Evidence of publication bias in multiple sclerosis clinical trials: a comparative analysis of published and unpublished studies registered in ClinicalTrials.gov

Complete and timely publication of clinical trials ensures that patients and the medical community are fully informed when making treatment decisions. The aim of this study is to assess the publication of phase III and IV clinical trials on multiple sclerosis (MS) drugs that have been carried out between 2010 and 2019 and to identify the factors associated with their publication in peer-reviewed journals.An advanced search in ClinicalTrials.gov was performed and consecutive searches in PubMed, EMBASE and Google Scholar were conducted looking for the associated publications of all completed trials. Study design characteristics, results and other relevant information were extracted. Data was analysed following a case-control design. Clinical trials with associated publications in peer-reviewed journals were the cases and unpublished trials were the controls. A multivariate logistic regression analysis was performed to identify factors associated with trial publication.One hundred and fifty clinical trials were included in the analysis. Ninety-six of them (64.0%) were published in peer-reviewed journals. In the multivariate analysis, factors associated with trial publication were a favourable primary outcome (OR 12.49, 95% CI 1.28 to 122.29) and reaching the originally estimated sample size (OR 41.97, 95% CI 1.96 to 900.48), while those associated with a lower odds of publication were having 20% or more patients lost to follow-up (OR 0.03, 95% CI 0.01 to 0.52) and evaluating drugs intended to improve treatment tolerability (OR 0.01, 95% CI 0.00 to 0.74).Phase III and IV clinical trials on MS drugs are prone to under-reporting and publication bias. Efforts must be made to promote a complete and accurate dissemination of data in MS clinical research.