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Systematic Review | Definition, Example & Guide

Published on June 15, 2022 by Shaun Turney . Revised on November 20, 2023.

A systematic review is a type of review that uses repeatable methods to find, select, and synthesize 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, other interesting articles, 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 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
  • Synthesize 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 synthesizing all available evidence and evaluating the quality of the evidence. Synthesizing 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 synthesize 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 synthesize 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 summarize 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 minimize 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.

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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 minimize research bias by considering all available evidence and evaluating each study for bias.
  • Their methods are transparent , so they can be scrutinized by others.
  • They’re thorough : they summarize 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 fifth 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
  • Randomized 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 synthesize 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.
  • Gray literature: Gray 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 gray 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 gray 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
  • Gray 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 summarize 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 judgment 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 randomized into the control and treatment groups.

Step 6: Synthesize the data

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

  • Narrative ( qualitative ): Summarize the information in words. You’ll need to discuss the studies and assess their overall quality.
  • Quantitative : Use statistical methods to summarize 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 analyzed 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.

In their report, Boyle and colleagues concluded that probiotics cannot be recommended for reducing eczema symptoms or improving quality of life in patients with eczema. Note Generative AI tools like ChatGPT can be useful at various stages of the writing and research process and can help you to write your systematic review. However, we strongly advise against trying to pass AI-generated text off as your own work.

If you want to know more about statistics , methodology , or research bias , make sure to check out some of our other articles with explanations and examples.

  • Student’s  t -distribution
  • Normal distribution
  • Null and Alternative Hypotheses
  • Chi square tests
  • Confidence interval
  • Quartiles & Quantiles
  • Cluster sampling
  • Stratified sampling
  • Data cleansing
  • Reproducibility vs Replicability
  • Peer review
  • Prospective cohort study

Research bias

  • Implicit bias
  • Cognitive bias
  • Placebo effect
  • Hawthorne effect
  • Hindsight bias
  • Affect heuristic
  • Social desirability bias

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 thesis, dissertation , or research paper , in order to situate your work in relation to existing knowledge.

A literature review is a survey of credible sources on a topic, often used in dissertations , theses, and research papers . Literature reviews give an overview of knowledge on a subject, helping you identify relevant theories and methods, as well as gaps in existing research. Literature reviews are set up similarly to other  academic texts , with an introduction , a main body, and a conclusion .

An  annotated bibliography is a list of  source references that has a short description (called an annotation ) for each of the sources. It is often assigned as part of the research process for a  paper .  

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

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Systematic Review

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  • 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

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  • PICO Template
  • Inclusion/Exclusion Criteria
  • Database Search Log
  • Review Matrix
  • Cochrane Tool for Assessing Risk of Bias in Included Studies

   • PRISMA Flow Diagram  - Record the numbers of retrieved references and included/excluded studies. You can use the Create Flow Diagram tool to automate the process.

   •  PRISMA Checklist - Checklist of items to include when reporting a systematic review or meta-analysis

PRISMA 2020 and PRISMA-S: Common Questions on Tracking Records and the Flow Diagram

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Systematic reviews: Structure, form and content

This article aims to provide an overview of the structure, form and content of systematic reviews. It focuses in particular on the literature searching component, and covers systematic database searching techniques, searching for grey literature and the importance of librarian involvement in the search. It also covers systematic review reporting standards such as PRISMA-P and PRISMA, critical appraisal and tools and resources to support the review and ensure it is conducted efficiently and effectively. Finally, it summarizes the requirements when screening search results for inclusion in the review, and the statistical synthesis of included studies’ findings.

Provenance and Peer review: Solicited contribution; Peer reviewed; Accepted for publication 24 January 2021.

Introduction

A systematic review collects secondary data, and is a synthesis of all available, relevant evidence which brings together all existing primary studies for review ( Cochrane 2016 ). A systematic review differs from other types of literature review in several major ways. It requires a transparent, reproducible methodology which indicates how studies were identified and the criteria upon which they were included or excluded. As well as synthesis of these studies' findings, there should be an element of evaluation and quality assessment. The systematic review methodology originated in medical and healthcare research, but it has now been adopted by other disciplines, such as engineering, education, economics and business studies. The processes and requirements for conducting a systematic review can seem arduous or time consuming, but with the use of appropriate tools and resources, and with thorough planning undertaken before beginning the review, researchers will be able to conduct their systematic reviews efficiently and smoothly.

This article provides an overview of the structure, form and content of systematic reviews, with a particular focus on the literature searching component. It will also discuss tools and resources – including those relating to reporting standards and critical appraisal of the articles included in the review – which will be of use to researchers conducting a systematic review.

Topic selection and planning

In recent years, there has been an explosion in the number of systematic reviews conducted and published ( Chalmers & Fox 2016 , Fontelo & Liu 2018 , Page et al 2015 ) – although a systematic review may be an inappropriate or unnecessary research methodology for answering many research questions. Systematic reviews can be inadvisable for a variety of reasons. It may be that the topic is too new and there are not enough relevant published papers to synthesise and analyse for a systematic review, or, conversely, that many other researchers have already published systematic reviews on the topic. However, if a scoping search appears to yield sufficient relevant studies for evidence synthesis, and indicates that no previous systematic reviews have been published (or that those previously published require an update or have methodological flaws), systematic reviews are likely to be appropriate.

Most systematic reviews take between six and 18 months to complete, and require a minimum of three authors to independently screen search results. Although many university modules require students to complete systematic reviews, due to this time and authorship requirement, it would be better to describe such student reviews as ‘reviews with systematic literature searches,’ as it is not possible to fulfil all the methodological requirements of a systematic review in a piece of work with a single author. Researchers without the available time or number of potential co-authors may prefer to adopt a different approach, such as narrative, scoping, or umbrella reviews. The systematic, transparent searching techniques outlined in this article can be adopted and adapted for use in other forms of literature review ( Grant & Booth 2009 ), for example, while the critical appraisal tools highlighted are appropriate for use in other contexts in which the reliability and applicability of medical research require evaluation.

Once it has been determined that a systematic review is the appropriate methodology for the research, and that there is sufficient time and resources to conduct it, researchers should then spend some time developing their review topic. It is appropriate at this point to do some scoping searches in relevant subject databases, first to ensure that the proposed review is unique, and meets a research need, and second to obtain a broad overview of the literature that exists, and which is likely to be included in the eventual systematic review. Based on this scoping work, the review topic may need to be refined or adapted, possibly to broaden or narrow it in focus. Once reviewers are satisfied with their chosen topic, the next step is to prepare a protocol which states transparently the methodology they intend to follow when conducting their review.

Creating a protocol

A protocol is a description of the proposed systematic review, including methods, the rationale for the review, and steps which will be taken to eliminate bias while conducting the review. Registering the protocol stakes a claim on the research, and it also means that researchers have done a significant portion of the work required before they formally begin the review, as they will have written the Methods section in draft form and planned what will be necessary to document and report by the time the protocol is finished.

Most protocols are registered with PROSPERO (2020), although it is also possible to upload your protocol on an institutional or subject repository, or publish the protocol in a journal. Guidance for creating a protocol can be found at PRISMA-P (The PRISMA Group et al 2015), or by working through the online training on protocols available at the Cochrane Library ( Cochrane Interactive Learning 2019 ).

Reporting standards and structure

PRISMA (the Preferred Reporting Items for Systematic Reviews and Meta-analyses) is 'an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses' ( Moher et al 2009 ). The PRISMA checklist is a useful guideline of content that should be reported and included in the final published version of the systematic review, and will help when in the planning stages as well. Most systematic reviews will be written up using the PRISMA checklist as their underlying structure, so familiarity with this checklist and the content required when reporting the findings of the systematic review should be established at the earliest planning stages of the research.

PRISMA-P (The PRISMA Group et al 2015) is the reporting guidelines for protocols. The EQUATOR Network lists reporting standards for multiple different types of study design ( EQUATOR Network 2020 ). Researchers can search for the right guideline for their type of study. Those undertaking a Cochrane review should select the correct Cochrane Handbook ( Cochrane Training 2020 ) for their review type.

Search strategy

The search strategy for systematic reviews is the main method of collecting the data which will underpin the review's findings. This means that the search must be sufficiently robust – both sensitive and specific – to capture all relevant articles. Ideally, multiple databases and other sources of information should be searched, using a consistent, predetermined search string. Generally, this will involve multiple synonyms for each theme of the review's topic, and a multifield search including freetext terms in (at minimum) the title and abstract, and the controlled vocabulary in the database thesaurus. These words are then combined with the Boolean operators AND, OR and NOT so that search results are both sensitive and specific.

Grey literature

It is likely that systematic reviews will need to include a search of grey literature as well as the peer-reviewed journal articles found through database searching. Grey literature includes unpublished theses, conference proceedings, government reports, unpublished trial data and more. Leaving grey literature out can run the risk of biasing the reviews results ( Goldacre 2011 ).

Searching grey literature can be challenging. Most sources of grey literature cannot be searched with complex Boolean operators and myriad synonymous keywords in the manner of a database. Likewise, the websites and other sources used to search for grey literature are unlikely to have a controlled vocabulary thesaurus. The Canadian Agency for Drugs and Technologies in Health (CADTH) tool is designed to help adapt complex systematic database search strategies for use when searching for grey literature ( CADTH 2009 ).

Snowballing, hand-searching and reference lists

Sometimes it may be appropriate to 'snowball' a search. This involves screening all the articles that cite included papers (the articles which meet the inclusion criteria after screening). Search for the titles of each included article in Web of Science or Scopus (or both), and any listed citing article which meets your inclusion criteria should also be included in the review.

Hand searching involves looking back through the tables of contents of key journals, conference proceedings, or lists of conference presentations relevant to the systematic review topic. Once key journals have been identified, reviewers should plan how many years back they will look – this will need to be done consistently across all journals that are hand-searched.

After reviewers have screened all the papers identified by the database and grey literature searches, and agreed on which will be included in the review, they should check through these articles' reference lists. Any articles in their reference lists which meet all inclusion criteria should also be included in the review.

