Cookies on this website

We use cookies to ensure that we give you the best experience on our website. If you click 'Accept all cookies' we'll assume that you are happy to receive all cookies and you won't see this message again. If you click 'Reject all non-essential cookies' only necessary cookies providing core functionality such as security, network management, and accessibility will be enabled. Click 'Find out more' for information on how to change your cookie settings.

© 2014 Ramagopalan S et al. An important principle in the good conduct of clinical trials is that a summary of the trial protocol, with a pre-defined primary outcome, should be freely available before the study commences. The clinical trials registry provides one method of doing this, and once the trial is registered, any changes made to the primary outcome are documented. The objectives of this study were: to assess the proportion of registered trials on that had the primary outcome changed; to assess when the primary outcome was changed in relation to the listed study start and end dates and to assess whether the primary outcome change had any relation to the study sponsor. Methods: A cross-sectional analysis of all interventional clinical trials registered on as of 25 October 2012 was performed. The main outcome was any change made to the initially listed primary outcome and the time of the change in relation to the trial start and end date. Findings: Our analysis showed that 28229 of 89204 (31.7%)registered studies had their primary outcome changed. Industry funding was associated with all primary outcome changes, odds ratio (OR)= 1.36, 95% confidence interval (CI)=1.31-1.41, p&<0.001; with primary outcome changes after study start date OR=1.37, 95% CI=1.32-1.42, p&<0.001; with primary outcome changes after primary completion date OR=1.84, 95% CI=1.75-1.94, p&<0.001 and with primary outcome changes after study completion date OR=1.82, 95% CI=1.73-1.91, p&<0.001. Conclusions A significant proportion of interventional trials registered on have their primary outcomes altered after the listed study start and completion dates. These changes are associated with funding source.

Original publication




Journal article



Publication Date