Indicators of questionable research practices were identified in 163,129 randomized controlled trials

OBJECTIVE: To explore indicators of the following questionable research practices (QRPs) in randomized controlled trials (RCTs): (1) risk of bias in four domains (random sequence generation, allocation concealment, blinding of participants and personnel, and blinding of outcome assessment); (2) modifications in primary outcomes that were registered in trial registration records (proxy for selective reporting bias); (3) ratio of the achieved to planned sample sizes; and (4) statistical discrepancy.

STUDY DESIGN AND SETTING: Full-texts of all human RCTs published in PubMed in 1996-2017 were automatically identified, and information was collected automatically. Potential indicators of QRPs included author-specific, publication-specific, and journal-specific characteristics. Beta, logistic, and linear regression models were used to identify associations between these potential indicators and QRPs.

RESULTS: We included 163,129 RCT publications. The median probability of bias assessed using RobotReviewer software ranged between 43% and 63% for the four risk of bias domains. A more recent publication year, trial registration, mentioning of CONSORT-checklist, and a higher journal impact factor were consistently associated with a lower risk of QRPs.

CONCLUSION: This comprehensive analysis provides insight into indicators of QRPs. Researchers should be aware that certain characteristics of the author team and publication are associated with a higher risk of QRPs.