The process of screening is to make sure studies in the review are actually relevant to the research question. Many times search results yield unrelated content that must be sifted out to make sure only the highest-quality evidence remains that sticks to the protocol criteria. Keep in mind that the screening process can be extremely time consuming and resource intensive.
Basic steps for inclusion and exclusion
- The review process for inclusion and exclusion should be applied by at least 2 reviewers to all the studies retrieved by the literature search. A third screener should be considered to resolve any disagreements between the reviewers and should be outlined in the protocol.
- Consider using Systematic Review tools/software to make the screening process easier. At present, Drexel University Libraries does not offer a subscription or access to these tools.
- However, citation management tools like EndNote and Zotero can also be used in placed of SR software to download and organize results.
- The first level of screening involves scanning the titles and abstracts of the articles. Any articles that are irrelevant can be excluded.
- The second level of screening will be for full text articles and they must be obtained. The library may have the full-text PDFs, but some articles might need to be placed for an interlibrary loan. Those articles that meet the criteria are included in the review. Remember to keep track of the reasons for exclusion of articles. It must be documented since it will have to be recorded and represented on a PRISMA flow diagram.
Things to consider as part of the screening process
- Transparency - have pre-specified eligibility for inclusion and exclusion criteria to reduce bias and provide reproducible results. This is explicit in the protocol.
- Quality - Screening can be used to eliminate low-quality or poorly designed studies, which may introduce bias and lead to misinterpretation of review findings.
- Relevancy - Only studies addressing the research question are included in the review. Irrelevant studies are removed or excluded.
Reducing Bias
Sometimes published SRs will exclude studies if they do not fit a specific study designs, are written in languages other than English, or written within a certain time frame. Keep in mind to be cautious of any bias that could be introduced into the review by adding certain inclusion or exclusion criteria. As an example, if one limits to studies in English there is a possibility that important studies published in other languages are omitted, leading to language bias.
