Introduction: Registering study protocols in a trial registry is important for methodologic transparency and reducing selective reporting bias. The objective of this investigation was to determine whether published studies of intimate partner violence (IPV) that had been registered matched the registration record on key study design elements.
Methods: We systematically searched three trial registries to identify registered IPV studies and the published literature for the associated publication. Two authors independently determined for each study whether key study elements in the registry matched those in the published paper.
Results: We included 66 studies published between 2006 and 2017. Nearly half (29/66, 44%) were registered after study completion. Many (26/66, 39%) had discrepancies regarding the primary outcome, and nearly two-thirds (42/66, 64%) had discrepancies in secondary outcomes. Discrepancies in study design were less frequent (13/66, 20%). However, large changes in sample size (26/66, 39%) and discrepancies in funding source (28/66, 42%) were frequently observed.
Conclusions: Trial registries are important tools for research transparency and identifying and preventing outcome switching and selective outcome reporting bias. Published IPV studies often differ from their records in trial registries. Researchers should pay close attention to the accuracy of trial registry records.
Keywords: Trial registration; bias; intimate partner violence; methodology; selective outcome reporting.