Systematic Reviews: Search Criteria

Because search criteria and the search strategy used will be part fof the Methods section of your published paper. It must be described in sufficient detail so that a reader could reproduce the search. 

The decisions incorporated into your search criteria can increase or decrease the likelihood of getting your systematic review project published. Remember that the goal of any systematic review is to produce the highest possible evidence. Therefore, frivolous or arbitrary criteria can be criticized. A search strategy that is overlooking possible relevant sources or missing key concepts may be rejected.

The search criteria and strategy is intended to be comprehensive and retrieve ALL relevant studies while minimizing bias. This will retrieve A LOT of sources that will be narrowed down but the research team to only the few relevant studies.

And keep a record of where and how you searched. It will make your project reproducible and it will increase its credibility.

Search for clinical trials for results that are not statistically significant. They are less likely to be published as journal articles.

Search for conference presentations.

Be critical of the inclusion/exclusion criteria of your own project. Other researchers will be. Are you using the most appropriate criteria possible to maintain the high quality of the final product?

• Time periods.  Is excluding sources due to time period appropriate? If you wish to establish a time period, such as no publication older than X years, is there a good argument and justification for that cut off? What if a relevant study is one year outside of your time period? Would you exclude it and can you defend that exclusion? Reviewers might criticize seemingly random limits for time.
• Languages. Google Translate and other applications have made language barriers less of an obstacle. Also, diversity/equity/inclusion issues make it less desirable to exclude studies solely due to their language.
• Geography or Location Does your research question require your team to include or exclude specific locations of the world? Does it apply to only certain populations?
• Age, Gender Ethnicity. Does your research question require you to include or exclude specific age groups, gender, or ethnicities? Is this for the protection of that group? Also, diversity/equity/inclusion issues make it undesirable to exclude groups unnecessarily.
• Methodologies and Study Designs. Typically, only original studies are acceptable for a systematic review. What methodologies are acceptable for your research question? SRs only accept study designs that rank as high quality evidence. Qualitative SRs also require a determination of acceptable methodologies to avoid comparing apples to oranges in the findings of the SR. 
• Comprehensive Search Plan. The search will retrieve a very large number of studies. Can your institution and its library support getting the full-text? Is your team prepared to invest the time required to evaluate the records? To evaluate the narrowed list of relevant studies?

Search for studies that have not been formally published. Conference papers, reports, white papers. etc. SR researchers want to find every legitimate study on their topic wherever it may be.