KLK3 and prostate cancer: Several studies have examined the rates of PSA testing in British men;17–21,30 however, these comprise study cohorts smaller than those in the study presented here,20 have focused purely on single geographical regions,17 or have limited time frames.18,19,21,30 Other studies have identified similar associations between PSA testing and age, ethnicity, level of deprivation, and geographical region,19,20,30 but none has examined as extensive a panel of covariates as the study presented here, or comprehensively assessed the associations with opportunistic prostate cancer screening.