Abstract
BACKGROUND: Randomized controlled trials (RCTs) are designed to achieve balanced distribution of baseline characteristics across study arms through random allocation, rendering null-hypothesis significance testing on these characteristics unnecessary and potentially misleading. Despite longstanding guidance discouraging this practice, its prevalence and patterns within anesthesiology and pain medicine literature remain unclear. METHODS: The authors conducted a meta-research study of parallel-group RCTs published from 1996 to 2025 across 101 journals indexed under the "Anesthesiology and Pain Medicine" category in Scopus (Elsevier, The Netherlands). Data extraction included study characteristics, reporting of baseline testing, number of variables tested, and statistical significance. Multivariable logistic regression was used to identify factors associated with baseline testing, and a binomial test assessed whether the observed rate of significant findings exceeded the expected false-positive rate under the null hypothesis. RESULTS: Of 2,453 eligible RCTs, 1,186 (48.3%) reported statistical testing of baseline characteristics. Among studies performing such testing, 228 (19.2%) reported at least one statistically significant difference, and 58 (25.4%) discussed it as a study limitation. A total of 11,516 variables were tested, with 424 (3.7%) reported as statistically significant-below the 5% expected by chance ( P < 0.001). Larger author teams were associated with lower odds of baseline testing (odds ratio, 0.95; 95% CI, 0.93 to 0.97), while a higher number of variables tested increased the odds of finding at least one significant difference (odds ratio, 1.10; 95% CI, 1.07 to 1.12). CONCLUSIONS: Despite methodologic guidance and Consolidated Standards of Reporting Trials (CONSORT) recommendations, statistical testing of baseline characteristics remains common in anesthesiology RCTs and has not declined over time. This practice likely reflects persistent misunderstanding of randomization and may lead to misinterpretation of study validity. Education and stronger editorial policies are needed to align reporting behavior with best practices and improve trial transparency.