In the UK Cluster randomised triAl of PSA testing for prostate cancer (CAP Trial) of 419 582 men, using a single PSA test, followed by a standard transrectal biopsy if the PSA was between 3 and 19.9 ng/mL, there was no difference in prostate cancer mortality in the PSA screened and control arms.5 Here, KLK3 is linked to prostate carcinoma.