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Systematic Literature Review

Overview of Systematic Literature Review (SLR)


Steps in the process

Define the research question

Look for existing reviews on your topic and identify gaps in the current literature to help to develop your question.This will also ensure that you are not duplicating previous reviews.The question should be clear and unambiguous, and the objectives should also be stated. Consider using a framework to help draft your question.  For example PICO, PEO, SPIDER, SPICE or ECLIPSE, this will also help you to develop a comprehensive search strategy.  When you have set your protocols you should register your review.

The following databases can be used to check for other reviews.

Provides access to, and guidance on conducting, high-quality systematic reviews in the area of health. Founded in the United Kingdom in 1993, it now has members in 130 countries.

Provides similar information to Cochrane but focuses on social and behavioural sciences, including education, crime and justice.  Founded in the United States in 1999, it now has member in over 13 countries.

Prospero aims to provide a comprehensive listing of systematic reviews registered at inception to help avoid duplication and reduce opportunity for reporting bias by enabling comparison of the completed review with what was planned in the protocol. (Description taken from website)

Develop your protocol.  Your protocol should include your hypothesis or research questions and detail how the review will be conducted. It should also state the minimum standard that studies must reach to be included in the review.  The criteria for inclusion and exclusion must be clearly defined. Use of a framework will also help with this step.

Design a comprehensive search strategy.  You will need to search a number of different databases. Your search will be extensive.  Including electronic and printed sources. Remember to include any specialist databases and use the relevant subject headings within each database. Searches across different databases need to be consistent, so use a recognised search filter to narrow your search.  For example, from TASC or the BMJ Clinical Evidence Study Design Search Filter.  Save all references in bibliographic management software (Endnote, Mendeley, Zotero, etc.), this will help you to remove duplicates.

Select studies.  Use the agreed inclusion/exclusion criteria to ensure consistency (see search strategy).  

Extract and synthesize the data by tabulating the characteristics, themes or categories, such as methodologies and effects in each study.  You can do this by using a spreadsheet or specialist software such as Covidence, Rayyan, DistillerSR or Eppi Reviewer (some software will require a subscription fee).

Check for Bias.  Use Cochrane’s Risk of Bias (RoB) tool to help with this process.

Analyse and present results clearly, include a detailed methodology of your search strategies and your selection criteria.  Depending on the purpose of your review, your tabulation of information may allow you to do a meta-analysis of studies, which could provide evidence-based guidelines for future practice or policy.

You should Identify and discuss shortcomings and limitations.  Highlight any contradictions and identify how these could be resolved in the future.  Be sure to contextualize your findings relative to the existing knowledge in the subject.

Reporting guidelines ensure consistency and transparency throughout the review process.  For example, PRISMA or Equator-Network.