KLK3 and prostate cancer: Much debate exists over the usefulness of prostate specific antigen (PSA) as a biomarker for the detection of prostate cancer, however the data suggest that it can provide useful information in assisting in the diagnosis of this disease with PSA concentrations 4–10 ng/mL having a 25% positive predictive value, to greater than 80% in men with a PSA >20 ng/mL [15].