Evidence Synthesis Guide : Grey Literature Searching

The Mayo Clinic Libraries' systematic review search Request Form asks the requestor whether the librarian should include conference abstracts in the search results. "Cochrane and the United States National Academy of Sciences (NAS) both recommend always searching for and including conference abstracts in systematic reviews."¹ Including abstracts in the search results helps mitigate publication bias by ensuring that data otherwise unpublished are captured in the review of the literature.

There are arguments against including conference abstracts in a systematic or knowledge synthesis review. Due to their brief nature, abstracts frequently lack adequate information regarding the study's design, methods, risk of bias, outcomes, or results; the review team must search for the full-length published paper (usually published following the conference) or contact the authors to obtain the information required for critical appraisal of the study. Additionally, the quality of the research presented in conference abstracts may be called into question. Many abstracts report preliminary/incomplete study results and are not peer-reviewed.

Scherer and Saldanha¹ provide a flow chart for decision making regarding whether to include conference abstracts in a systematic review. Review teams must recognize how the inclusion or exclusion of conference abstracts affects the outcome of their review. Including conference abstracts may require extra effort on the part of the team, but excluding them results in the potential for bias.