This recommendation is based on retrospective findings from the STHLM3 trial, in which 16.8% of patients with elevated PSA (3–10 ng/ml) on initial testing had a normal level of ≤3 ng/ml on repeat measurement, and on findings from the ProtecT trial, in which men with a ≥20% reduction in PSA on repeat testing had significantly lower risk of harbouring prostate cancer [2], [3]. This evidence concerns the gene KLK3 and prostate cancer.