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Systematic Reviews: Study Selection (Screening)

Created by Health Science Librarians

Role of the librarian in this stage

A librarian can advise you on study selection for your systematic review, including: 

  • How to use Covidence to screen citations and manage the screening process
  • How to apply your review inclusion and exclusion criteria to the screening process

Contact HSL About Your Review

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Ready to start a systematic review? HSL Librarians can help!

Fill out the Systematic Review Request Form and the best-suited librarian will get back to you promptly. Our systematic review service is only available to faculty, staff, students, and others who are affiliated with UNC Chapel Hill.

Screening Results for a Systematic Review

Once you have completed literature searching and compiled all citations, it is time to screen the results. The purpose of screening is to eliminate studies that do not meet your inclusion criteria. Two independent reviewers should screen all studies, starting with a title and abstract screening, followed by a full-text screening. A third reviewer should resolve any conflicts. 

Helpful Tip - Preliminary Testing and Screening

One of the most important aspects of screening citations is to make sure the team adequately understands how to properly apply the inclusion and exclusion criteria to the citations being screened. It can be especially helpful for screeners to undertake preliminary/test screening on a subset of articles to ensure agreement. Test screening can be performed in Covidence or Excel. While adding this step may add some time initially, it will most likely expedite both screening phases after as screeners will be more comfortable applying the inclusion and exclusion criteria properly and most likely result in less error or conflicts.

Reporting Standards for Systematic Reviews (PRISMA)

"PRISMA stands for Preferred Reporting Items for Systematic Reviews and Meta-Analyses. It is an evidence-based minimum set of items for reporting in systematic reviews and meta-analyses. The aim of the PRISMA Statement is to help authors improve the reporting of systematic reviews and meta-analyses. The PRISMA Statement consists of a 27-item checklist and a four-phase flow diagram." (From prisma-statement.org )

In your review, you will need to track the number of results from each database you search, the number of duplicates you remove, the decisions you make on each article, and in the full text level, the reasons why you exclude articles. More information and a step-by-step guide can be found on the Using PRISMA for Reporting page on this guide.

Screening Tools

There are many tools that can be useful for organizing the screening process including Covidence, Rayyan, Abstrackr, and HAWC.   

UNC currently has an institutional subscription to Covidence making it available for free to UNC-affiliated users. HSL can provide classes and support for Covidence. To learn more visit the Covidence LibGuide. HSL does not currently offer in-house support for other screening tools; however, links to training materials are provided directly below.  

All of these tools support reference importing of multiple file types (.ris & txt), in-/excluding references, exporting results, and tagging with keywords. Additionally, they are all web-based and therefore can be used on a mac or pc. They cannot assist with protocol development or automated searching. The chart below provides more details to help you compare and choose a screening tool.

The table compares Covidence, Rayyan, Abstrackr, and HAWC (from left to right) based on a number of features.
Feature: Covidence Rayyan Abstrackr HAWC
Logo Covidence Logo Rayyan Logo abstrackr Logo HAWC Logo
Cost UNC has a subscription to Covidence Free Free Free
Support available at UNC HSL Yes No No No
Quality Assessment Yes Yes No Yes
Data Extraction Yes  Yes No Yes
Allows Multiple User Support Yes Yes No No
Reference Allocation Yes Yes Yes No
Multiple Screening Phases Yes No No No
Discrepancy Resolving Yes Yes Yes No
Show Project Progress Yes Yes Yes No
Attaching Comments Yes No Yes No
Attaching PDFs Yes Yes No Yes
Keyword Highlighting Yes Yes Yes No
Deduplication Yes Yes No No
PRISMA Diagram Yes No No Yes
Interrater Reliability Yes Yes No No
Mobile Friendly Version Yes Yes No No
Export Results File Types RIS, CSV, TXT RIS, BibTex, CSV, EndNote RIS, CSV, XML XLSX

If the tools above don't meet your needs, you can also try this Excel tool called the VonVille Method.  

Information about screening tools and features:Van der Mierden, S., Tsaioun, K., Bleich, A., & Leenaars, C. H. C. (2019). Software tools for literature screening in systematic reviews in biomedical research. ALTEX : Alternativen zu Tierexperimenten, 36(3), 508-517.

Quality Assessment: The tool supports risk of bias and quality assessment. 

Data Extraction: The tool supports data extraction. 

Allows Multiple User Support: It is possible for two or more users to work on the same project at the same time, without seeing how others have voted.

Reference Allocation: It is possible to assign references to reviewers. 

Discrepancy Resolving: There is official support for resolving conflict between reviewers. 

Show Project Progress: the tool can display the progress of each reviewer and the overall project.

Attaching Comments: It is possible to add comments to a reference while screening.

Attaching PDFs: It is possible to upload PDFs for full-text screening. 

Keyword Highlighting: It is possible to to display highlighted keywords during screening.

Deduplication: The tool will identify and remove duplicate citations. 

PRISMA Diagram: The tool can automatically generate a PRISMA flow diagram. 

Import Multiple file Types: It is possible to import formatted references and the tool supports multiple file types. 

Interrater Reliability: The tool can calculate and display interrater reliability.

Mobile Friendly Version: It is possible to screen on a mobile device. 

Export Results File Types: References can be exported from the screening tool into the listed file types.