Reporting of a publicly accessible protocol and its association with positive study findings in cardiovascular trials (from the epidemiological study of randomized trials [ESORT])

Selective outcome reporting is common among published randomized trials and is often associated with the reporting of positive study findings. We investigated whether publication of study protocols in publicly accessible formats is associated with the reporting of positive findings. An extended version of the Cochrane highly sensitive search strategy was used to identify reports of randomized trials on cardiovascular disease that were published in December 2012 and indexed in PubMed by November 2013. Study characteristics and methodologic characteristics were extracted in duplicate. The Fisher's exact test and multivariable logistic regression were used to compare characteristics between trials that reported a publicly accessible protocol and those that did not. One hundred ninety-one reports of cardiovascular randomized trials were identified, 23 (12%) of which reported an accessible protocol. Trials reporting an accessible protocol were significantly larger and more likely to report strong trial methods, including reporting a power calculation, attrition, and the use of an intention-to-treat analysis. Despite greater statistical power, trials reporting an accessible protocol were less likely to report positive findings after controlling for known confounders (odds ratio 0.35, 95% confidence interval 0.13 to 0.94). Reporting of an accessible protocol is associated with a reduced likelihood of reporting positive findings. Further investigation is needed to determine if this association is causal.