Librarian co-authorship

There is some evidence that having a librarian co-author on a systematic review can improve the review's quality. A number of recent studies have indicated that librarian involvement improves the reproducibility of the literature searching ( Hameed et al 2020 , Koffel 2015 , Rethlefsen et al 2015 ). Reviews without librarian involvement often have problems with their search strategies – for example Boolean operators used incorrectly, inappropriate search syntax, or a lack of sufficient synonyms for each search term, meaning that relevant studies might be missed ( Golder et al 2008 , Li et al 2014 ). Unfortunately, in some instances, systematic reviews without librarian co-authors will still be published, even if their search strategies have significant methodological flaws ( Brasher & Giustini 2020 ). Librarian involvement will help ensure that the search strategy is robust, and that it is described accurately in the methodology to ensure that the systematic review is reproducible. Generally, if a librarian is developing the search terms, running the searches in databases and writing the search methods, they should be a co-author of the systematic review, whereas if the librarian supports researchers who then conduct the searches themselves, co-authorship is not necessary. This also aligns with the Vancouver recommendations on co-authorship ( International Committee of Medical Journal Editors 2019 ).

After database and grey literature searches are completed, and researchers have identified other papers through hand-searching, they will need to screen the titles and abstracts to determine if they meet the criteria for inclusion. These criteria should be pre-defined (ie: stated in the protocol before searches have begun). Inclusion criteria might relate to the following:

Date range of publication. Study design type. Whether a study focuses on the review's specific disease, condition, or patient population. Whether a study focuses mainly on the review's specific intervention. Whether a study focused on a certain country, region, or healthcare context (for example primary care, outpatient department, critical care unit, or similar).

This list is not exhaustive, and there are many other inclusion criteria to apply, depending on the scope of the topic of the systematic review. It is important that these criteria are stated clearly in the Methods section of both the protocol and systematic review, and that all co-authors understand them.

Generally, articles are screened against these criteria independently by at least two authors. Initially they should screen the titles and abstracts, and then move on to screening the full text for any articles which could not be judged as fulfilling (or not fulfilling) all inclusion criteria on the basis of the information in their titles and abstracts.

Referencing software such as Endnote, EndnoteWeb, Mendeley or Zotero can be used for screening, or reviewers may prefer to use systematic review screening software such as Covidence or Rayyan.

Critical appraisal tools

There are a number of tools and checklists available to help assess the quality of studies to be included in a review. Studies included in a systematic review should be assessed for their quality and reliability. While poor quality studies should not be excluded if they fulfil predefined inclusion criteria, the systematic review should make clear that all included studies have been assessed according to consistent principles of critical appraisal, and the results of that appraisal should be included in the review.

Most critical appraisal tools consist of different checklists to apply to different types of study design. If a systematic review includes multiple types of study design, it is advisable that researchers are consistent about which tools they use – it is preferable to use different checklists from a single source, rather than picking and choosing from a variety of sources.

If the systematic review is only including peer-reviewed, published journal articles, the checklists from either CASP (Critical Appraisal Skills Programme), Centre for Evidence-Based Medicine, SIGN (Scottish Intercollegiate Guidelines Network), or Joanna Briggs Institute will be appropriate ( Brice 2020 , Centre for Evidence-Based Medicine 2020 , Joanna Briggs Institute 2020 , SIGN 2020 ). Reviews which include grey literature should use a grey literature appraisal tool, such as AACODS ( Tyndall 2008 ). There are also risk of bias assessment tools, such as RoBiS for evaluating systematic reviews, and RoB 2 for evaluating randomized controlled trials ( Bristol Medical School 2020 , Sterne et al 2019 ).

One of the main advantages of systematic reviews is that they combine the analysis of the data from a number of primary studies. Most commonly, this is done through meta-analysis – the statistical combination of results from two or more studies. As outlined in the Cochrane Handbook, in interventional studies, a systematic review meta-analysis will seek to answer these three main questions:

What is the direction of effect? What is the size of effect? Is the effect consistent across [all included] studies? ( Higgins et al 2019 )

The researchers will then make a judgement as to the strength of evidence for the effect. If the systematic review is assessing the effectiveness of a variety of different interventions, it may not be possible to combine all studies for meta-analysis as the studies may be sufficiently different to make meta-analysis inappropriate. Researchers should ensure that when interpreting the results they consider the limitations and potential biases of included studies. When reporting the findings it is also usually necessary to consider applicability, and make recommendations – such as for a change in practice.

Systematic reviews – when an appropriate approach to the topic being researched – are a way to synthesize and evaluate the range of evidence available in multiple primary studies. Their methodology is complex, but if the correct reporting guidelines are followed, and researchers make use of tools, resources and the support of librarians and other information specialists, the process will be more straightforward. Planning is key: researchers should have a clear picture of what is involved, and what will need to be documented and reported in any resulting publications, and put measures in place to ensure that they capture all of this essential information.

No competing interests declared .

ORCID iD: Veronica Phillips https://orcid.org/0000-0002-4383-9434

Reference management. Clean and simple.

How to write a systematic literature review [9 steps]

Systematic literature review

What is a systematic literature review?

Where are systematic literature reviews used, what types of systematic literature reviews are there, how to write a systematic literature review, 1. decide on your team, 2. formulate your question, 3. plan your research protocol, 4. search for the literature, 5. screen the literature, 6. assess the quality of the studies, 7. extract the data, 8. analyze the results, 9. interpret and present the results, registering your systematic literature review, frequently asked questions about writing a systematic literature review, related articles.

A systematic literature review is a summary, analysis, and evaluation of all the existing research on a well-formulated and specific question.

Put simply, a systematic review is a study of studies that is popular in medical and healthcare research. In this guide, we will cover:

  • the definition of a systematic literature review
  • the purpose of a systematic literature review
  • the different types of systematic reviews
  • how to write a systematic literature review

➡️ Visit our guide to the best research databases for medicine and health to find resources for your systematic review.

Systematic literature reviews can be utilized in various contexts, but they’re often relied on in clinical or healthcare settings.

Medical professionals read systematic literature reviews to stay up-to-date in their field, and granting agencies sometimes need them to make sure there’s justification for further research in an area. They can even be used as the starting point for developing clinical practice guidelines.

A classic systematic literature review can take different approaches:

  • Effectiveness reviews assess the extent to which a medical intervention or therapy achieves its intended effect. They’re the most common type of systematic literature review.
  • Diagnostic test accuracy reviews produce a summary of diagnostic test performance so that their accuracy can be determined before use by healthcare professionals.
  • Experiential (qualitative) reviews analyze human experiences in a cultural or social context. They can be used to assess the effectiveness of an intervention from a person-centric perspective.
  • Costs/economics evaluation reviews look at the cost implications of an intervention or procedure, to assess the resources needed to implement it.
  • Etiology/risk reviews usually try to determine to what degree a relationship exists between an exposure and a health outcome. This can be used to better inform healthcare planning and resource allocation.
  • Psychometric reviews assess the quality of health measurement tools so that the best instrument can be selected for use.
  • Prevalence/incidence reviews measure both the proportion of a population who have a disease, and how often the disease occurs.
  • Prognostic reviews examine the course of a disease and its potential outcomes.
  • Expert opinion/policy reviews are based around expert narrative or policy. They’re often used to complement, or in the absence of, quantitative data.
  • Methodology systematic reviews can be carried out to analyze any methodological issues in the design, conduct, or review of research studies.

Writing a systematic literature review can feel like an overwhelming undertaking. After all, they can often take 6 to 18 months to complete. Below we’ve prepared a step-by-step guide on how to write a systematic literature review.

  • Decide on your team.
  • Formulate your question.
  • Plan your research protocol.
  • Search for the literature.
  • Screen the literature.
  • Assess the quality of the studies.
  • Extract the data.
  • Analyze the results.
  • Interpret and present the results.

When carrying out a systematic literature review, you should employ multiple reviewers in order to minimize bias and strengthen analysis. A minimum of two is a good rule of thumb, with a third to serve as a tiebreaker if needed.

You may also need to team up with a librarian to help with the search, literature screeners, a statistician to analyze the data, and the relevant subject experts.

Define your answerable question. Then ask yourself, “has someone written a systematic literature review on my question already?” If so, yours may not be needed. A librarian can help you answer this.

You should formulate a “well-built clinical question.” This is the process of generating a good search question. To do this, run through PICO:

  • Patient or Population or Problem/Disease : who or what is the question about? Are there factors about them (e.g. age, race) that could be relevant to the question you’re trying to answer?
  • Intervention : which main intervention or treatment are you considering for assessment?
  • Comparison(s) or Control : is there an alternative intervention or treatment you’re considering? Your systematic literature review doesn’t have to contain a comparison, but you’ll want to stipulate at this stage, either way.
  • Outcome(s) : what are you trying to measure or achieve? What’s the wider goal for the work you’ll be doing?

Now you need a detailed strategy for how you’re going to search for and evaluate the studies relating to your question.

The protocol for your systematic literature review should include:

  • the objectives of your project
  • the specific methods and processes that you’ll use
  • the eligibility criteria of the individual studies
  • how you plan to extract data from individual studies
  • which analyses you’re going to carry out

For a full guide on how to systematically develop your protocol, take a look at the PRISMA checklist . PRISMA has been designed primarily to improve the reporting of systematic literature reviews and meta-analyses.

When writing a systematic literature review, your goal is to find all of the relevant studies relating to your question, so you need to search thoroughly .

This is where your librarian will come in handy again. They should be able to help you formulate a detailed search strategy, and point you to all of the best databases for your topic.

➡️ Read more on on how to efficiently search research databases .

The places to consider in your search are electronic scientific databases (the most popular are PubMed , MEDLINE , and Embase ), controlled clinical trial registers, non-English literature, raw data from published trials, references listed in primary sources, and unpublished sources known to experts in the field.

➡️ Take a look at our list of the top academic research databases .

Tip: Don’t miss out on “gray literature.” You’ll improve the reliability of your findings by including it.

Don’t miss out on “gray literature” sources: those sources outside of the usual academic publishing environment. They include:

  • non-peer-reviewed journals
  • pharmaceutical industry files
  • conference proceedings
  • pharmaceutical company websites
  • internal reports

Gray literature sources are more likely to contain negative conclusions, so you’ll improve the reliability of your findings by including it. You should document details such as:

  • The databases you search and which years they cover
  • The dates you first run the searches, and when they’re updated
  • Which strategies you use, including search terms
  • The numbers of results obtained

➡️ Read more about gray literature .

This should be performed by your two reviewers, using the criteria documented in your research protocol. The screening is done in two phases:

  • Pre-screening of all titles and abstracts, and selecting those appropriate
  • Screening of the full-text articles of the selected studies

Make sure reviewers keep a log of which studies they exclude, with reasons why.

➡️ Visit our guide on what is an abstract?

