Role of editorial and peer review processes in publication bias: analysis of drug trials submitted to eight medical journals.

BACKGROUND: Publication bias is generally ascribed to authors and sponsors failing to submit studies with negative results, but may also occur after submission. We evaluated whether submitted manuscripts on randomized controlled trials (RCTs) with drugs are more likely to be accepted if they report positive results.

METHODS: Manuscripts submitted from January 2010 through April 2012 to one general medical journal (BMJ) and seven specialty journals (Annals of the Rheumatic Diseases, British Journal of Ophthalmology, Gut, Heart, Thorax, Diabetologia, and Journal of Hepatology) were included, if at least one study arm assessed the efficacy or safety of a drug and a statistical test was used to evaluate treatment effects. Publication status was retrospectively retrieved from submission systems or provided by journals. Sponsorship and trial results were extracted from manuscripts and classified according to predefined criteria. Main outcome measure was acceptance for publication.

RESULTS: Of 15,972 manuscripts submitted, 472 (3.0%) were drug RCTs, of which 98 (20.8%) were published. Among submitted drug RCTs, 287 (60.8%) had positive and 185 (39.2%) negative results. Of these, 60 (20.9%) and 38 (20.5%), respectively, were published. Manuscripts on non-industry trials (n = 213) reported positive results in 138 (64.8%) manuscripts, compared to 71 (47.7%) on industry-supported trials (n = 149), and 78 (70.9%) on industry-sponsored trials (n = 110). Twenty-seven (12.7%) non-industry trials were published, compared to 27 (18.1%) industry-supported and 44 (40.0%) industry-sponsored trials. After adjustment for other trial characteristics, manuscripts reporting positive results were not more likely to be published (OR, 1.00; 95% CI, 0.61 to 1.66). Submission to specialty journals, sample size, multicentre status, journal impact factor, and corresponding authors from Europe or US were significantly associated with publication.

CONCLUSIONS: For the selected journals, there was no tendency to preferably publish manuscripts on drug RCTs that reported positive results, suggesting that publication bias may occur mainly prior to submission.