Inclusion of harm outcomes in core outcome sets requires careful consideration.

Objectives: The objective of this study was to determine the proportion of all published core outcome set (COS) studies that include an adverse event or harm outcome, to determine the proportion of individual vs pooled harms, and to investigate characteristics that influence their inclusion.

Methods: We examined the extent to which a sample of 100 published COS studies (from January 2021 to January 2023) include both pooled and individual harms in the final COS. One investigator extracted the information from the COS studies, which was cross-checked against previous COS investigational research, and where possible verified with COS authors or a pharmacologist. Using Qualtrics™, we conducted a personalized online survey of developers of the 100 COS to ask them about the importance, their experiences, and methodological approaches for dealing with harms within their COS development studies.

Results: One hundred COS were identified from 91 separate COS studies, the majority of which considered most of the minimum standards for development. Two-thirds (65%) of the COS included at least 1 harm outcome. In total, 1104 core outcomes were identified across the 100 COS, of which 184 (17%) were harm outcomes (154 individual vs 56 pooled). Individual harms were more likely to be included in a final COS if they were developed for single treatment interventions (50%) compared to those being developed for multitreatment modalities (39%). Some COS developers adopted outcome frameworks as part of their COS development process to facilitate the inclusion of harm outcomes in their final COS. A third (33%) of respondents felt that harm outcomes should be included in all COS but over half (56%) thought this would be dependent on some aspect of the scope of the COS and improved methodology and awareness of how to deal with harm outcomes in the COS development process.

Conclusion: Harm outcomes are already included in many COS either as individual or pooled harms. It is evident that there are some challenges with regards to both the methodology and necessity to include harms within a COS (pooled or individual. COS developers should carefully consider the need to include important harms outcomes in relation to the scope of the COS that they are developing.