In patients with PSA values between 4.9 and 5.7 μg/L, in which the PSA rule-out power for advanced PCa is decreasing, a second level test, such as the 4-kallikrein panel score (4Kscore), may aid in the identification of advanced cancer risk, assuring a PPV > 95% [21]. The gene discussed is KLK3; the disease is cancer.