Clinical trials often go unregistered or unpublished and have differences in the reporting of primary outcomes, according to a study published in JAMA.

Registration of clinical trials is meant to identify and deter selective reporting of outcomes based on results, but it is unknown whether registered outcomes accurately represent trial protocol or if registration improves the reporting of primary outcomes in published trials. Led by An-Wen Chan, MD, DPhil, of the Women's College Research Institute at the University of Toronto, researchers analyzed adherence to trial registration and its correlation to publication.

The study included data of primary outcomes of 113 clinical trial protocols approved in 2007. Results showed 61 percent of the trials were registered within one month of the start date and 57 percent were published. Primary outcomes were not outlined in 20 percent of trials. Differences between protocol and publication occurred in 55 percent of unregistered trials and only 6 percent of registered trials. Prospective registration was correlated with publication with 68 percent of registered trials, and 39 percent of unregistered trails were published. Registered trails were also more likely to be published with the same primary outcomes outlined in the protocol, at 64 percent, than unregistered trials, at 25 percent.

"Journal editors, regulators, research ethics committees, funders, and sponsors should implement policies mandating prospective registration for all clinical trials,” concluded Chan and colleagues. “Only with accessible, complete information can interventions be adequately evaluated for patient care.”