Your reviewers should evaluate the methodological quality of your chosen full-text articles. Make an assessment checklist that closely aligns with your research protocol, including a consistent scoring system, calculations of the quality of each study, and sensitivity analysis.

The kinds of questions you'll come up with are:

  • Were the participants really randomly allocated to their groups?
  • Were the groups similar in terms of prognostic factors?
  • Could the conclusions of the study have been influenced by bias?

Every step of the data extraction must be documented for transparency and replicability. Create a data extraction form and set your reviewers to work extracting data from the qualified studies.

Here’s a free detailed template for recording data extraction, from Dalhousie University. It should be adapted to your specific question.

Establish a standard measure of outcome which can be applied to each study on the basis of its effect size.

Measures of outcome for studies with:

  • Binary outcomes (e.g. cured/not cured) are odds ratio and risk ratio
  • Continuous outcomes (e.g. blood pressure) are means, difference in means, and standardized difference in means
  • Survival or time-to-event data are hazard ratios

Design a table and populate it with your data results. Draw this out into a forest plot , which provides a simple visual representation of variation between the studies.

Then analyze the data for issues. These can include heterogeneity, which is when studies’ lines within the forest plot don’t overlap with any other studies. Again, record any excluded studies here for reference.

Consider different factors when interpreting your results. These include limitations, strength of evidence, biases, applicability, economic effects, and implications for future practice or research.

Apply appropriate grading of your evidence and consider the strength of your recommendations.

It’s best to formulate a detailed plan for how you’ll present your systematic review results. Take a look at these guidelines for interpreting results from the Cochrane Institute.

Before writing your systematic literature review, you can register it with OSF for additional guidance along the way. You could also register your completed work with PROSPERO .

Systematic literature reviews are often found in clinical or healthcare settings. Medical professionals read systematic literature reviews to stay up-to-date in their field and granting agencies sometimes need them to make sure there’s justification for further research in an area.

The first stage in carrying out a systematic literature review is to put together your team. You should employ multiple reviewers in order to minimize bias and strengthen analysis. A minimum of two is a good rule of thumb, with a third to serve as a tiebreaker if needed.

Your systematic review should include the following details:

A literature review simply provides a summary of the literature available on a topic. A systematic review, on the other hand, is more than just a summary. It also includes an analysis and evaluation of existing research. Put simply, it's a study of studies.

The final stage of conducting a systematic literature review is interpreting and presenting the results. It’s best to formulate a detailed plan for how you’ll present your systematic review results, guidelines can be found for example from the Cochrane institute .

systematic literature review format

Charles Sturt University

Literature Review: Systematic literature reviews

  • Traditional or narrative literature reviews
  • Scoping Reviews
  • Systematic literature reviews
  • Annotated bibliography
  • Keeping up to date with literature
  • Finding a thesis
  • Evaluating sources and critical appraisal of literature
  • Managing and analysing your literature
  • Further reading and resources

Systematic reviews

Systematic and systematic-like reviews

Charles Sturt University library has produced a comprehensive guide for Systematic and systematic-like literature reviews. A comprehensive systematic literature review can often take a team of people up to a year to complete. This guide provides an overview of the steps required for systematic reviews:

  • Identify your research question
  • Develop your protocol
  • Conduct systematic searches (including the search strategy, text mining, choosing databases, documenting and reviewing
  • Critical appraisal
  • Data extraction and synthesis
  • Writing and publishing .
  • Systematic and systematic-like reviews Library Resource Guide

Systematic literature review

A systematic literature review (SLR) identifies, selects and critically appraises research in order to answer a clearly formulated question (Dewey, A. & Drahota, A. 2016). The systematic review should follow a clearly defined protocol or plan where the criteria is clearly stated before the review is conducted. It is a comprehensive, transparent search conducted over multiple databases and grey literature that can be replicated and reproduced by other researchers. It involves planning a well thought out search strategy which has a specific focus or answers a defined question. The review identifies the type of information searched, critiqued and reported within known timeframes. The search terms, search strategies (including database names, platforms, dates of search) and limits all need to be included in the review.

Pittway (2008) outlines seven key principles behind systematic literature reviews

  • Transparency
  • Integration
  • Accessibility

Systematic literature reviews originated in medicine and are linked to evidence based practice. According to Grant & Booth (p 91, 2009) "the expansion in evidence-based practice has lead to an increasing variety of review types". They compare and contrast 14 review types, listing the strengths and weaknesses of each review. 

Tranfield et al (2003) discusses the origins of the evidence-based approach to undertaking a literature review and its application to other disciplines including management and science.

References and additional resources

Dewey, A. & Drahota, A. (2016) Introduction to systematic reviews: online learning module Cochrane Training   https://training.cochrane.org/interactivelearning/module-1-introduction-conducting-systematic-reviews

Gough, David A., David Gough, Sandy Oliver, and James Thomas. An Introduction to Systematic Reviews. Systematic Reviews. London: SAGE, 2012.

Grant, M. J. & Booth, A. (2009) A typology of reviews: An analysis of 14 review types and associated methodologies. Health Information & Libraries Journal 26(2), 91-108

Munn, Z., Peters, M. D. J., 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 Med Res Methodol, 18(1), 143. https://doi.org/10.1186/s12874-018-0611-x 

Pittway, L. (2008) Systematic literature reviews. In Thorpe, R. & Holt, R. The SAGE dictionary of qualitative management research. SAGE Publications Ltd doi:10.4135/9780857020109

Tranfield, D., Denyer, D & Smart, P. (2003) Towards a methodology for developing evidence-informed management knowledge by means of systematic review . British Journal of Management 14 (3), 207-222

Evidence based practice - an introduction : Literature reviews/systematic reviews

Evidence based practice - an introduction is a library guide produced at CSU Library for undergraduates. The information contained in the guide is also relevant for post graduate study and will help you to understand the types of research and levels of evidence required to conduct evidence based research.

  • Evidence based practice an introduction
  • << Previous: Scoping Reviews
  • Next: Annotated bibliography >>
  • Last Updated: Jan 16, 2024 1:39 PM
  • URL: https://libguides.csu.edu.au/review

Acknowledgement of Country

Charles Sturt University is an Australian University, TEQSA Provider Identification: PRV12018. CRICOS Provider: 00005F.

How to Write a Systematic Review of the Literature

Affiliations.

  • 1 1 Texas Tech University, Lubbock, TX, USA.
  • 2 2 University of Florida, Gainesville, FL, USA.
  • PMID: 29283007
  • DOI: 10.1177/1937586717747384

This article provides a step-by-step approach to conducting and reporting systematic literature reviews (SLRs) in the domain of healthcare design and discusses some of the key quality issues associated with SLRs. SLR, as the name implies, is a systematic way of collecting, critically evaluating, integrating, and presenting findings from across multiple research studies on a research question or topic of interest. SLR provides a way to assess the quality level and magnitude of existing evidence on a question or topic of interest. It offers a broader and more accurate level of understanding than a traditional literature review. A systematic review adheres to standardized methodologies/guidelines in systematic searching, filtering, reviewing, critiquing, interpreting, synthesizing, and reporting of findings from multiple publications on a topic/domain of interest. The Cochrane Collaboration is the most well-known and widely respected global organization producing SLRs within the healthcare field and a standard to follow for any researcher seeking to write a transparent and methodologically sound SLR. Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA), like the Cochrane Collaboration, was created by an international network of health-based collaborators and provides the framework for SLR to ensure methodological rigor and quality. The PRISMA statement is an evidence-based guide consisting of a checklist and flowchart intended to be used as tools for authors seeking to write SLR and meta-analyses.

Keywords: evidence based design; healthcare design; systematic literature review.

  • Evidence-Based Medicine* / organization & administration
  • Research Design*
  • Systematic Reviews as Topic*

Systematic Reviews and Meta Analysis

  • Getting Started
  • Guides and Standards
  • Review Protocols
  • Databases and Sources
  • Randomized Controlled Trials
  • Controlled Clinical Trials
  • Observational Designs
  • Tests of Diagnostic Accuracy
  • Software and Tools
  • Where do I get all those articles?
  • Collaborations
  • EPI 233/528
  • Countway Mediated Search
  • Risk of Bias (RoB)

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 .

  • Next: Guides and Standards >>
  • Last Updated: Feb 14, 2024 2:47 PM
  • URL: https://guides.library.harvard.edu/meta-analysis

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  • Macquarie University Library
  • Subject and Research Guides

Systematic Reviews

  • Step 10: Templates, Write & Publish
  • Step 1: Check Protocols & Guides
  • Step 2: Form a Question
  • Step 3: Develop a Search Strategy & Criteria
  • Grey Literature
  • Documenting the Search
  • Step 5: Export Results with EndNote, Mendeley
  • Review Software and Tools
  • Step 6: PRISMA Flow Diagram & Screen
  • Step 7: Extract Data
  • Step 8: Appraise Studies & Assess Risk of Bias
  • Step 9: Synthesise & Interpret, Meta-analyses
  • Non-Health Systematic Reviews

Writing Your Review

When writing up your systematic review keep in mind the specific guidelines for structuring your review. Systematic review standards are elements that should be reported in any published systematic review. Also there may be other 'Instructions to Authors' provided by the journals or organisations in which you plan to publish.

The PRISMA statement can be followed to ensure reliable coverage of the systematic review methods, results and conclusions. The PRISMA Elaboration and Explanation (E&E) document that accompanies the PRISMA statement provides instructions for each of the items on the checklist.

  • PRISMA Statement
  • PRISMA Elaboration and Explanation Document
  • Moher D, Shamseer L, Clarke M, Ghersi D, Liberati A, Petticrew M, et al. Preferred reporting items for systematic review and meta-analysis protocols (PRISMA-P) 2015 statement

Strategic Publishing

  • RV2 Checklist To help make informed decisions before publishing, MQ has developed the RV2 checklist to assist with selecting appropriate peer-reviewed journals.
  • Strategic Publishing Guide Strategic publishing guide by DVC-R and the Library
  • Think Check Submit Think. Check. Submit. helps researchers identify trusted journals for their research. Through a range of tools and practical resources, this international, cross-sector initiative aims to educate researchers, promote integrity, and build trust in credible research and publications.

Templates for SRs

This link is to best practice examples from Cochrane on how to write about your searches in a Cochrane review.

You can adapt examples to suit your systematic review.

