Original Article
Over a third of systematic reviews did not fully report the adverse events outcome

Under a Creative Commons license
open access



To assess the risk for adverse events reporting bias in systematic reviews of healthcare interventions registered to PROSPERO.

Study Design and Setting

Retrospective cohort study. Systematic review protocols in PROSPERO were screened and included if they focused on a healthcare intervention and listed an adverse event as either a primary or secondary outcome. The included systematic reviews were assessed to determine the completeness of reporting for the adverse effect outcomes. Any discrepancies in reporting between protocol and review were recorded.


Of 1376 protocols for systematic reviews sifted only 524 (38%) listed adverse events outcomes. 186 protocols were published in 2017 and 2018 of which 146 were included in our analysis. Among the included systematic reviews, 65% (95/146) fully reported the adverse effect outcomes as intended by the protocol, 8% (12/146) entirely excluded the adverse effect outcome, and the remaining 27% (39/146) either partially reported or changed the adverse effect outcomes.


62% of reviews did not mention adverse events in their protocol and 35% of PROSPERO-registered systematic reviews had discrepant outcome reporting between the protocol and publication. The findings suggest a need for the encouraged use of harms reporting guidelines and further research into adverse events reporting bias.


Adverse events
Systematic reviews
Outcome reporting bias