What is screening?

You've now conducted all your searches and have a lot of papers to go through - some of them you can already see don't really answer your research question.

Screening is the process where you select the studies from the literature which will be included in your review. Each individual article must be assessed to see if it meets the inclusion criteria you've set out in your protocol.

PRISMA (Preferred Reporting Items for Systematic reviews and Meta-Analyses) has been described before, but as it is fast becoming a standard for reporting of systematic reviews and meta-analyses (and other review types), it's worth mentioning again here. It includes a procedural checklist, and a flow diagram to illustrate the screening process. 

Consider also using one or more of the tools described on the Managing Your Review page of this guide:

• EndNote - If all your searches have been exported into an EndNote library, you can create groups to screen citations against inclusion and exclusion criteria and then populate the PRISMA flow diagram. You can also use EndNote in conjunction with SUMARI or Rayyan. Have a look at this article which gives some great tips on using EndNote for systematic reviews:

Peters, M. D. (2017). Managing and coding references for systematic reviews and scoping reviews in EndNote. Medical Reference Services Quarterly, 36(1), 19-31. doi:10.1080/02763869.2017.1259891

• JBI SUMARI - Subscribed to by CSU and facilitates the whole systematic review process, including blind screening. (Follow the instructions here if you haven't accessed it before).
• Rayyan  - free software which facilitates team screening, including the upload of citations and  recording of the decisions behind the screening process.

The reviewing team

To reduce the risk of selection errors or bias, you should have at least two reviewers (including yourself) to screen your search results. Your reviewers should:

• have a good knowledge of the topic so they can work quickly and accurately
• have a thorough understanding of the inclusion and exclusion criteria developed in your original review protocol
• screen independently to avoid influencing each other as they work

Two stages of screening

1. Title/Abstract screen: This is when the titles and abstracts of each article are scanned to remove obviously irrelevant studies. At this stage you may not need to provide a justification for your exclusions, and some papers may remain undecided. Think about your review question. For example:

• Does the article cover the right population?
• Does it cover the type of intervention set out in the review question or protocol?
• Is the outcome the one being examined in your review?

2. Full text screen: Here you need to locate the full text of the non-excluded studies and carefully examine each one for compliance with your eligibility criteria. Now the reviewers should document the reason for excluding any articles.  

Your review paper should provide details of how many reviewers screened the articles and how any disagreements were resolved. This is usually in the methods section.

For more information check our library resources on systematic reviews, and also The Cochrane Handbook, Part 2, 7.2 - Selecting studies