It has been evaluated in two large, randomised studies: The Prostate, Lung, Colorectal and Ovary (PLCO) study2 and the European Randomised Study of Screening for Prostate Cancer (ERSPC).3 Criticisms of PSA-screening include a high false-positive rate, over-diagnosis, complications associated with prostate biopsies and overtreatment of low-grade disease, but the ERSPC showed that after 22 years, mortality was approximately 30 percentage points higher in the control group compared with men who were offered screening through biennial PSA testing.3 Here, KLK3 is linked to prostate cancer.