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.

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

• 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 range of flow diagrams to illustrate the screening process. 
• 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 and scoping 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 Charles Sturt and facilitates the whole systematic review process - from drafting your protocol to study selection, critical appraisal, data extraction and synthesis. You can invite other reviewers and researchers to your project.
• Rayyan  - This free software facilitates team screening, including the upload of citations and recording of the decisions behind the screening process.
• Covidence - Produced by Cochrane, this SR software is highly respected and available for individual subscription through their website. A trial version is available for reviews with 500 citations or fewer.

After you have run your search in the chosen databases, you will need to remove duplicates from your complete list of results (this can be done in EndNote). Then begins the work of going through the results to find the most rigorous and appropriate to help answer your research question.

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, Chapter 4.6 - Selecting studies