The detection rate of prostate cancer in Japanese subjects with PSA levels ≤ 2.0, 2.1–4.0, 4.0–10.0, and ≥ 10.0 ng/mL is 4.6%, 8.6%, 15.8%, and 59.5%, respectively; however, the specificity is not high [10]. Here, KLK3 is linked to prostate cancer.