Adherence to the PRISMA-P 2015 reporting guideline was inadequate in systematic review protocols.

Objectives: The objective of the study was to investigate to which degree systematic review protocols adhere to the Preferred Reporting Items for Systematic review and Meta-Analysis Protocols (PRISMA-P) reporting guideline.

Study Design And Setting: We randomly sampled 50 publications of systematic review protocols indexed in PubMed and 50 protocols uploaded to the International Prospective Register of Systematic Reviews (PROSPERO) from 2016 onward. Two authors independently extracted data and assessed adherence to the 26 items specified by PRISMA-P. For each protocol, we categorized adherence to PRISMA-P as complete (≥90% of PRISMA-P items were fully reported) or partial (≥60% of PRISMA-P items were fully reported). We also assessed adherence to each PRISMA-P item across the protocols.

Results: Four (8%) of the PubMed-indexed protocols adhered completely and 45 (90%) adhered partially to PRISMA-P but with considerable variation. None (0%) of the PROSPERO-uploaded protocols adhered completely and only 6 (12%) adhered partially to PRISMA-P. For both types of protocols, aspects related to the role of the sponsor, procedures for doing qualitative data synthesis if quantitative synthesis is not appropriate, and methods for assessing publication or outcome reporting biases and confidence in cumulative evidence were often not reported.

Conclusion: Adherence to the PRISMA-P reporting guideline was somewhat inadequate in PubMed-indexed protocols and clearly inadequate in PROSPERO-uploaded protocols. Authors of systematic review protocols who decide to report according to PRISMA-P should carefully check all items included in the guideline, and journal editors and peer reviewers should consider PRISMA-P adherence when reviewing protocols for potential publication.