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Systematic Reviews

This guide provides information and resources about systematic reviews, meta-analyses, and other literature reviews.

Steps of a Systematic Review

An evidence synthesis protocol states your rationale, hypothesis, and planned methodology. Much like a blueprint for a house, a protocol outlines the planned framework for the evidence synthesis. Members of the team use the protocol as a guide to conduct the research. It is recommended that you register your protocol prior to conducting your review. This will improve transparency and reproducibility, reduce bias, and will also ensure that other research teams do not duplicate your efforts. A protocol template and checklist are included on this page, as well as a checklist for structured literature reviews that serves as a similar document to an evidence synthesis protocol.

  • Evidence Synthesis Protocol Template
  • Planning Worksheet for Structured Literature Reviews
  • PRISMA Checklist
  • PRISMA Extension for Scoping Reviews
  • PRISMA Extension for Network Meta-Analysis

When beginning a systematic review, the review team must develop a clearly defined research or clinical question and determine the inclusion and exclusion criteria for the selection of articles for the review.

Once the review team has developed the question, it is recommended that the team search for existing published reviews on the topic. If there are already one or more systematic reviews published on your topic, then it is not necessary to conduct an additional review on the same topic. Also, reviewing previously published systematic reviews can assist your research team in reframing your question as needed.

Be sure to save any research articles that align with your topic. These articles can be used as examples when developing your search strategies for the review (see Systematic Search tab).

Resources for Locating Existing Systematic Reviews:

  • PubMed: Filter searches using the "Systematic Reviews" filter under "Article Types" to view reviews on your topic, remove filter to view all types of research articles
  • Cochrane Library: Click on the "Cochrane Reviews" tab to locate Cochrane Reviews on your topic
  • TRIP: Free resource to locate systematic reviews on various topics

Inclusion and exclusion criteria are developed after a research question is finalized but before a search is carried out. They determine the limits for the evidence synthesis and are typically reported in the methods section of the publication. For unfamiliar or unclear concepts, a definition may be necessary to adequately describe the criterion for readers.

Selecting Databases

Which databases you include in the development of your review depends on your research question and the discipline areas in which your research question is related. Your subject librarian(s) can recommend relevant databases. Check out UT Libraries' research guides or database catalog for a full list of available sources across all disciplines provided by the university.

Remember every database works differently. Your subject librarian(s) can assist with designing complex searches using the specialized syntax of individual databases and 'translate' searches between databases. Consult with your subject librarian(s) if you have questions.

The systematic search serves as the foundation for the review's data collection process. Systematic searches must be comprehensive and exhaustive to capture every published and unpublished article about the review topic to reduce the risk of bias.

Systematic searches should include:

  • Multiple databases (such as PubMed, CINAHL, Scopus, and Web of Science)
  • Grey literature resources (such as, OpenGrey, and Grey Literature Report)
  • Comprehensive search terms that can be reproduced within respective databases and clearly reported for transparency
  • Numerous search results (review team will need to commit significant time toward reviewing review articles for inclusion/exclusion)

Many systematic review experts recommend that review teams collaborate with librarians or informationists to create comprehensive and reproducible searches for selected databases and grey literature resources. Please see the Library Support section for more information about how our Subject Librarians can assist with the search process.

Boolean Operators

Using Boolean logic is also an important component of writing a search strategy:

  • "AND" narrows the search, e.g. children AND exercise
  • "OR" broadens the search, e.g. (children OR adolescents) AND (exercise OR diet)
  • "NOT" excludes terms, e.g. exercise NOT diet
  • "*" at the root of a word finds all forms of that word, e.g. (child* OR adolescen*) AND (exercise* OR diet*)
  • Parentheses "( )" ensure all terms will be searched together as a set quotations around a phrase searches that exact phrase, e.g. (child* OR adolescen* OR "young adult*")

Registering your protocol that you developed for your systematic review is an important step in the review process. The creation and registration of a systematic review protocol help to reduce the unnecessary duplication of reviews, enhance transparency, and reduce publication bias

The protocol creation process involves outlining a detailed plan for your review, including your study question, database selection, inclusion/exclusion criteria, and methods for data analysis and article bias assessment. 

For more information on creating and registering protocols, please review the following resources:

You may also review our Protocol Resources section for more information.

Evidence synthesis methods require authors to search multiple databases, and not all databases accept the same search "syntax." Each individual database requires the use of specialized search syntax, and therefore evidence synthesis search strategies must be 'translated' between databases.

For example, a search for vitamin D[tiab] in PubMed will show you all citations with the phrase "vitamin D" in the title, abstract, or keywords, but a search for vitamin D[tiab] in Web of Science will not work at all.

Contact your subject librarian(s) for assistance with search syntax translation. See the Library Support section for more information about how our Subject Librarians.

The review of studies can be the most time-consuming step within the systematic review process. Review team members will need to review each article abstract for the initial determination of whether each article should be included in the review based on pre-determined inclusion/exclusion criteria. The review team will also need to resolve any conflicts that arise during this abstract review stage.

Once abstracts are reviewed, included abstracts will move into the full-text review stage. The review team will need to compile the full-text articles or PDFs and evaluate each article using the same pre-determined inclusion/exclusion criteria during the abstract review stage. Conflicts arising from this stage will also need to be resolved by the review team.

The review team should document these review steps and totals using the PRISMA 2020 Flow Diagram for inclusion in the written report.

Please refer to the Screening Tools and Citation Management sections for valuable tools to assist with this process.

The data extraction and analysis portion of the systematic review process is another time-intensive component for the review team. Team members will extract relevant data from included studies for further analysis. The review team will also need to perform a quality and bias assessment of the methodologies used within the included studies using validated tools. 

For more information regarding data extraction, please review the following resources:

Risk of Bias Assessment

Risk of bias assessment (also sometimes referred to as "quality assessment" or "critical appraisal") establishes transparency of evidence synthesis results and findings. A risk of bias assessment is often performed for each included study in your review in order to eliminate bias in the findings. Individual studies that are included in a review may include biases in their results or conclusions; this could include design flaws that raise questions about the validity of findings or an overestimate of the intervention effect. Risk of bias assessment generally is only required for systematic reviews. However, this may depend on the evidence synthesis method that you are utilizing.

Risk of Bias Assessment in a Discipline Outside of Human Medicine

This Cochrane Training presentation helps to navigate the steps of Risk of Bias Assessment, but some things might not apply to other disciplines. For disciplines outside of human medicine, the Critical Appraisal Skills Programme provides checklists that can be applied to a diverse array of study types, and the Mixed Methods Appraisal Tool can be a helpful resource if included studies use mixed methods.

The most valuable part of the systematic review process is the dissemination of the review findings through the written report. The review team will benefit from identifying targeted journal(s) for publication and following the author and submission guidelines of those journals for the written report. It may also help the review team to read other systematic reviews from their targeted journals for examples of how to format the written report.

For assistance with identifying possible journals for the submission of your written report, please review the resources below: