Trial registration, publication rate and characteristics in the research field of otology: A cross-sectional study

OBJECTIVES: To examine 1) the publication rate of registered otology trials in ClinicalTrials.gov, 2) the public availability of the results, 3) the study characteristics associated with publication, and 4) the time to publication after trial completion. BACKGROUND: Publication bias, the publication or non-publication of research findings, depending on the nature and direction of results, is accountable for wrong treatment decisions. The extent of publication bias in otology trials has not been evaluated. METHODS: All registered otology trials were extracted from ClinicalTrials.gov with completion date up to December 2015. A search strategy was used to identify corresponding publications up to June 2017, providing at least 18 months to publish the results after trial completion. Characteristics were obtained from ClinicalTrials.gov and corresponding publications. Regression models were used to examine study characteristics associated with publication or non-publication. RESULTS: From the 419 trials identified on ClinicalTrials.gov, 225 (53.7%) corresponding publications were found in PubMed. Among these, 109 (48.4%) publications were cited on ClinicalTrials.gov and 124 (55.1%) articles reported the National Clinical Trial registry number. For 36 (8.6%) trials, results were only reported in ClinicalTrials.gov. Trials with a biological intervention were more likely to be published than studies involving drugs (odds ratio (OR) 10.41, 95% confidence interval (CI) 1.26–86.22, P = 0.030). Trials funded by industry were less likely to be published (OR 0.46, CI 0.25–0.84, P = 0.011). The median trial duration was 20 months (interquartile range (IQR) 26 months), and median time from trial completion to publication was 24 months (IQR 22 months). CONCLUSION: In 37.7% of the registered otology trials the results remained unpublished, even several years after trial completion. With little citations on ClinicalTrials.gov and low reporting of the Clinical Trial registry number, the accessibility is limited. Our findings show that there is room for improvement in accuracy of trial registration and publication of results, in order to diminish publication bias in otology studies.