['We tested the hypothesis that serum isoform [-2]proPSA derivatives %p2PSA and Prostate Health Index are accurate predictors of prostate cancer in men scheduled for repeat biopsy.', 'The study was an observational prospective evaluation of a clinical cohort of men with 1 or 2 previous negative prostate biopsies, with persistent suspicion of prostate cancer. They were enrolled in the study to determine the diagnostic accuracy of %p2PSA using the formula, (p2PSA pg/ml)/(free prostate specific antigen ng/ml × 1,000)]× 100, and Beckman-Coulter Prostate Health Index using the formula, (p2PSA/free prostate specific antigen) × √total prostate specific antigen), and to compare it with the accuracy of established prostate cancer serum tests (total prostate specific antigen, free prostate specific antigen and percent free prostate specific antigen). Multivariable logistic regression models were complemented by predictive accuracy analysis and decision curve analysis.', 'Prostate cancer was found in 71 of 222 (31.9%) subjects. %p2PSA and Prostate Health Index were the most accurate predictors of disease. %p2PSA significantly outperformed total prostate specific antigen, free prostate specific antigen, percent free prostate specific antigen and p2PSA in the prediction of prostate cancer (p ≤0.01), but not Prostate Health Index (p = 0.094). Prostate Health Index significantly outperformed total prostate specific antigen and p2PSA (p ≤0.001) but not free prostate specific antigen (p = 0.109) and free/total prostate specific antigen (p = 0.136). In multivariable logistic regression models %p2PSA and Prostate Health Index achieved independent predictor status, and significantly increased the accuracy of multivariable models including prostate specific antigen and prostate volume with or without percent free prostate specific antigen and prostate specific antigen density by 8% to 11% (p ≤0.034). At a %p2PSA cutoff of 1.23, 153 (68.9%) biopsies could have been avoided, missing prostate cancer in 6 patients. At a Prostate Health Index cutoff of 28.8, 116 (52.25%) biopsies could have been avoided, missing prostate cancer in 6 patients.'] Are serum index test % [ -2 ] proPSA and Prostate Health Index more accurate than prostate specific antigen and % fPSA in predicting a positive repeat prostate biopsy?