To prospectively evaluate the performance of a prespecified statistical model based on four kallikrein markers in blood (total prostate-specific antigen [PSA], free PSA, intact PSA, and human kallikrein-related peptidase 2[hK2]), commercially available as the 4Kscore, in predicting Gleason grade group (GG) ≥2 prostate cancer at biopsy in an international multi-center study at three academic medical centers, and whether microseminoprotein-β (MSP) adds predictive value.