Pre-specification of endpoints is a fundamental principle when designing and reporting randomised trials. The registration of randomised trials in clinicaltrials.gov enables an evaluation of whether reported endpoints are pre-specified or have been changed.
Ramagopalan et al. performed a cross-sectional analysis of all interventional clinical trials registered on ClinicalTrials.gov as of 25 October 2012. The analysis showed that 28229 of 89204 (32%) registered studies had their primary outcome changed. The authors also found that industry funding was associated with a higher degree of endpoint changes of the primary outcome than public funding.
The authors conclude that a significant proportion of the trials registered at clinicaltrials.gov have their primary outcomes changed and that the changes are associated with the funding source.
- Ramagopalan S, Skingsley AP, Handunnetthi L, Klingel M, Magnus D, Pakpoor J, Goldacre B. Prevalence of primary outcome changes in clinical trials registered on ClinicalTrials.gov: a cross-sectional study. F1000Research 2014,3:77.