Availability of study protocols for randomized trials published in high-impact medical journals: A cross-sectional analysis

Abstract

Background: To improve reporting transparency and research integrity, some journals have begun publishing study protocols and statistical analysis plans alongside trial publications. We sought to assess the overall availability and characteristics of protocols and statistical analysis plans of randomized clinical trials published in the top five (by impact factor) general medicine journals.

Methods: All randomized clinical trials published in Annals of Internal Medicine, BMJ, JAMA, Lancet, and NEJM in 2016 were identified. For each randomized clinical trial, we searched for protocols and statistical analysis plans on journal websites (including supplementary material) and in the article, for example, a referenced publication or link to trial or institutional website. Characteristics of randomized clinical trials were extracted from the publication and clinical trial registry. A detailed assessment of protocols and statistical analysis plans was conducted in a 20% random sample of randomized clinical trials.

Results: Protocols were available for 299 (82%) trials, ranging from 50% in BMJ to >95% in NEJM and JAMA. Statistical analysis plans were available for 182 (50%) trials and varied from <10% for Annals of Internal Medicine, BMJ, and Lancet to 92% for NEJM. Of the 76 randomized clinical trials in the 20% random sample, 63 (83%) had a protocol but less than half (31; 44%) included an a priori (dated prior to patient enrollment) version of the protocol. Statistical analysis plans were available for 35 (46%) trials, and only 5 (7%) included an a priori version.

Conclusion: Protocols and statistical analysis plans are publicly available for the majority of trials. However, the a priori versions of these documents are only available for a minority of trials. More attention must be paid to ensuring the public availability of a priori versions.

Keywords: Clinical trials; protocols; statistical analysis plan.