Abstract
Background: Adverse events (AEs) in randomized clinical trials may be reported in multiple sources. Different methods for reporting adverse events across trials, or across sources for a single trial, may produce inconsistent and confusing information about the adverse events associated with interventions
Methods: We sought to compare the methods authors use to decide which AEs to include in a particular source (i.e., “selection criteria”) and to determine how selection criteria could impact the AEs reported.
We compared sources (e.g., journal articles, clinical study reports [CSRs]) of trials for two drug-indications: gabapentin for neuropathic pain and quetiapine for bipolar depression. We identified selection criteria and assessed how criteria affected AE reporting.
Results: We identified 21 gabapentin trials and 7 quetiapine trials. All CSRs (6 gabapentin, 2 quetiapine) reported all AEs without applying selection criteria; by comparison, no other source reported all AEs, and 15/68 (22%) gabapentin sources and 19/48 (40%) quetiapine sources reported using selection criteria. Selection criteria greatly affected the number of AEs that would be reported. For example, 67/316 (21%) AEs in one quetiapine trial met the criterion “occurring in ≥2% of participants in any treatment group,” while only 5/316 (2%) AEs met the criterion, “occurring in ≥10% of quetiapine-treated patients and twice as frequent in the quetiapine group as the placebo group.”
Conclusions: Selection criteria for reporting AEs vary across trials and across sources for individual trials. If investigators do not pre-specify selection criteria, they might “cherry-pick” AEs based on study results. Even if investigators pre-specify selection criteria, selective reporting of AEs will produce biased meta-analyses and clinical practice guidelines. Data about all AEs identified in clinical trials should be publicly available; however, sharing data will not solve all the problems we identified in this study.
Keywords: Harms, adverse events, clinical trials, reporting bias, selective outcome reporting, data sharing, trial registration