, E. (2011). ‘ Scoping the scope ’ of a cochrane review. Journal of Public Health , 33 (1), 147–150. https://doi.org/10.1093/pubmed/fdr015

Kowalczyk, N., & Truluck, C. (2013). Literature reviews and systematic reviews: What is the difference? Radiologic Technology , 85 (2), 219–222.

White, H., Albers, B., Gaarder, M., Kornør, H., Littell, J., Marshall, Z., Matthew, C., Pigott, T., Snilstveit, B., Waddington, H., & Welch, V. (2020). Guidance for producing a Campbell evidence and gap map . Campbell Systematic Reviews, 16 (4), e1125. https://doi.org/10.1002/cl2.1125. Check also this comparison between evidence and gaps maps and systematic reviews.

Rapid Reviews Tutorials

Rapid Review Guidebook  by the National Collaborating Centre of Methods and Tools (NCCMT)

Hamel, C., Michaud, A., Thuku, M., Skidmore, B., Stevens, A., Nussbaumer-Streit, B., & Garritty, C. (2021). Defining Rapid Reviews: a systematic scoping review and thematic analysis of definitions and defining characteristics of rapid reviews.  Journal of clinical epidemiology ,  129 , 74–85. https://doi.org/10.1016/j.jclinepi.2020.09.041

• Müller, C., Lautenschläger, S., Meyer, G., & Stephan, A. (2017). Interventions to support people with dementia and their caregivers during the transition from home care to nursing home care: A systematic review . International Journal of Nursing Studies, 71 , 139–152. https://doi.org/10.1016/j.ijnurstu.2017.03.013
• Bhui, K. S., Aslam, R. W., Palinski, A., McCabe, R., Johnson, M. R. D., Weich, S., … Szczepura, A. (2015). Interventions to improve therapeutic communications between Black and minority ethnic patients and professionals in psychiatric services: Systematic review . The British Journal of Psychiatry, 207 (2), 95–103. https://doi.org/10.1192/bjp.bp.114.158899
• Rosen, L. J., Noach, M. B., Winickoff, J. P., & Hovell, M. F. (2012). Parental smoking cessation to protect young children: A systematic review and meta-analysis . Pediatrics, 129 (1), 141–152. https://doi.org/10.1542/peds.2010-3209

Scoping Review

• Hyshka, E., Karekezi, K., Tan, B., Slater, L. G., Jahrig, J., & Wild, T. C. (2017). The role of consumer perspectives in estimating population need for substance use services: A scoping review . BMC Health Services Research, 171-14.  https://doi.org/10.1186/s12913-017-2153-z
• Olson, K., Hewit, J., Slater, L.G., Chambers, T., Hicks, D., Farmer, A., & ... Kolb, B. (2016). Assessing cognitive function in adults during or following chemotherapy: A scoping review . Supportive Care In Cancer, 24 (7), 3223-3234. https://doi.org/10.1007/s00520-016-3215-1
• Pham, M. T., Rajić, A., Greig, J. D., Sargeant, J. M., Papadopoulos, A., & McEwen, S. A. (2014). A scoping review of scoping reviews: Advancing the approach and enhancing the consistency . Research Synthesis Methods, 5 (4), 371–385. https://doi.org/10.1002/jrsm.1123
• Scoping Review Tutorial from UNC at Chapel Hill

Qualitative Systematic Review/Meta-Synthesis

• Lee, H., Tamminen, K. A., Clark, A. M., Slater, L., Spence, J. C., & Holt, N. L. (2015). A meta-study of qualitative research examining determinants of children's independent active free play . International Journal Of Behavioral Nutrition & Physical Activity, 12 (5), 121-12. https://doi.org/10.1186/s12966-015-0165-9

Videos on systematic reviews

Systematic Reviews: What are they? Are they right for my research? - 47 min. video recording with a closed caption option.

More training videos  on systematic reviews:   

Books on Systematic Reviews

Books on Meta-analysis

• University of Toronto Libraries  - very detailed with good tips on the sensitivity and specificity of searches.
• Monash University  - includes an interactive case study tutorial. 
• Dalhousie University Libraries - a comprehensive How-To Guide on conducting a systematic review.

