KLK3 and neoplasm: To note, the four-gene model also performs well in the diagnostic PSA gray-zone (PSA 3–10 ng/ml) yielding a SN of 79 % for discriminating between tumor urines from patients with PSA serum values between 3 and 10 ng/ml and control urines, with a SP of 59 % (PPV = 72 %; NPP = 68 %; ER = 29 %; p < 0.001) (Fig. 1b).