  • Search Text Templates for Reviews and Updates

Further reading

  • Article: Choosing the right journal for your systematic review
  • << Previous: Step 9: Synthesise & Interpret, Meta-analyses
  • Next: Non-Health Systematic Reviews >>
  • Last Updated: Dec 5, 2023 2:23 PM
  • URL: https://libguides.mq.edu.au/systematic_reviews

JEPS Bulletin

The Official Blog of the Journal of European Psychology Students

Writing a Systematic Literature Review

Investigating concepts associated with psychology requires an indefinite amount of reading. Hence, good literature reviews are an inevitably needed part of providing the modern scientists with a broad spectrum of knowledge. In order to help, this blog post will introduce you to the basics of literature reviews and explain a specific methodological approach towards writing one, known as the systematic literature review.

Literature review is a term associated with the process of collecting, checking and (re)analysing data from the existing literature with a particular search question in mind. The latter could be for example:

  • What are the effects of yoga associated with individual’s subjective well-being?
  • Does brief psychotherapy produce beneficial outcomes for individuals diagnosed with agoraphobia?
  • What personality traits are most commonly associated with homelessness in the modern literature?

A literature review (a) defines a specific issue, concept, theory, phenomena; (b) compiles published literature on a topic; (c) summarises critical points of current knowledge about the problem and (d) suggests next steps in addressing it.

Literature reviews can be based on all sorts of information found in scientific journals, books, academic dissertations, electronic bibliographic databases and the rest of the Internet.  Electronic databases such as PsycINFO , PubMed , Web of Science could be a good starting point. Some of them, like EBSCOhost , ScienceDirect , SciELO , and ProQuest , provide full-text information, while others provide the users mostly with the abstracts of the material. Besides scientific literature, literature reviews often include the so called gray literature . This refers to the material that is either unpublished or published in non-commercial form (e.g., theses, dissertations, government reports, fact sheets, pre-prints of articles). Excluding it completely from a literature review is inappropriate because the search should be always as complete as possible in order to reduce the risk of publication bias. However, when reviewing the material on for example Google Scholar , Science.gov , Social Science Research Network , or PsycEXTRA it should be kept in mind that such search engines also display the material without peer-review and have therefore less credibility regarding the information they are disclosing.

When performing literature reviews, the use of appropriately selected terminology is essential, since it allows the researchers much clearer communication. In psychology, without some commonly agreed lists of terms, we would all get lost in the variety of concepts and vocabularies that could be applied. A typical recommendation for where to look for such index terms would be ‘ Thesaurus of Psychological Index Terms (2007) ’, which includes nearly 9,000 most commonly cross-referenced terms in psychology. In addition, electronic databases mentioned before sometimes prompt the use of the so-called Boolean operators , simple words such as AND, OR, NOT, or AND NOT. These are used for combining and/or excluding specific terms in your search and sometimes allow to obtain more focused and productive results in the search. Other tools to make search strategy more comprehensive and focused are also truncations – a tool for searching terminologies that have same initial roots (e.g., anxiety and anxious) and wildcards for words with spelling deviations (e.g., man and men). It is worth noting that the databases slightly differ in how they label the index terms and utilize specific search tools in their systems.

Among authors, there is not much coherence about different types of literature reviews but in general, most recognize at least two: traditional and systematic. The main difference between them is situated in the process of collecting and selecting data and the material for the review. Systematic literature review, as the name implies, is the more structured of the two and is thought to be more credible. On the other hand, traditional is thought to heavily depend on the researcher’s decisions regarding the data selection and, consequently, evaluation and results. Systematic protocol of the systematic literature review can be therefore understood as an optional solution for controlling the incomplete and possibly biased reports of traditional reviews.

THE SYSTEMATIC LITERATURE REVIEW

The systematic literature review is a method/process/protocol in which a body of literature is aggregated, reviewed and assessed while utilizing pre-specified and standardized techniques. In other words, to reduce bias, the rationale, the hypothesis, and the methods of data collection are prepared before the review and are used as a guide for performing the process. Just like it is for the traditional literature reviews, the goal is to identify, critically appraise, and summarize the existing evidence concerning a clearly defined problem.

Systematic literature reviews allow us to examine conflicting and/or coincident findings, as well as to identify themes that require further investigation. Furthermore, they include the possibility of evaluating consistency and generalization of the evidence regarding specific scientific questions and are, therefore, also of great practical value within the psychological field. The method is particularly useful to integrate the information of a group of studies investigating the same phenomena and it typically focuses on a very specific empirical question, such as ‘Does the Rational Emotive Therapy intervention benefit the well-being of the patients diagnosed with depression?’.

Systematic literature reviews include all (or most) of the following characteristics:

  • Objectives clearly defined a priori;
  • Explicit pre-defined criteria for inclusion/exclusion of the literature;
  • Predetermined search strategy in the collection of the information and systematic following of the process;
  • Predefined characteristic criteria applied to all the sources utilized and clearly presented in the review;
  • Systematic evaluation of the quality of the studies included in the review;
  • Identification of the excluded sources of literature and justification for excluding them;
  • Analysis/synthesis of the information (i.e., comparison of the results, qualitative synthesis of the results, meta-analysis);
  • References to the incoherences and the errors found in the selected material.

The process of performing a systematic literature review consists of several stages and can be reported in a form of an original research article with the same name (i.e., systematic literature review):

systematic literature review format

1: Start by clearly defining the objective of the review or form a structured research question.

Place in the research article: Title, Abstract, Introduction.

Example of the objective: The objective of this literature revision is to systematically review and analyse the current research on the effects of music on the anxiety levels of children in hospital settings.

Example of a structured research question: What are the most important factors associated with the development of PTSD in soldiers?

Tip: In the title, identify that the report is a systematic literature review.

2: Clearly specify the methodology of the review and define eligibility criteria (i.e., study selection criteria that the published material must meet in order to be included or excluded from the study). The search should be extensive.

Place in the research article: Methods.

Examples of inclusion criteria: Publication was an academic and peer-reviewed study. Publication was a study that examined the effects of regular physical exercise intervention on depression and included a control group.

Examples of exclusion criteria: Publication was involving male adults. Studies that also examined non-physical activities as interventions. Studies that were only published in a language other than English.

Tips: The eligibility criteria sometimes fit to be presented in tables.

3: Retrieve eligible literature and thoroughly report your search strategy throughout the process. (Ideally, the selection process is performed by at least two independent investigators.)

Example: The EBSCOhost and PsychInfo electronic databases from 2010 to 2017 were searched. These were chosen because of the psychological focus that encompasses psychosocial effects of emotional abuse in childhood. Search terms were ‘emotional abuse’, ‘childhood’, ‘psychosocial effects’, and ‘psychosocial consequences’.  The EBSCOhost produced 200 results from the search criteria, while PsychInfo produced 467, for a total of 667 articles. […] Articles were rejected if it was determined from the title and the abstract that the study failed to meet the inclusion criteria. Any ambiguities regarding the application of the selection criteria were resolved through discussions between all the researchers involved.

Tip: Sometimes it is nice to represent the selection process in a graphical representation; in the form of a decision tree or a flow diagram (check PRISMA ).

4: Assess the methodological quality of the selected literature whenever possible and exclude the articles with low methodological quality. Keep in mind that the quality of the systematic review depends on the validity and the quality of the studies included in the review.

Examples of the instruments available for evaluating the quality of the studies: PEDro, Jadad scale, the lists of Delphi, OTseeker, Maastricht criteria.

Tip: Present the excluded articles as a part of the selection process mentioned in step 3.

5: Proceed with the so-called characterization of the studies. Decide which data to look for in all the selected studies and present it in a summarized way. If the information is missing in some specific paper, always register it in your reports. (Ideally, the characterization of the studies is performed by at least two independent investigators.)

Place in the research article: Results.

Examples of the information that should and/or could be collected for characterization of the literature: authors, year, sample size, study design, aims and objectives, findings/results, limitations.

Tip: Sometimes results can be presented nicely in a form of a table depicting the main characteristics.

6: Write a synthesis of the results – integrate the results of different studies and  interpret them in a narrative form.

Place in the research article: Interpretation, Conclusions.

Patterns discovered as results should be summarized in a qualitative, narrative form. Modulate one (or more) general arguments for organizing the review. Some trick to help you do this is to choose two or three main information sources (e.g., articles, books, other literature reviews) to explain the results of other studies through a similar way of organization. Connect the information reported by different sources and do not just summarize the results. Find patterns in the results of different studies, identify them, address the theoretical and/or methodological conflicts and try to interpret them. Summarize the principal conclusions and evaluate the current state on the subject by pointing out possible further directions.

CONCLUSIONS

The results emerging from the data that were included in such retrospective studies can lead to a certain level of credibility regarding their conclusions. Actually, systematic literature reviews are thought to be one of our best methods to summarize and synthesize evidence about some specific research question and are often used as the main ‘practice making guidelines’ in many health care disciplines. Therefore, it is no wonder why systematic reviews are gaining popularity among researchers and why journals are moving in this direction as well. This also shows in the development of more and more specific guidelines and checklists for writing systematic literature reviews (see for example PRISMA or Cochrane Handbook for Systematic Reviews of Interventions ). To find examples of systematic literature review articles you can check Cochrane Database of Systematic Reviews , BioMed Central’s Systematic Reviews Journal , and PROSPERO . If you are aware of the concept of ‘registered reports’, it is worth mentioning that submitting with PROSPERO provides you with the option of publishing the latter as well. I suggest that you go through the list of useful resources provided below and hopefully, you can get enough information about anything related that remained unanswered. Now, I encourage you to try to be a little more to be systematic whenever researching some topic, to try to write a systematic literature review yourself and to maybe even consider submitting it to JEPS .

USEFUL RESOURCES

  • Cochrane Database of Systematic Reviews : http://www.cochranelibrary.com/cochrane-database-of-systematic-reviews/

EBSCOhost : https://search.ebscohost.com/

Google Scholar : https://scholar.google.com/

PRISMA : http://www.prisma-statement.org/

PROSPERO : https://www.crd.york.ac.uk/prospero/

ProQuest : http://www.proquest.com/

PsycEXTRA : http://www.apa.org/pubs/databases/psycextra/index.aspx :

PsycINFO : http://www.apa.org/pubs/databases/psycinfo/index.aspx

PubMed : https://www.ncbi.nlm.nih.gov/pubmed/

SciELO : http://www.scielo.org/php/index.php?lang=en

Science.gov : https://www.science.gov/

ScienceDirect : http://www.sciencedirect.com/

Scorpus : http://www.scopus.com/freelookup/form/author.uri

Social Science Research Network : https://www.ssrn.com/en/

Systematic Reviews Journal (BIOMED) : https://systematicreviewsjournal.biomedcentral.com/

Web of Science : https://webofknowledge.com/

Other sources

  • Sampaio, R. F., & Mancini, M. C. (2007). Systematic review studies: A guide for a careful synthesis of scientific evidence. Brasilian Journal of Physical Therapy, 11 (1), 77-82. doi:http://dx.doi.org/10.1590/S1413-35552
  • Tuleya, L. G. (2007). Thesaurus of psychological index terms . Washington, DC: American Psychological Association.