Guidelines for a systematic review as part of the dissertation

• Guidelines for Systematic Reviews in the Context of Doctoral Education Background  by University of Victoria (PDF)
• Can I conduct a Systematic Review as my Master’s dissertation or PhD thesis? Yes, It Depends!  by Farhad (blog)
• What is a Systematic Review Dissertation Like? by the University of Edinburgh (50 min video) 

Further readings on experiences of PhD students and doctoral programs with systematic reviews

Puljak, L., & Sapunar, D. (2017). Acceptance of a systematic review as a thesis: Survey of biomedical doctoral programs in Europe . Systematic Reviews , 6 (1), 253. https://doi.org/10.1186/s13643-017-0653-x

Perry, A., & Hammond, N. (2002). Systematic reviews: The experiences of a PhD Student . Psychology Learning & Teaching , 2 (1), 32–35. https://doi.org/10.2304/plat.2002.2.1.32

Daigneault, P.-M., Jacob, S., & Ouimet, M. (2014). Using systematic review methods within a Ph.D. dissertation in political science: Challenges and lessons learned from practice . International Journal of Social Research Methodology , 17 (3), 267–283. https://doi.org/10.1080/13645579.2012.730704

UMD Doctor of Philosophy Degree Policies

Before you embark on a systematic review research project, check the UMD PhD Policies to make sure you are on the right path. Systematic reviews require a team of at least two reviewers and an information specialist or a librarian. Discuss with your advisor the authorship roles of the involved team members. Keep in mind that the  UMD Doctor of Philosophy Degree Policies (scroll down to the section, Inclusion of one's own previously published materials in a dissertation ) outline such cases, specifically the following: 

" It is recognized that a graduate student may co-author work with faculty members and colleagues that should be included in a dissertation . In such an event, a letter should be sent to the Dean of the Graduate School certifying that the student's examining committee has determined that the student made a substantial contribution to that work. This letter should also note that the inclusion of the work has the approval of the dissertation advisor and the program chair or Graduate Director. The letter should be included with the dissertation at the time of submission.  The format of such inclusions must conform to the standard dissertation format. A foreword to the dissertation, as approved by the Dissertation Committee, must state that the student made substantial contributions to the relevant aspects of the jointly authored work included in the dissertation."

• Cochrane Handbook for Systematic Reviews of Interventions - See Part 2: General methods for Cochrane reviews
• Systematic Searches - Yale library video tutorial series 
• Using PubMed's Clinical Queries to Find Systematic Reviews  - From the U.S. National Library of Medicine
• Systematic reviews and meta-analyses: A step-by-step guide - From the University of Edinsburgh, Centre for Cognitive Ageing and Cognitive Epidemiology

Bioinformatics

• Mariano, D. C., Leite, C., Santos, L. H., Rocha, R. E., & de Melo-Minardi, R. C. (2017). A guide to performing systematic literature reviews in bioinformatics .  arXiv preprint arXiv:1707.05813.

Environmental Sciences

Collaboration for Environmental Evidence. 2018.  Guidelines and Standards for Evidence synthesis in Environmental Management. Version 5.0 (AS Pullin, GK Frampton, B Livoreil & G Petrokofsky, Eds) www.environmentalevidence.org/information-for-authors .

Pullin, A. S., & Stewart, G. B. (2006). Guidelines for systematic review in conservation and environmental management. Conservation Biology, 20 (6), 1647–1656. https://doi.org/10.1111/j.1523-1739.2006.00485.x

Engineering Education

• Borrego, M., Foster, M. J., & Froyd, J. E. (2014). Systematic literature reviews in engineering education and other developing interdisciplinary fields. Journal of Engineering Education, 103 (1), 45–76. https://doi.org/10.1002/jee.20038

Public Health

• Hannes, K., & Claes, L. (2007). Learn to read and write systematic reviews: The Belgian Campbell Group . Research on Social Work Practice, 17 (6), 748–753. https://doi.org/10.1177/1049731507303106
• McLeroy, K. R., Northridge, M. E., Balcazar, H., Greenberg, M. R., & Landers, S. J. (2012). Reporting guidelines and the American Journal of Public Health’s adoption of preferred reporting items for systematic reviews and meta-analyses . American Journal of Public Health, 102 (5), 780–784. https://doi.org/10.2105/AJPH.2011.300630
• Pollock, A., & Berge, E. (2018). How to do a systematic review.   International Journal of Stroke, 13 (2), 138–156. https://doi.org/10.1177/1747493017743796
• Institute of Medicine. (2011). Finding what works in health care: Standards for systematic reviews . https://doi.org/10.17226/13059
• Wanden-Berghe, C., & Sanz-Valero, J. (2012). Systematic reviews in nutrition: Standardized methodology . The British Journal of Nutrition, 107 Suppl 2, S3-7. https://doi.org/10.1017/S0007114512001432

