Objectives Randomized controlled trials (RCTs) provide high-quality evidence for treatment efficacy, but many RCTs remain unpublished. The objective of this study was to describe the proportion of unpublished RCTs in 5 rheumatic diseases and to identify factors associated with publication. Methods Registered RCTs for 5 rheumatic diseases (systemic lupus erythematosus, vasculitis, spondyloarthritis, Sjögren’s syndrome, and psoriatic arthritis) 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 The results of unpublished studies were identified in abstracts and press releases; reasons for non-publication were assessed by surveying corresponding authors. Results Out of 203 studies that met eligibility criteria, 17.2% remained unpublished, representing data from 4,281 trial participants. Higher proportions of published trials were phase 3 RCTs (57.1% vs 28.6% unpublished, p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 0.05) or had a positive primary outcome measure (64.9% vs 25.7% unpublished, p 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 (HR 1.55, 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 Corresponding authors of 10 unpublished trials cited ongoing preparation of the manuscript (50.0%), sponsor/funder issues (40.0%), and unimportant/negative result (20.0%) as reasons for lack of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. Conclusions Nearly one in five RCTs in rheumatology remain unpublished two years after trial completion, and publication is associated with positive primary outcome measures. Efforts to encourage universal publication of rheumatology RCTs and reanalysis of previously unpublished trials should be undertaken.

Background Comparative efficacy randomized controlled trials (RCTs) compare two active interventions in a head‐to‐head design. They are useful for informing clinical practice guidelines, but the degree to which such trials inform clinical practice guidelines in rheumatology is unknown. Methods The American College of Rheumatology (ACR) and European Alliance of Associations for Rheumatology (EULAR) websites were searched from January 1, 2017, to June 12, 2021, for clinical practice guidelines. RCTs referenced by each guideline were identified, and information regarding design and outcomes were extracted. Clinical practice recommendations from each guideline were also analyzed. Results Fifteen ACR‐ and nine EULAR‐endorsed guidelines were included, which cited 609 RCTs and provided 481 recommendations. Referenced RCTs enrolled an average of 418 patients (SD 985), most commonly evaluated biologic/targeted synthetic disease‐modifying antirheumatic drugs (70.1%), and infrequently used a head‐to‐head design (28%). A minority of recommendations received a high level of evidence (LOE) by the Grades of Recommendation, Assessment, Development, and Evaluation (GRADE) methodology (2.9%) or an “A” grade by the Oxford Centre for Evidence based Medicine Standards (OCEBM) methodology (28.9%). LOE was higher for recommendations informed by RCTs (P < 0.001) or head‐to‐head RCTs (P = 0.008). Many recommendations received a strong recommendation despite low (8 [2.6%]) or very low (25 [8.3%]) LOE. Conclusion Less than one in six rheumatology guideline recommendations are informed by head‐to‐head RCTs. Recommendations that were informed by head‐to‐head RCTs were more likely to have a high LOE by both GRADE and OCEBM. Efforts to introduce more comparative efficacy RCTs should be undertaken.