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Systematic Reviews: Selecting Studies

The Basic Process

At least two team members must independently evaluate all the studies to prevent bias.

There are two rounds of review. 

  1. TITLE/ABSTRACTS:  In the first review, members vote on whether to include/exclude each study based solely on the titles and abstracts. There is no need to record the reasons why studies were excluded. After both team members have evaluated the studies, votes are compared and differences are settled in a pre-specified way. 
  2. FULL-TEXT:  In the second round of reviews, members evaluate the remaining studies by the full-text articles. Members must record the reasons for excluding studies based on the pre-determined inclusion/exclusion criteria they chose when planning the review. After both team members have evaluated the studies, votes are compared and differences are settled in a pre-specified way. 

Usually only a very small percentage of the initial documents retrieved are included in the final systematic review. Common estimates range from 1-3%.

Establish Inclusion/Exclusion Criteria

Criteria will vary depending on your research question.

Recommended Inclusion Criteria: for reviews about treatment, diagnosis, etiology, and more.   

Software for Selecting Studies

  • Rayyan - a free online tool that screens, analyzes, and extracts data. You can can export citations from EndNote or directly from the databases themselves. It is easily shareable among several reviewers and allows independent title/abstract screening and coding. It uses tagging and filtering to code and organize references. screen, analyze, and extract data from systematic reviews. Rayyan also has a free mobile app (iOS/Android).
  • Covidence easily sharable among several reviewers and allows for independent title/abstract screening, full text screening, data extraction, and risk of bias assessment. It is now required by reviewers doing Cochrane systematic reviews. It currently allows a free trial to do a single review shared between two reviewers.
  • DistillerSR - allows for the management of the entire systematic review process with multiple independent reviewers. Requires a monthly subscription fee.

Record Selection Process

PRISMA 2020 Flow Diagram

10 minute Introduction to PRISMA

PRISMA Flow Diagram Generator (more complex diagrams in various formats (gif, jpg, pdf, etc).