Statistical significant results in regional anesthesia randomized controlled trials: Investigating prevalence, associated factors and implications – A systematic review

Background: Randomized controlled trials (RCTs) are the gold standard for evaluating medical interventions, including regional anesthesia (RA). However, growing evidence suggests that not statistically significant studies may be unreported, skewing the existing core of evidence. This study evaluates the prevalence of significant results in RA RCTs and explores possibly associated factors. Methods: We analyzed RCTs from 136 journals in the "Anesthesia and Pain Medicine" category (Scopus CiteScore). Of 4524 articles retrieved, 1079 RA RCTs were included following manual review. Studies were classified as "statistically significant" ot "not statistically significant" based on primary outcome significance (p < 0.05). Logistic regression identified factors associated with statistical significance, with model performance metrics evaluated. Results: Among the 1079 RCTs, 241 (22.3%) reported not statistically significant results. Factors associated with statistically significant findings included studies focused on RA techniques (OR 2.28; 95% CI: 1.12-4.63), those investigating pediatric populations (OR 3.39; 95% CI: 1.19-9.66) and studies not receiving fundings (OR 0.67; 95% CI 0.46-0.98). Monocentric studies (95.8%) and non-active comparators (40.4%) were common, potentially influencing outcomes. Performance metrics (AUC: 0.690) indicated robust model reliability. Conclusion: A high proportion of RA RCTs report statistically significant results, and these outcomes are associated with study design and comparator choice.