In model A, the estimated standard deviation of between-practice variation was 0.66 (95% CI = 0.57 to 0.77), which translates to a 95% mid-range OR of 13.4, that is, an over 13-fold variation in the odds of detecting prostate cancer through asymptomatic PSA testing between practices with the highest and lowest rates (ignoring the 5% of extreme practices). This evidence concerns the gene KLK3 and prostate carcinoma.