Selective Outcome Reporting among Randomized Controlled Trials Published in Leading Dental Journals: A Research-on-Research Study

Objectives: To study the prevalence and manifestation of selective outcome reporting (SOR) among randomized controlled trials (RCTs) published in leading dental journals, and to explore the association between SOR and potentially related factors.

Methods: We hand-searched RCTs published in the leading dental journals between 2018 and 2023. RCTs with registrations and defined primary outcomes were included, and their relevant characteristics were extracted for analysis. Discrepancies between publication and corresponding registration were compared regarding primary outcome and other study characteristics. The generalized estimating equation model was applied to identify factors associated with SOR.

Results: Two hundred and seventy trials were included. SOR was identified in 51.5% (n = 139) of the included RCTs with the discrepancy in the assessment timing of the primary outcome as the most common manifestation (n = 86, 31.9%). Substantial discrepancies were observed regarding sample size (n = 148, 54.8%) and source of funding (n = 105, 38.9%). Sample size [odds ratio (OR) 0.61, 95% confidence interval (CI) 0.40 to 0.92], timing of registration (OR 2.10, 95% CI 1.03 to 4.31), and discrepancy in follow-up length (OR 32.01, 95% CI 11.80 to 86.83) were identified as statistically significant factors associated with SOR.

Conclusions: SOR was prevalent among RCTs in leading dental journals. Researchers and other stakeholders should be aware of this reporting issue and make joint efforts to improve the outcome reporting quality.

Clinical significance: The findings of this research-on-research study indicate a substantial presence of SOR in the field of dentistry. Such bias can potentially mislead readers and distort the pooled effect estimates in evidence synthesis, ultimately influencing clinical decision-making.