KLK4 and Familial prostate cancer: Previously, a prespecified statistical model based on measurements of four-kallikrein markers (free PSA, intact PSA, total PSA, and kallikrein-related peptidase 2 (hK2)) measured in blood and combined with age and DRE findings, commercially available as the 4Kscore has been demonstrated to accurately predict the presence of Grade group 2 or higher prostate cancer in patients undergoing TRUS biopsy6–9.