Registration of clinical trials facilitates transparency in study conduct and reporting. Public reporting of serious adverse events (SAEs) in clinical trial registries allows independent review of harms associated with an intervention. Discrepancy between registry data and publications may indicate concealment of results, leading to reporting bias. No study has compared SAE reporting between trial registries and the primary publications included in network meta-analyses (NMAs). Potential reporting bias should be explored, as the validity of NMAs depends on the quality and accuracy of the published studies.
To determine if there is a difference in the frequency of overall SAEs reported in clinical trial registrations and their respective primary publications.
We conducted a retrospective review of the published randomized controlled trials (RCTs) included in two recent NMAs investigating cognitive enhancers for Alzheimer's disease and long-acting inhaled agents for chronic obstructive pulmonary disease. We included RCTs published in 2005 or later (English only), since the International Committee of Medical Journal Editors (ICMJE) mandated the registration of clinical trials for results to be eligible for publication in its member journals in 2005. Two reviewers independently abstracted study and SAE details from the included study publications and trial registrations.
Of the 203 RCTs included from the two NMAs, 136 (67.0%) were registered with a clinical trial registry (131 within ClinicalTrials.gov, five within another public registry) and 67 (33.0%) posted results in the registry. Of the publications with results posted in a clinical trial registry, 14 (20.9%) had inconsistent reporting of overall SAEs (publication vs registry); seven (10.4%) studies did not report SAEs in the publication, but did in the registry. We will also explore the impact of adding new SAE data from ClinialTrials.gov on the existing NMA results.
We identified inconsistent reporting of SAEs in RCTs from two NMAs. Findings highlight the importance of including trial registries as part of the grey literature search and verifying safety data within these registries before incorporating it into meta-analyses and NMAs.
Patients were indirectly involved with the original NMAs by selecting outcomes of interest.