Systematic Reviews & Meta-Analysis

Study selection (also known as screening) is the process where all the studies and articles identified during your systematic search are reviewed to be included or excluded based on the inclusion/exclusion criteria in your protocol.

Prior to beginning the screening, all search results from your chosen databases and sources should be exported to either a reference management software (EndNote, Zotero, etc.) or an excel document. There may be duplicate records, so it’s best to remove these so that no single article is reviewed twice.

There are two phases of the screening process, the first being title/abstract screening and the second being full-text screening. More details about each phase are described below.

In the Title/Abstract screening stage, each reviewer will need to scan titles and abstracts to see if they match the eligibility criteria or have some value to the systematic review. This is done separately by each reviewer to ensure minimal bias. Often the large majority of search findings is rejected at this step.

1. Each title/abstract is screened to see if they meet the inclusion/exclusion criteria established in the protocol phase of the systematic review. At least two reviewers will conduct the screening. Each reviewer will independently review each title/abstract and assigned one of the following decisions:
   • Yes (the title/abstract looks relevant)
   • Maybe (the title/abstract may be relevant; there is not enough detail to confirm either way)
   • No (the title/abstract is clearly not relevant)
2. The decisions are tallied and compared.
3. Any discrepancies can be resolved by either: a) discussion and consensus, or b) by a third independent reviewer.
4. Records with a Yes or Maybe will move on to the Full-Text screening stage.

In the Full-Text screening stage, each reviewer looks through the full-text of included articles to fine-tune the final collection of articles that will contribute to the review

1. Each full-text articles is screened to see if they meet the inclusion/exclusion criteria established in the protocol phase of the systematic review. At least two reviewers will conduct the screening and provide one of the following decisions:
   • Yes (the study meets all inclusion criteria and should therefore be included)
   • No (the study does not meet all inclusion criteria, or meets one of the exclusion criteria and should therefore be excluded)
2. Any exclusions should be recorded and given a reason in order to be reported at a later time.
3. The decisions of reach reviewer are tallied and compared.
4. Any discrepancies can be resolved by either: a) discussion and consensus, or b) by a third independent reviewer.

Reviewing and selection of studies is a time-consuming phase of the systematic review process. The following tools offer a variety of assistance in the screening process including keeping track of decisions, de-duplication, and extracting abstracts from databases and reference management software.