Since non-malignant conditions such as prostatic inflammations and benign prostate hyperplasia might increase PSA levels, there is a great quest for an efficient second test, the so-called reflex test, which is able to increase the CDR of csPCa in patients with a PSA within the grey zone (3–10 ng/mL), while reducing the number of negative biopsy results and overdiagnosis of indolent PCa. The gene discussed is KLK3; the disease is benign prostatic hyperplasia.