Social Sciences

• Bronson, D., & Davis, T. (2012).  Finding and evaluating evidence: Systematic reviews and evidence-based practice (Pocket guides to social work research methods). Oxford: Oxford University Press.
• Petticrew, M., & Roberts, H. (2006).  Systematic reviews in the social sciences: A practical guide . Malden, MA: Blackwell Pub.
• Cornell University Library Guide -  Systematic literature reviews in engineering: Example: Software Engineering
• Biolchini, J., Mian, P. G., Natali, A. C. C., & Travassos, G. H. (2005). Systematic review in software engineering .  System Engineering and Computer Science Department COPPE/UFRJ, Technical Report ES, 679 (05), 45.
• Biolchini, J. C., Mian, P. G., Natali, A. C. C., Conte, T. U., & Travassos, G. H. (2007). Scientific research ontology to support systematic review in software engineering . Advanced Engineering Informatics, 21 (2), 133–151.
• Kitchenham, B. (2007). Guidelines for performing systematic literature reviews in software engineering . [Technical Report]. Keele, UK, Keele University, 33(2004), 1-26.
• Weidt, F., & Silva, R. (2016). Systematic literature review in computer science: A practical guide .  Relatórios Técnicos do DCC/UFJF ,  1 .
• Academic Phrasebank - Get some inspiration and find some terms and phrases for writing your research paper
• Oxford English Dictionary  - Use to locate word variants and proper spelling
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Systematic Review Process: Screening and Study Selection

• Definitions of a Systematic Review
• Types of Reviews
• Systematic Review Planning Process
• Resources Needed to Conduct a Review
• Reporting Guidelines
• Where to Search
• How to Search
• Screening and Study Selection
• Data Extraction
• Appraisal and Analysis
• Citation Management
• Additional Resources: Guides and Books
• Using Covidence for Your Systematic Review
• Librarian Collaboration

Screening for Studies

Searching for studies is different than  screening  for studies. When screening potential articles to be included in a knowledge synthesis, keep these pointers in mind:

• Think specifically, and at a granular level
• Decisions are based on the specific characteristics of each study, as defined by the scope of your topic, and that will answer your question, eligibility criteria should be consistent with these characteristics
• The process on how to handle uncertainty when screening should also be pre-determined, e.g. if the study is missing data, then include for now
• Reviewers should have a high minimum of 90% agreement among them in their screening process

Content reused with permission from the University of Toronto Libraries

Levels of Screening

Piloting the Screening Process

At every stage of screening, the screening process should be tested out to check what works and doesn't work for your specific team for this specific review. A small sample of all the articles to be screened are used to pilot a screening method and feedback from the reviewers are used to revise the screening method (inclusion/exclusion criteria details and definitions). This cycles until an agreeable method is found which then can be applied to the remaining articles.

First Level of Screening

In the first stage of screening, a pair of reviewers from the review team will  independently  scan titles and abstracts of articles that were retrieved from a comprehensive (i.e., multiple source) search, and make decisions whether to  include  or  exclude  articles. To do this in a streamlined, unbiased, and method-driven way, reviewers should adhere to the pre-defined eligibility criteria, or guidance form.

Keep these tips in mind during the first stage of screening:

• Authors should generally be over-inclusive at this stage; a maybe is always a yes at this point
• Screen for outcomes with caution if at all; they're poorly reported in the title and abstract. Save those for full-text!
• Ask yourself: Is there enough information in the title and abstract to exclude this study at this stage, with absolute certainty?

Second Level of Screening

The second level of screening is a more rigorous, in-depth process in which the articles that were included in the first stage of screening are read in full-text. Similar to the first level of screening, this is done independently by two reviewers from the review team, and the eligibility criteria that was used as a guideline for the first level of screening is largely the same. However, the second level of screening differs in these important ways:

• The reason(s) for exclusion must be recorded and reported
• You can now screen for outcome(s). Ask yourself: does the study report on the outcome(s) you're interested in?
• Although the eligibility criteria is the same, it will require additional detail (clarifying questions may arise during the first stage of screening)

Tools for Screening

Tools to help with the screening process.  

Rayyan  is a popular web-based tool for collecting and screening citations. It has options to screen with multiple people, masking each other. Pricing is free to early career researchers and there is reasonable pricing for other users.

Screenatron is part of the  SR Acclerator  suite of tools that may help with the screening process.

Covidence is web-based software platform that streamlines the production of systematic reviews, including Cochrane Reviews. Includes citation screening, full text review, risk of bias assessment, extraction of study characteristics and other study data, export of data into RevMan . Please note that RevMan is Cochrane's custom software for writing Cochrane Reviews. Nonprofit organization, open-source software

You might want to read this article which reviews several screening tools:

Harrison, H., Griffin, S. J., Kuhn, I., & Usher-Smith, J. A. (2020). Software tools to support title and abstract screening for systematic reviews in healthcare: an evaluation.   BMC medical research methodology ,  20 (1), 7.

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