Background: Clinical trial registries have been created to reduce reporting bias. Study registration enables the examination of discrepancies between the original study design and the final results reported in the literature. The main objective of the current investigation is to compare the original clinical trial registrations and the corresponding published results in high-impact anesthesiology journals. Specifically, we examined the rates of major discrepancies (i.e., involving primary outcome, sample size calculation, or study intervention).
Methods: The 5 highest-impact factor anesthesiology journals (Anaesthesia, Anesthesia & Analgesia, Anesthesiology, British Journal of Anaesthesia, and Regional Anesthesia and Pain Medicine) were screened for randomized controlled trials published in 2013. A major discrepancy was defined as a difference in the content of the manuscript compared with the original entry in a clinical trial registry for at least one of the 3 areas: primary outcome, target sample size, and study intervention. The type of primary outcome discrepancy was further classified as adding/omitting measures or outcomes, downgrading/upgrading from primary to secondary outcomes, or changing the definition of the outcomes measured.
Results: Two hundred one articles were included in the final analysis. One hundred thirty of 201 (64%; 95% confidence interval [CI], 57%-71%) published clinical trials were not prospectively registered as recommended by the International Committee of Medical Journal Editors. Registration rates were significantly lower between studies performed in the United States, 15 of 40 (37%), compared with studies not performed in the United States, 92 of 161 (57%), P = 0.03. Fifty-two of 107 (48%; 95% CI, 39%-58%) registered trials had a major discrepancy when the published manuscript was compared with the clinical trial registration. Thirty-one of the 46 (67%; 95% CI, 51%-80%) primary outcome discrepancies had changes in the outcome with characteristics of reporting bias.
Conclusions: We detected a high rate of major discrepancies between the published results and the original registered protocols for clinical trial manuscripts in high-impact anesthesiology journals. Future action to reduce the negative impact of reporting bias in the anesthesiology field is warranted.