Eva Štrukelj

Eva Štrukelj

Eva Štrukelj is currently studying Clinical and Health Psychology at the University of Algarve in Portugal. Her main areas of interest are social psychology and health psychology. Regarding research, she is particularly curious about stigma and with it related topics.

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  • How to write a good literature review article?
  • How to search for literature?
  • Editorial perspective on scientific writing: An interview with Dr. Renata Franc
  • Peer Review Process – Tips for Early Career Scientists

Dahlgren Memorial Library

The Graduate Health & Life Sciences Research Library at Georgetown University Medical Center

Systematic reviews.

  • Should I do a systematic review?
  • Writing the Protocol
  • Building a Systematic Search
  • Where to Search
  • Managing Project Data
  • How can a DML librarian help?

How do I write a protocol?

The protocol serves as a roadmap for your review and specifies the objectives, methods, and outcomes of primary interest of the systematic review. Having a protocol promotes transparency and can be helpful for project management. Some journals require you to submit your protocol along with your manuscript. 

A good way to familiarize yourself with research protocols is to take a look at those registered on PROSPERO. PROSPERO's registration form includes 22 mandatory fields and 18 optional fields which will help you to explain every aspect of your research plan. 

  • PROSPERO - International prospective register of systematic reviews

A protocol ideally includes the following:

  • Databases to be searched and additional sources (particularly for grey literature)
  • Keywords to be used in the search strategy
  • Limits applied to the search
  • Screening process
  • Data to be extracted
  • Summary of data to be reported

Once you have written your protocol, it is advisable to register it. Registering your protocol is a good way to announce that you are working on a review, so that others do not start working on it.

The University of Warwick's protocol template is available below and is a great tool for planning your protocol. 

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Duke University Libraries

Literature Reviews

  • Getting started

What is a literature review?

Why conduct a literature review, stages of a literature review, lit reviews: an overview (video), check out these books.

  • Types of reviews
  • 1. Define your research question
  • 2. Plan your search
  • 3. Search the literature
  • 4. Organize your results
  • 5. Synthesize your findings
  • 6. Write the review
  • Thompson Writing Studio This link opens in a new window
  • Need to write a systematic review? This link opens in a new window

systematic literature review format

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systematic literature review format

Definition: A literature review is a systematic examination and synthesis of existing scholarly research on a specific topic or subject.

Purpose: It serves to provide a comprehensive overview of the current state of knowledge within a particular field.

Analysis: Involves critically evaluating and summarizing key findings, methodologies, and debates found in academic literature.

Identifying Gaps: Aims to pinpoint areas where there is a lack of research or unresolved questions, highlighting opportunities for further investigation.

Contextualization: Enables researchers to understand how their work fits into the broader academic conversation and contributes to the existing body of knowledge.

systematic literature review format

tl;dr  A literature review critically examines and synthesizes existing scholarly research and publications on a specific topic to provide a comprehensive understanding of the current state of knowledge in the field.

What is a literature review NOT?

❌ An annotated bibliography

❌ Original research

❌ A summary

❌ Something to be conducted at the end of your research

❌ An opinion piece

❌ A chronological compilation of studies

The reason for conducting a literature review is to:

systematic literature review format

Literature Reviews: An Overview for Graduate Students

While this 9-minute video from NCSU is geared toward graduate students, it is useful for anyone conducting a literature review.

systematic literature review format

Writing the literature review: A practical guide

Available 3rd floor of Perkins

systematic literature review format

Writing literature reviews: A guide for students of the social and behavioral sciences

Available online!

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So, you have to write a literature review: A guided workbook for engineers

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Telling a research story: Writing a literature review

systematic literature review format

The literature review: Six steps to success

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Systematic approaches to a successful literature review

Request from Duke Medical Center Library

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Doing a systematic review: A student's guide

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  • Last Updated: Feb 15, 2024 1:45 PM
  • URL: https://guides.library.duke.edu/lit-reviews

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Midwestern University Homepage

Faculty Research Resources: Systematic Review & Evidence Synthesis

  • Research Tools
  • Systematic Review & Evidence Synthesis

Types of Reviews

Evidence synthesis is any type of research methodology where researchers identify, select, and combine results from multiple studies.

This area of research is used to identify gaps in the evidence and establish a base for evidence-based decision-making.

Few common types of evidence synthesis are:

  • Systematic review
  • Literature (narrative) review
  • Scoping review
  • Rapid review
  • Meta-analysis
  • Literature Reviews Explained (LITR-EX)
  • Types of Evidence Synthesis - Evidence Synthesis Methods Interest Group

What is a Systematic Review?

Systematic reviews collect identify, appraise, and synthesize all available evidence to answer a well-formulated research question using explicit, reproducible methodology.

Key characteristics include: 

  • a systematic search in relevant subject databases
  • results independently screened according to pre-defined inclusion and exclusion criteria
  • critical appraisal of selected research studies
  • thorough presentation of the characteristics and findings of the included studies

Librarian Assistance

Librarians offer various levels of assistance with evidence synthesis. Refer to the library's policy for more information:

  • Policy for Librarian Searches for SRs and Other Complex Searches

Organizations with Evidence Synthesis Information

Cochrane, Scottish Intercollegiate Guidelines Network (SIGN), and Joanna Briggs Institute (JBI) are organizations that support evidence-based health decisions with evidence synthesis resources.

  • Cochrane Handbook
  • JBI Manual for Evidence Synthesis
  • JBI Scoping Review Network

Register a Protocol

It is best practice to register a systematic review with PROSPERO or another registry like Open Science Framework (OSF). 

  • Open Science Framework (OSF)

Protocol Templates & Guidance

  • PROSPERO Guidance
  • PRISMA-P - Protocols
  • Scoping Review Protocol: Guidance & Template - OSF
  • JBI Scoping Review Protocol Template

Systematic Review Databases & Searching

Systematic review searches are distinctive in their comprehensiveness.  Studies show that consulting with a librarian improve the quality of systematic review searches.

Librarians can advise on the most appropriate search strategies and databases.

Common systematic review databases include:

  • Cochrane Central Register of Controlled Trials

systematic literature review format

Grey Literature

Grey literature includes conference papers, dissertations, theses, trial registers, and is not controlled by commercial publishing. 

A few repositories of grey literature are:

  • ClinicalTrials.gov

Conducting a Systematic Review: An Overview of the Process from NNLM

Running Time (56:37)

Reporting Guidelines

P referred R eporting I tems for S ystematic R eviews and M eta- A nalyses (PRISMA) 

  • PRISMA: Statement, E&E, Checklist
  • PRISMA-NMA - Network Meta-Analyses

Covidence is a web-based software for screening and data extraction provided by Midwestern University Libraries. 

  • Covidence Registration *You must register for Covidence with a midwestern.edu email address*

Rayyan is an alternative to Covidence. It is a free online tool aiding in the screening and coding of studies for systematic reviews.

EndNote 21 is a reference management software that facilitates documenting record retrieval. 

  • Using EndNote 21 (Desktop) from Midwestern University
  • Using EndNote for Systematic Reviews from UCL

Critical Appraisal Tools

Evaluate studies for quality using assessment tools such as the Modified Downs & Black Checklist . Other examples of critical appraisal tools include: 

  • CATevaluation
  • Critical Appraisal Skills Checklists - CASP
  • Critical Appraisal Tools - JBI
  • Critical Appraisal Worksheets - CEBM
  • Risk of Bias 2 (RoB 2) tool
  • ROBINS-I tool
  • SIGN Checklists

Reading List

  • Boland A, Cherry MG, Dickson R. Doing a systematic review: a student's guide . 2nd ed. SAGE; 2017.
  • Foster M J, Jewell S T. Assembling the pieces of a systematic review: guide for librarians . Rowman & Littlefield; 2017.
  • Grant MJ, Booth A. A typology of reviews: an analysis of 14 review types and associated methodologies. Health Info Libr J . 2009;26(2):91-108. doi:10.1111/j.1471-1842.2009.00848.x
  • Haile ZT. Critical Appraisal Tools and Reporting Guidelines. J Hum Lact . 2022;38(1):21-27. doi:10.1177/08903344211058374
  • Mak S, Thomas A. An Introduction to Scoping Reviews.  J Grad Med Educ . 2022;14(5):561-564. doi:10.4300/JGME-D-22-00620.1
  • PLoS Medicine Editors. Best practice in systematic reviews: the importance of protocols and registration. PLoS Med . 2011;8(2):e1001009. doi:10.1371/journal.pmed.1001009
  • Stellrecht E, Samuel A, Maggio LA. A reader’s guide to medical education systematic reviews. J Grad Méd Educ . 2022;14(2):176-177. doi:10.4300/jgme-d-22-00114.1
  • Conducting a Systematic Review: An Overview of the Process - NNLM (56:37)
  • Covidence Webinars
  • JBI Systematic Reviews Playlist
  • The Pieces of Systematic Review Series with Margaret Foster - NNLM SCR
  • Rayyan How-To Videos
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What’s Included: Literature Review Template

This template is structure is based on the tried and trusted best-practice format for formal academic research projects such as dissertations and theses. The literature review template includes the following sections:

  • Before you start – essential groundwork to ensure you’re ready
  • The introduction section
  • The core/body section
  • The conclusion /summary
  • Extra free resources

Each section is explained in plain, straightforward language , followed by an overview of the key elements that you need to cover. We’ve also included practical examples and links to more free videos and guides to help you understand exactly what’s required in each section.

The cleanly-formatted Google Doc can be downloaded as a fully editable MS Word Document (DOCX format), so you can use it as-is or convert it to LaTeX.

PS – if you’d like a high-level template for the entire thesis, you can we’ve got that too .

FAQs: Literature Review Template

What format is the template (doc, pdf, ppt, etc.).

The literature review chapter template is provided as a Google Doc. You can download it in MS Word format or make a copy to your Google Drive. You’re also welcome to convert it to whatever format works best for you, such as LaTeX or PDF.

