Evaluating the evidence: statistical methods in randomized controlled trials in the urological literature

Abstract

Purpose: Randomized controlled trials potentially provide the highest level of evidence to inform clinical decision making. Appropriate use of statistical methods is a critical aspect of all clinical research, including randomized controlled trials. We report the first formal evaluation to our knowledge of the statistical methods of randomized controlled trials published in the urological literature in 1996 and 2004.

Materials and methods: All human subjects randomized controlled trials published in 4 leading urology journals in 1996 and 2004 were identified for formal review. A standardized evaluation form was developed based on the Consolidated Standards of Reporting Trials statement. Each article was evaluated by 2 independent reviewers with formal training in research design and biostatistics who were blinded to study authors and institution. Discrepancies were settled by consensus.

Results: A total of 152 randomized controlled trials were reviewed (65 in 1996, 87 in 2004). The median sample size (IQR) per arm of parallel design randomized controlled trials published in 1996 and 2004 was 36 (11, 96) and 50 (26, 134) study subjects, respectively (p = 0.157). Sample size justifications were provided by 19% of studies in 1996 and 47% of studies in 2004 (p = 0.001). Of randomized controlled trials 16 (25%) vs 32 (37%) identified a single primary outcome variable (p = 0.110). Effect size estimates for primary or secondary outcome variables were provided by 5% vs 13% (p = 0.090) and the precision of the effect was detailed by 5% vs 10% of randomized controlled trials (p = 0.195).

Conclusions: This formal review suggests that statistical analysis in urological randomized controlled trials has improved. However, considerable deficiencies remain. Ongoing education in applied statistics may further improve urological randomized controlled trial reporting.