Transparency of results reporting for depression treatment studies in ClinicalTrials.gov: a cross-sectional study

Posting of clinical trial results and other critical information from completed medicines trials on ClinicalTrials.gov

PURPOSE

Clinical trials transparency requires trial registration and the posting of results on a public register. US regulations also require the posting of protocols and statistical analysis plans (SAPs). For US Federal agency funded trials to be started on or after 21 January 2019, informed consent forms (ICFs) must also be posted. Posting these documents is not mandatory in other countries. We aimed to assess compliance with US regulations of trials conducted in the US or in other countries with respect to ICFs, protocols, SAPs, and results.

METHODS

This cross-sectional analysis (27 April 2023) comprised completed medicines trials to be started on or after 21 January 2019 registered on ClinicalTrials.gov. Trial data were registered by funder type (i.e., 'US federal agencies', industry, and 'all others') and development phase.

RESULTS

Of 5,584 trials, 40% were conducted solely in the US. 47% and 12% of US and non-US trials had posted results. Some 40% of US trials had posted protocols and SAPs as did 9% of trials conducted in other countries. Only 10% (US) and 2% (other countries) of trials had posted ICFs. When the margin of the last 2 and 12 months after primary completion date were considered in the analysis, ICF posting rate did not change, but posting results increased to 64% for US trials. 'US Federal agencies' funded trials were significantly more likely to post ICFs than industry [OR 23.9 (12.5-45.7; <.001)] or 'all others' [OR 3.16 (1.79-5.56; <.001)].

CONCLUSION

Future interventions should be considered to encourage timely posting of trial results and information.

Depression trial results: A cross-sectional study of ClinicalTrials.gov

Published clinical trials represent a subsample of the objective information needed to appraise treatments for depression. We characterize the extent of selective and delayed reporting in a systematic review (PROSPERO #CRD42020173606) of depression trial results registered on ClinicalTrials.gov. Inclusion criteria were studies registered on ClinicalTrials.gov with depression as the condition, had enrolled ages 18 and over, were completed between January 1, 2008 and May 1, 2019, and had posted results by February 1, 2022. Cox regression analyses of time to result posting from registration and from study completion included enrollment as a covariate. Among 442 protocols, median result posting occurred over two years after study completion and five years after registration. Among protocols with incomplete results, effect sizes (d or W) were calculated for 134 protocols. Median effect sizes for protocols with incomplete results were small (0.16, 95% CI 0.08, 0.21). For 28% of protocols, observed effects were contrary to the expected direction. Between-group effect size calculations were based on post-treatment data as pre-treatment data were inconsistently provided. Although drug and device trials in the U.S. are required to register on ClinicalTrials.gov, compliance is imperfect, and submissions are not peer reviewed. For depression treatment trials, long intervals between study completion and posting of results are common. Further, investigators often fail to report the results of statistical tests. Failure to post trial results in a timely manner and omission of statistical test reporting may lead to overestimates of treatment effects in systematic literature reviews.

Registration of health and medical research

Registration of health and medical research is an effective way of improving the transparency and credibility of evidence. Registration involves pre-specifying the research objectives, design, methods and analytic plan on a publicly accessible repository before conducting the study. Registration can reduce bias and improve the transparency and credibility of research findings. Registration is mandated for clinical trials, but it is also relevant to systematic reviews, observational and preclinical experimental research. This paper describes how researchers can register their research and outlines possible barriers and challenges in doing so. Widespread adoption of research registration can reduce research waste and improve evidence-informed clinical and policy decision making.