What types of literature reviews can this template be used for?

The template follows the standard format for academic literature reviews, which means it will be suitable for the vast majority of academic research projects (especially those within the sciences), whether they are qualitative or quantitative in terms of design.

Keep in mind that the exact requirements for the literature review chapter will vary between universities and degree programs. These are typically minor, but it’s always a good idea to double-check your university’s requirements before you finalize your structure.

Is this template for an undergrad, Master or PhD-level thesis?

This template can be used for a literature review at any level of study. Doctoral-level projects typically require the literature review to be more extensive/comprehensive, but the structure will typically remain the same.

Can I modify the template to suit my topic/area?

Absolutely. While the template provides a general structure, you should adapt it to fit the specific requirements and focus of your literature review.

What structural style does this literature review template use?

The template assumes a thematic structure (as opposed to a chronological or methodological structure), as this is the most common approach. However, this is only one dimension of the template, so it will still be useful if you are adopting a different structure.

Does this template include the Excel literature catalog?

No, that is a separate template, which you can download for free here . This template is for the write-up of the actual literature review chapter, whereas the catalog is for use during the literature sourcing and sorting phase.

How long should the literature review chapter be?

This depends on your university’s specific requirements, so it’s best to check with them. As a general ballpark, literature reviews for Masters-level projects are usually 2,000 – 3,000 words in length, while Doctoral-level projects can reach multiples of this.

Can I include literature that contradicts my hypothesis?

Yes, it’s important to acknowledge and discuss literature that presents different viewpoints or contradicts your hypothesis. So, don’t shy away from existing research that takes an opposing view to yours.

How do I avoid plagiarism in my literature review?

Always cite your sources correctly and paraphrase ideas in your own words while maintaining the original meaning. You can always check our plagiarism score before submitting your work to help ease your mind. 

Do you have an example of a populated template?

We provide a walkthrough of the template and review an example of a high-quality literature research chapter here .

Can I share this literature review template with my friends/colleagues?

Yes, you’re welcome to share this template in its original format (no editing allowed). If you want to post about it on your blog or social media, all we ask is that you reference this page as your source.

Do you have templates for the other dissertation/thesis chapters?

Yes, we do. You can find our full collection of templates here .

Can Grad Coach help me with my literature review?

Yes, you’re welcome to get in touch with us to discuss our private coaching services , where we can help you work through the literature review chapter (and any other chapters).

Free Webinar: Literature Review 101

  • Open access
  • Published: 24 February 2024

Does transanal drainage tubes placement have an impact on the incidence of anastomotic leakage after rectal cancer surgery? a systematic review and meta-analysis

  • Yating Liu 1   na1 ,
  • Xuhua Hu 2   na1 ,
  • Yu Huang 1 ,
  • Pengfei Zhang 1 ,
  • Yaoguang Hao 1 ,
  • Hongyan Li 1 &
  • Guiying Wang 3  

BMC Cancer volume  24 , Article number:  263 ( 2024 ) Cite this article

Metrics details

Whether Transanal drainage tubes (TDTs) placement reduces the occurrence of anastomotic leakage (AL) after rectal cancer (RC) surgery remains controversial. Most existing meta-analyses rely on retrospective studies, while the prospective studies present an inadequate level of evidence.

A systematic review and meta-analysis of prospective studies on TDTs placement in RC patients after surgery was conducted. The main analysis index was the incidence of AL, Grade B AL, and Grade C AL, while secondary analysis index was the incidence of anastomotic bleeding, incision infection, and anastomotic stenosis. A comprehensive literature search was performed utilizing the databases Cochrane Library, Embase, PubMed, and Web of Science. We recorded Risk ratios (RRs) and 95% confidence intervals (CI) for each included study, and a fixed-effect model or random-effect model was used to investigate the correlation between TDTs placement and four outcomes after RC surgery.

Seven studies (1774 participants, TDT 890 vs non-TDT 884) were considered eligible for quantitative synthesis and meta-analysis. The meta-analysis revealed that the incidence of AL was 9.3% (83/890) in the TDT group and 10.2% (90/884) in the non-TDT group. These disparities were found to lack statistical significance ( P  = 0.58). A comprehensive meta-analysis, comprising four studies involving a cumulative sample size of 1259 participants, revealed no discernible disparity in the occurrence of Grade B AL or Grade C AL between the TDT group and the non-TDT group (Grade B AL: TDT 34/631 vs non-TDT 26/628, P  = 0.30; Grade C AL: TDT 11/631 vs non-TDT 27/628, P  = 0.30). Similarly, the incidences of anastomotic bleeding (4 studies, 876 participants), incision infection (3studies, 713 participants), and anastomotic stenosis (2studies, 561 participants) were 5.5% (24/440), 8.1% (29/360), and 2.9% (8/280), respectively, in the TDT group, and 3.0% (13/436), 6.5% (23/353), and 3.9% (11/281), respectively, in the non-TDT group. These differences were also determined to lack statistical significance ( P  = 0.08, P  = 0.43, P  = 0.48, respectively).

The placement of TDTs does not significantly affect the occurrence of AL, Grade B AL, and Grade C AL following surgery for rectal cancer. Additionally, TDTs placement does not be associated with increased complications such as anastomotic bleeding, incision infection, or anastomotic stenosis.

Trial registration

PROSPERO: CRD42023427914

Peer Review reports

Introduction

Colorectal cancer (CRC) is the most common malignancy of the digestive tract, with the third highest incidence of all malignancies worldwide and the second leading cause of cancer death [ 1 ].The incidence of rectal cancer (RC) in China has been on the rise [ 2 ]. As part of a comprehensive treatment, RC is currently treated with surgery. Due to the rapid development of Total Neoadjuvant Therapy (TNT), the multimodal approach in the treatment of rectal cancer and various anastomosis and reconstruction techniques in recent years, the treatment of RC with colorectal surgery has made great progress and the incidence of postoperative complications and dysfunction was also significantly reduced in some patients [ 3 ]. Nevertheless, anastomotic leakage (AL), a serious complication, remained prevalent [ 4 , 5 ].

Patients with AL have a poor prognosis, lengthy treatment times, and immense economic and psychological burdens, as well as complications such as peritonitis and sepsis [ 6 ].The occurrence of AL will also contribute to a higher local recurrence rate and a lower survival rate [ 7 ]. The factors influencing AL are not entirely clear at present. Several studies have shown that TDTs placement after the surgery of RC can reduce the risk of AL [ 6 , 8 , 9 ] or Grade C AL [ 10 ], but some studies have shown different results. The placement of TDTs can replace the effect of enterostomy in protecting the anastomosis and avoiding the reoperation, according to some researchers [ 11 ]. However, some researchers believe that TDTs placement will not reduce the occurrence of AL but may also cause anastomotic bleeding and intestinal perforation due to mechanical stimulation [ 6 ]. Therefore, through a systematic review and meta-analysis of TDTs placement and AL after RC surgery in prospective studies, this study further clarified the internal relationship between them, aiming to provide theoretical references for clinical practice.

Materials and methods

Literature search.

A comprehensive search was conducted across four prominent literature databases (Web of Science, Embase, Cochrane Library, PubMed) to identify records published in the English language prior to August 15, 2023. We used the terms "Rectal Neoplasms", "Anastomotic Leak", "Prospective Studies" as subject terms. As free words, I used "Rectum tumor", "transanal tube", "Transanal drainage tube", "Anastomotic Leakage", "Leaks, Anastomotic", "Prospective Study", "Study, Prospective" etc. In order to enhance the efficacy of retrieval outcomes, we integrated the subject term with an unrestricted term. Due to the absence of the subject term "Transanal drainage tube" in PubMed, an unrestricted term search was conducted for the object. To prevent research from being missed, further relevant studies were identified by manually searching references in the online databases and systematic reviews that have been previously published. The literature retrieval processes were comprehensively outlined in Table  1 .

Outcomes of interest and definition

Anastomotic leakage was defined as a defect in the intestinal wall at the anastomotic site that allows communication between the intraluminal and extraluminal compartments [ 12 ]. Grade A AL: Patients are usually free of clinical symptoms and laboratory abnormalities. There is no necessity for therapeutic intervention, as the patient exhibits clinical wellness. Grade B AL: Patients usually have abdominal pain, abdominal distension, and fever, and intra-operatively placed pelvic drains may discharge turbid/purulent or fecal fluid. The patient often needs aggressive interventions such as the implementation of antibiotic therapy, along with the utilization of pelvic drain placement or transanal lavage. Grade C AL: Patients are often quite ill and require operative re-laparotomy [ 12 ]. Anastomotic bleeding was defined as a notable decrease in hemoglobin and active and the presence of ongoing rectal bleeding were not associated with any other cause [ 13 ]. Anastomotic stenosis was defined as the 12-diameter mm colonoscopy cannot passes through the benign narrowing of the anastomosis. Incision infection was defined as an inflammation in the incision and bacterial growth in the incision secretion culture.

Study selection

We used inclusion criteria and exclusion criteria to screen literature related to this study. The following criteria were used to select the studies for the meta-analysis: (1) published as an original article; (2) belonged to prospective study; (3) evaluated the association between the placement of TDTs and the occurrence of AL after RC surgery; (4) given the number of participants.; (5) the risk estimates are presented alongside their respective 95% confidence intervals (95% CI). In the present study, we will proceed to exclude research investigations that are relevant to any of the following categories: (1) Emergency surgery; (2) review paper; (3) animal trials; (4) conference papers; (5) the full text is not accessible; (6) the data cannot be extracted.

Data extraction and quality assessment

The entirety of the articles' content was thoroughly examined during the review process. Data extraction and full-text review were carried out independently based on the preferred reporting items for systematic reviews, A Measurement Tool to Assess Systematic Review 2 (AMSTAR2) and meta-analyses (PRISMA) guidelines by two reviewers and the inconsistencies were rectified by a third author. To eliminate any instances of duplication, the extracted study will be imported into the Endnote Software X9.0, after which the titles and abstracts will be reviewed by two researchers. Furthermore, adherence to the MOOSE (meta-analysis of observational studies in epidemiology) guidelines is recommended [ 14 ]. The collection of data was carried out utilizing standardized forms that were developed by the research team. The information included in the data extraction will be as follows: year of publication, design of study, authors, the quantity of individuals participating in the study. Furthermore, we also conducted an examination of the clinical data and indicators: (1) design of study (Randomized controlled trials vs. Prospective Cohort study vs. Non-randomized controlled trials); (2) case/participants; (3) area (Asia vs. Europe); (4) publication year (≤ 2015 vs. > 2015); (5) quality score (≤ 7 vs. > 7).

