KLK3 and prostate cancer: Based on the publications, the American National Comprehensive Cancer Network (NCCN) suggested considering PHI in men with PSA 2.5–10 ng/mL, especially if previous biopsy was negative.41 The second, the Four Kallikrein Assay (4Kscore) incorporates total PSA, free PSA, intact PSA, and human kallikrein-related peptidase 2 measurements to increase detection of significant prostate cancer.