The 4Kscore test combines information from four kallikrein markers in the blood [total PSA, free PSA, intact PSA, and human kallikrein-related peptidase 2 (hK2), a serine protease coded for by a kallikrein gene and expressed primarily through the prostate epithelium (4, 5)], and age to provide patients with a predicted risk between 0% and 100% of them having a high-grade tumor (Gleason score ≥7) detected on a prostate biopsy (6). The gene discussed is KLK4; the disease is neoplasm.