A comparison of six commercial assays for total and free prostate specific antigen (PSA): the predictive value of the ratio of free to total PSA

Abstract

Although all six assays were equimolar, there were differences in calibration, particularly for fPSA. The ability of f/tPSA to discriminate between benign and malignant prostatic disease depended on the assay used. The f/tPSA is not valid when the tPSA and fPSA assays are obtained from different manufacturers.