Statistical analysis

The meta-analysis was conducted using the Review Manager 5.3 and Stata15.0 software programs. Given that this study obtained binary data from prospective studies, the effect size was determined by employing the risk ratio (RR) calculation. The I 2 index and Cochran's Q tests were utilized to quantify the levels of incoherence and heterogeneity among the studies, respectively. The I 2 index was assessed as a metric for evaluating the extent of heterogeneity across the studies. The data was examined through the utilization of a fixed-effect model in instances where there was an absence of heterogeneity ( P value from the \(\chi\) 2 test > 0.05 and I 2 statistic value < 50%) among studies, while a random-effects model was employed when heterogeneity was present ( P value from the \(\chi\) 2 test ≤ 0.05 and I 2 statistic value ≥ 50%) among studies. To explore potential causes of heterogeneity, sensitivity and subgroup analyses were conducted. Multiple confounding factors were present, including design of the study, quality score, area, and publication year. In addition, sensitivity analyses were carried out to evaluate the robustness of the primary results. Moreover, Egger's correlation tests accounted for the influence of publication bias, and a P value < 0.05 (*) was deemed to be statistically significant [ 15 ].

Search results

From the initial literature, 124 relevant studies were identified (10 studies from PubMed, 21 studies from Cochrane Library, 65 studies from Embase, and 28 studies from Web of Science). The first stage involved the elimination of duplicate articles based solely on titles among predefined databases. Due to duplication, 37 articles were excluded, leaving 87 articles for screening based on titles and abstracts. As well as the 58 studies we excluded, we also excluded studies in animals, case reports, and review articles. 29 studies were reviewed comprehensively. 16 articles were excluded for not reporting relevant results, 2 articles were excluded from the analysis due to unavailability of the full text, and 4 articles were excluded since data was not available. Ultimately, we included 7 articles including 1774 participants between 2006 and 2022 in our meta-analysis [ 4 , 9 , 13 , 16 , 17 , 18 ]. Fig.  1 illustrates the process of literature retrieval.

figure 1

Description of the entire process from literature retrieval to the selection of 7 target articles

Study characteristics, and quality assessment

Table 2 provided a comprehensive overview of the key attributes of the studies that were incorporated. A total of 1774 participants were involved in the 7 studies published between 2006 and 2022. These studies were carried out 1 in Japan, 1 in Denmark, 1 in France, and 4 in China. In addition, 1 was a non-randomized controlled trial, 4 studies were randomized controlled trials, and 2 were Prospective cohort studies. And TDTs placement has no inherent relationship with the occurrence of AL after RC surgery in all studies. Each study successfully adhered to all criteria pertaining to the avoidance of selection and outcome bias.

TDT placement and AL after RC surgery risk

In Fig.  2 , we extracted RRs from 7 studies after multivariable adjustment. We analyzed the data using a random-effects model to compare the association between TDTs placement and the occurrence of AL after RC surgery because of the presence of heterogeneity ( P  = 0.05, \(\mathrm{\rm I}\) 2  = 52%). The meta-analysis revealed that the occurrence of AL was 9.3% (83/890) in the TDT group and 10.2% (90/884) in the non-TDT group. Upon thorough analysis of the combined results from all tests, it was ascertained that there exists no statistically significant association between the placement of TDTs and the incidence of AL following RC surgery (RR = 0.89, 95%CI 0.57–1.37, P  = 0.58). Four studies [ 4 , 9 , 19 ] were identified that reported the occurrence of Grade B AL and Grade C AL, which were subsequently subjected to analysis. Upon analysis of the data on Grade B AL, the outcomes of the heterogeneity test indicated no statistically significant level of heterogeneity ( P  = 0.59, \(\mathrm{\rm I}\) 2  = 0%), thus leading to the adoption of the fixed-effect model. The findings from the meta-analysis indicate that the occurrence of Grade B AL in the TDT group was 5.4% (34/631), which did not exhibit a statistically significant disparity when compared to the 4.1% (26/628) observed in the non-TDT group (RR = 1.30, 95%CI 0.79 -2.14, P  = 0.30) (Fig.  3 ). The heterogeneity test indicated statistically significant heterogeneity in the data on Grade C AL ( P  = 0.09, I 2  = 55%), leading to the adoption of the random-effects model. Similar to the result of Grade B AL, the results of the meta-analysis demonstrate that the prevalence of Grade C AL in the TDT group was 1.7% (11/631), which did not display a statistically significant difference when compared to the (4.3% (27/628) observed in the non-TDT group (RR = 0.52, 95%CI: 0.16 ~ 1.77, P  = 0.30) (Fig.  4 ).

figure 2

A random-effect model was used to analyze the RRs of 7 articles to compare the association between transanal drainage tubes placement and the occurrence of anastomotic leakage after rectal cancer surgery. RR = 0.89, 95%CI 0.57–1.37, P  = 0.58

figure 3

A fixed-effect model was used to analyze the RRs of 4 articles to compare the association between transanal drainage tubes placement and the occurrence of Grade B anastomotic leakage after rectal cancer surgery. RR = 1.30, 95%CI 0.79–2.14, P  = 0.30

figure 4

A random-effect model was used to analyze the RRs of 4 articles to compare the association between transanal drainage tubes placement and the occurrence of Grade C anastomotic leakage after rectal cancer surgery. RR = 0.52, 95%CI 0.16–1.77, P  = 0.30

Subgroup analyses were conducted by area, design of the study, publication year, and quality score (Table  3 ). Initially, a subgroup analysis was performed according to area. The findings from the Asian subgroup (RR = 0.68,95%CI 0.47 ~ 1.00, P  = 0.05), comprising five studies [ 4 , 9 , 13 , 16 , 18 ], indicated that the placement of TDTs effectively prevented AL. Conversely, the results from the European subgroup (RR = 1.61,95%CI 1.03 ~ 2.52, P  = 0.04), consisting of two studies [ 17 , 19 ], demonstrated a significant correlation between TDTs placement and a heightened occurrence of AL. Moreover, the subgroup analyses concerning variables such as the design of study, publication year, and quality score resulted in inconclusive findings ( P  = 0.17, P  = 0.38, P  = 0.92, respectively). Detailed results of the subgroup analysis are presented in Table  3 .

TDTs placement and other clinic outcomes risk

In this study, the correlation between the placement of TDTs and anastomotic bleeding, incision infection, and anastomotic stenosis was further investigated. Due to the lack of significant heterogeneity among the studies, a fixed-effect model was used. Studies found no statistically significant association between the placement of TDTs and anastomotic bleeding (RR = 1.77, 95%CI 0.94 -3.33, P  = 0.08), incision infection (RR = 1.24, 95%CI 0.73 -2.09, P  = 0.43), or anastomotic stenosis (RR = 0.73, 95%CI 0.30 -1.77, P  = 0.48). The comprehensive findings are presented in Table  4 .

Sensitivity analysis

To investigate potential sources of heterogeneity, a sensitivity analysis was conducted. Fig.  5 shows the sensitivity analysis results. Except for any individual study, the collective findings exhibited a range of 0.69(95%CI = 0.56–0.78) to 1.21(95%CI = 1.08–1.42). The findings of the study indicate that the exclusion of a single study did not yield any significant disparity between the combined RR and the total RR. This suggests that the placement of TDTs following RC surgery does not exhibit any correlation with a reduced occurrence of AL. As a result, the main result is robustness.

figure 5

Sensitivity analyses were performed to investigate potential sources of heterogeneity and showed the main result was robustness. The overall results ranged from 0.69(95%CI = 0.56–0.78) to 1.21(95%CI = 1.08–1.42)

Publication bias

To identify the presence of publication bias within the studies that were included, both the Egger test and Egger test plot were employed (Fig.  6 ). The analysis concluded that there was no substantial evidence of publication bias between the placement of TDTs and the occurrence of AL after RC surgery by Egger's test ( P  = 0.10).

figure 6

Egger test and Egger test plot were performed to confirm that there was no significant publication bias between the placement of transanal drainage tubes and the occurrence of anastomotic leakage after rectal cancer surgery. P  = 0.10

Disscussion

Currently, a variety of adjuvant therapy techniques and anastomosis methods are used to treat RC, which results in a higher rate of Sphincter Preserve. However, the incidence of AL after RC surgery is still at a high level. Therefore, a clear understanding of the risk factors and protective factors of AL can bring great benefits to patients. The TDTs is used to drain the proximal intestinal contents and reduce the stimulation of the anastomoses. It can reduce intestinal cavity pressure and the tension of anastomoses. However, there is no consensus on whether the placement of TDTs can reduce the occurrence of AL.

AL following RC surgery cannot be reduced with the placement of TDTs, according to 7 prospective studies in this study. At the level of the original study, according to Tumura [ 16 ] and Zhao [ 4 ] there was no statistical significance between the placement of TDTs and AL, which is consistent with our findings. Meanwhile, the study of Xiao [ 9 ] and Zhao [ 13 ] demonstrated that TDTs placement was a protective factor for AL. Additionally, meta-analyses of the placement of TDTs and AL after RC surgery have had inconsistent results. A meta-analysis of Deng [ 20 ] found that TDTs placement reduced AL incidence in low-risk patients (OR = 0.29, 95%CI = 0.13–0.63, P  = 0.002), but not in high-risk patients undergoing neoadjuvant treatment. The meta-analysis conducted by Zhao [ 10 ]found no significant association between the placement of TDTs and the prevalence of AL. However, it did reveal a reduction in the occurrence of Grade C AL (RR = 0.33, 95%CI = 0.11–1.01, P  = 0.05). The discrepancies in the results between Deng [ 20 ], Zhao [ 10 ], and this study may be attributed to the inclusion of different types of studies and Differences in sample size. Deng [ 20 ] included both prospective and retrospective studies, this study included prospective studies, and Zhao [ 10 ] only included randomized controlled trials. In Guo's [ 21 ] subgroup analysis of the meta-analysis, it was determined that TDTs placement did not exhibit a significant association with the low incidence of AL in randomized controlled trials. However, in observational studies, there was a notable association between TDTs placement and the occurrence of low AL. This finding underscores the influence of study design on the obtained results. Among the seven original papers included by Deng [ 20 ] it is noteworthy that only three of them were prospective studies. Consequently, the divergent conclusion reached by Deng's [ 20 ] study in comparison to the present study can plausibly be attributed to the heterogeneity of results arising from the inclusion of distinct study types. This study exhibits a degree of resemblances to the studies conducted by Deng [ 20 ] and Zhao [ 10 ]. Nevertheless, Deng's [ 20 ] research primarily centers on retrospective studies. The limited evidentiary value of retrospective cohort studies hinders the broad applicability of their findings. Despite the inclusion of the most rigorous randomized controlled trials in Zhao's [ 10 ] study, it was relying solely on three primary research papers. In contrast, this study incorporated seven prospective studies. In comparison to Deng's [ 20 ] study, the prospective studies integrated into this study entail rigorous data quality control during case screening. This practice serves to mitigate the bias arising from case–control studies to a certain degree, thereby enhancing the reliability of the findings. Furthermore, it encompassed a greater volume of original literature and a larger sample size than Zhao’s [ 10 ] study. As a result, this study provides a higher level of evidence and relatively more reliable outcomes.

