Once results have been deduplicated, you will begin the screening process. This is where you'll apply your eligibility criteria to each result. While strict systematic review methodology requires all eligibility criteria to be defined a priori (in advance), some research synthesis approaches allow for ad hoc (as you go) criteria based on the researchers' increasing familiarity with the available research. Just be sure to document if your approach shifts!
Screening often happens in two steps.
- Title and abstract level screen to exclude studies that are clearly outside the study parameters.
- Full text screening for those studies identified in Title/Abstract screening. Some do the coding and data extraction during this second screening stage.
For comprehensive evidence synthesis projects, it is important to have two people screening each item, with the process blinded so that each person is making a decision independently. If the two people make conflicting decisions, then the disagreement is resolved by consensus-based discussion or by a third screener.
Recommended Tools:
- Rayyan - Rayyan is a free and open sources screening tool.
- When screening, you can view the title and abstract of each record; blind the process so that your decision cannot be seen by other members of the team; add keywords that will be highlighted in the title and abstract to aid you in making decisions - usually these are keywords related to your inclusion and exclusion criteria; use the choices in the "reason" menu to indicate the reason for your decision; add a note; etc.
- When finished with the title/abstract screening stage, you can export a file with all "included" studies, and then upload into a newly created Rayyan project for the full text screening stage. Uploading the PDF of each article to each record in this second stage is a convenient option.
- Covidence - If your team invested in this fee-based product, you will see the following features: the screening process is blinded between members of the team; exclusion and inclusion criteria can be loaded into the tool so that you can view them while screening; records with yes decisions from the title/abstract screening stage will automatically be pushed to the full text stage screening stage; full text articles can be batch uploaded for the full text stage; the PRISMA flowchart is automatically populated based on the decisions made in each screening stage, etc.
- Excel - This is the most basic tool for the management of the screening process. Lists of references complete with abstract can be exported from citation managers into Excel format for screening. You can create individual columns for each screener where they will mark their decision. Blinding will be by honor system.
Other Options:
- Systematic Review Accelerator: Screenatron and Disputatron. This is a free tool that runs locally on individual computers. Each screener works individually on their own pool of studies in the Screenatron tool. Once each screener completes their screening, they export their decisions into the Disputatron to identify and resolve disputes. Instructions available here.
Articles reviewing screening tools:
Harrison H, Griffin SJ, Kuhn I, Usher-Smith JA. Software tools to support title and abstract screening for systematic reviews in healthcare: an evaluation. BMC Med Res Methodol. 2020 Jan 13;20(1):7. doi: 10.1186/s12874-020-0897-3. PMID: 31931747; PMCID: PMC6958795.
Van der Mierden S, Tsaioun K, Bleich A, Leenaars CHC. Software tools for literature screening in systematic reviews in biomedical research. ALTEX. 2019;36(3):508-517. doi: 10.14573/altex.1902131. Epub 2019 May 16. PMID: 31113000.
