Unpublished clinical trials of common rheumatic diseases

Randomized controlled trials (RCTs) provide high-quality evidence for treatment efficacy, but many RCTs remain unpublished. The objective of this study was to describe the proportion of unpublished RCTs in five rheumatic diseases and to identify factors associated with publication.

Registered RCTs for five rheumatic diseases (SLE, vasculitis, spondyloarthritis, SS and PsA) with over 30 months since study completion were identified using ClinicalTrials.gov. Index publications were identified by NCT ID numbers and structured text searches of publication databases. The results of unpublished studies were identified in abstracts and press releases; reasons for non-publication were assessed by surveying corresponding authors.

Out of 203 studies that met eligibility criteria, 17.2% remained unpublished, representing data from 4281 trial participants. Higher proportions of published trials were phase 3 RCTs (57.1% vs 28.6% unpublished, P < 0.05) or had a positive primary outcome measure (64.9% vs 25.7% unpublished, P < 0.001). In a multivariable Cox proportional hazards model, a positive outcome was independently associated with publication (hazard ratio 1.55; 95% CI: 1.09, 2.22). Corresponding authors of 10 unpublished trials cited ongoing preparation of the manuscript (50.0%), sponsor/funder issues (40.0%) and unimportant/negative result (20.0%) as reasons for lack of publication.

Nearly one in five RCTs in rheumatology remain unpublished 2 years after trial completion, and publication is associated with positive primary outcome measures. Efforts to encourage universal publication of rheumatology RCTs and reanalysis of previously unpublished trials should be undertaken.