AL was categorized into one of three grades (Grade A, B, or C) based on its influence on clinical management [ 12 ]. Presently, there is a consensus within the academic community regarding the placement of TDTs to alleviate the severity of AL. When AL ensues, the anal sphincter frequently persists in contracting because of inflammation, pain, and other causative factors. Furthermore, AL frequently manifests during the initial postoperative phase, when the intestinal function has not been restored, and the intestinal contents cannot be eliminated in time, resulting in intestinal high pressure. Physical stimulation caused by high pressure in the intestinal cavity and chemical stimulation caused by intestinal contents is not conducive to the healing of the AL. Drainage of intestinal contents by placing TDTs reduces pressure in the lumen and promotes fecal excretion [ 9 , 22 ], thus promoting recovery of AL. The findings of this meta-analysis indicate that there is no significant correlation between TDTs placement and a reduced occurrence of AL following RC surgery (RR = 0.89, 95%CI 0.57–1.37, P  = 0.58). Considering the following three factors, the relationship between TDTs placement and the incidence of different grades AL was analyzed: (1) Distinct grades of AL necessitate distinct clinical management principles, (2) Grade C AL is of significant concern, as it necessitates a subsequent surgical intervention and escalates the likelihood of restomy and other postoperative complications, (3) TDTs placement can reduce the severity of AL. Given that only four studies in the original literature included recorded the detailed incidence of AL across all levels, it is noteworthy that two out of these four studies did not document the occurrence of Grade A AL. As a result, the present study directed its analysis towards Grade B AL and Grade C AL, while excluding Grade A AL from consideration. The findings of this research indicate that the implementation of TDTs does not result in a decrease in the occurrence of Grade B AL or Grade C AL. Based on the analysis of data from three randomized controlled trials, Zhao’s study determined that the p-value for the association between TDTs placement and the occurrence of Grade C AL was 0.05. Consequently, the researchers of the study of Zhao [ 10 ] reached the determination that the placement of TDTs could potentially yield positive outcomes in mitigating Grade C AL. However, Zhao’s [ 10 ]study did not yield any statistically significant association between the placement of TDTs and the mitigation of Grade B AL. This research group holds a dissenting perspective on the notion that the implementation of TDTs is incapable of diminishing the occurrence of minor Grade B AL, yet it can effectively mitigate the prevalence of severe Grade C AL, while nor does Zhao’s [ 10 ] article offer an explanation for the possible underlying mechanism. As a result, this study augmented the sample size and arrived at an alternative conclusion, namely, the placement of TDTs does not exhibit no correlation with the low occurrence of Grade C AL. This finding suggests that while the placement of TDTs may mitigate the severity of AL, it does not have a significant impact on the occurrence rate of AL.

Furthermore, the present study revealed that the placement of TDTs did not result in a higher occurrence of postoperative complications, including anastomotic bleeding, incision infection, and anastomotic stenosis. The drainage of TDTs, to a certain extent, can support the anastomotic stoma and can be used to detect complications such as anastomotic bleeding and anastomotic infection early, which allows clinicians to take action timely. By using anoscopes and other instruments under direct vision, at the same time, TDTs with moderate hardness was selected, which can minimize the injury of the anastomosis. TDTs of appropriate size and hardness will not cause injury and bleeding of anastomosis. Hence, in cases of AL, the placement of an economical, efficient, and secure TDTs can be employed as a measure to mitigate the extent of AL.

Positive results were observed exclusively in subgroup analysis conducted on area, revealing that TDTs placement served as a protective factor for AL in the Asian group, whereas it posed a risk in the European group. This outcome could potentially be attributed to variations in the study's sample size, discrepancies in the assessment of AL, and the utilization of diverse types of TDTs.

Several factors contribute to AL, and more studies are being conducted to determine the causes and development of AL. It has been confirmed that some factors are closely related to AL's development, such as albumin levels lower than 4 g/dL [ 23 ] and operation time longer than 3 h [ 5 ]. As a common clinical treatment, the placement of TDTs has low technical requirements and is suitable for hospitals of every level. Multiple studies have documented the occurrence of unfavorable incidents associated with the placement of TDTs subsequent to RC surgery, with anal pain being the most frequently reported complication [ 4 ]. Due to the lack of comprehensive documentation regarding adverse events following TDTs placement in the original literature included in this meta-analysis, statistical analysis pertaining to such events was not performed in this study. The visual analogue scale was employed to assess the pain perception experienced by the patients, which is also suitable for the assessment of anal pain after the placement of TDTs. The score ranges from 0 to 10, where 0 denotes the absence of pain and 10 signifies the most severe pain that can be imagined [ 24 ]. The pain was subsequently categorized into four distinct levels. No pain: score of 0, indicating the absence of pain; Mild pain: score of 1–3, representing pain that is tolerable; Moderate pain: score of 4–6, indicating pain that may disrupt sleep but remains tolerable; Severe pain: score of 7–10, signifying pain that is unbearable. A randomized controlled study found that TDTs placement caused anal pain in 46.4% of patients, moderate pain in 3.9%, and unbearable pain in 3 patients [ 4 ]. What's more, other studies have documented iatrogenic perforation resulting from the placement of TDTs [ 6 , 25 ], as well as cases necessitating emergency laparotomy due to such perforations [ 25 ]. In addition, studies have reported that no expected drainage effect occurs after the placement of TDTs, manifested as fecal discharge from the anus rather than from the TDTs [ 4 ].Despite the lack of correlation between the placement of TDTs and the occurrence of AL after RC surgery. However, it is considered that the placement of TDTs can reduce the severity of AL, and healthcare professionals can enhance patient outcomes by proactively optimizing preoperative nutrition, limiting surgical duration to a maximum of three hours, and implementing the placement of TDTs following AL. The placement of TDTs helps to discharge the intestinal contents in time, which is conducive to reducing the length of hospital stay. Studies have found that patients with high-risk factors for anastomotic leakage, such as diabetes and open surgery, have a higher probability of readmissions within 30 days [ 26 ]. The placement of TDTs positively affects the timely and rapid detection of intestinal abnormalities. Thus, the disease can be treated earlier and the reoperation rate can be reduced.

There are several strengths of this meta-analysis: All relevant prospective studies ( n  = 7) from recent years with rich data and high statistical power were included. In addition, our study included recently published randomized controlled trials and more participants ( n  = 1774) than previous meta-analyses. Finally, a sensitivity analysis was performed to assess the potential influence of utilizing adjusted risk ratios on the aggregated effect estimates.

There remain certain limitations within this study. Primarily, the present meta-analyses were unable to mitigate heterogeneity, whether in the overall population or in subgroup analyses. Furthermore, while gender and age are commonly recognized as confounding factors in numerous studies, there exist additional variables that may also hold significant importance, such as the type of TDTs, presence of diverting stoma, and utilization of Neoadjuvant therapy, which may also possess considerable significance. However, none of these phenomena have been thoroughly investigated. The third aspect pertains to the highly intricate and diverse nature of AL. The existing model is incapable of mitigating this heterogeneity. Fourth, the sample size of some included documents is small, and the statistical impact may exhibit constraints, thereby posing challenges in terms of generalizability of the findings.

Conclusions

In conclusion, the placement of TDTs does not yield significant results in terms of reducing the occurrence of AL after RC surgery, including Grade B AL, and Grade C AL. Furthermore, TDTs placement does not lead to heightened complications such as anastomotic bleeding, incision infection, or anastomotic stenosis. Based on the potential for anal pain, iatrogenic perforation, and limited efficacy associated with TDTs placement, we advise against the immediate placement of TDTs following RC surgery. The findings of this research are derived from a compilation of seven prospective studies. Given the current scarcity of data and the variability observed among studies, the conclusion remains subject to scrutiny. Consequently, future investigations should prioritize the implementation of meticulously planned randomized controlled trials with substantial sample sizes to corroborate this assertion.

Availability of data and materials

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Abbreviations

  • Transanal drainage tubes
  • Anastomotic leakage
  • Rectal cancer

Risk ratios

Confidence intervals

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This work was supported by the Hebei Provincial Natural Science Foundation precision medicine joint project (H2020206485) and Hebei Provincial Department of science and technology key project (206Z7705G).

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Yating Liu and Xuhua Hu contributed equally to this work and co-first authors..

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Department of Gastrointestinal Surgery, the Third Hospital of Hebei Medical University, Shijiazhuang, P.R. China

Yating Liu, Yu Huang, Xu Yin, Pengfei Zhang, Yaoguang Hao & Hongyan Li

The Second General Surgery, the Fourth Hospital of Hebei Medical University, Shijiazhuang, P.R. China

Department of Gastrointestinal Surgery, the Second Hospital of Hebei Medical University, Shijiazhuang, P.R. China

Guiying Wang

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Yating Liu, Xuhua Hu, Hongyan Li, and Guiying Wang contributed to the conception and design of the study. Yating Liu, Yu Huang, Xu Yin, Pengfei Zhang, and Yaoguang Hao acquired and analyzed the data. Yating Liu and Xuhua Hu drafted and revised a significant portion of the manuscript or figures. Xu Yin and Yaoguang Hao conducted the statistical analysis. Yating Liu, Xuhua Hu, and Yu Huang wrote the paper. All authors read and approved the present version of the manuscript to be published.

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Liu, Y., Hu, X., Huang, Y. et al. Does transanal drainage tubes placement have an impact on the incidence of anastomotic leakage after rectal cancer surgery? a systematic review and meta-analysis. BMC Cancer 24 , 263 (2024). https://doi.org/10.1186/s12885-024-11990-8

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