Measurement of percent free prostate specific antigen: Increased discrimination between prostate cancer and Benign Prostatic Hyperplasia.

In this retrospective analysis we investigated whether the free-to-total PSA ratio (f-PSA/t-PSA ratio; i.e. percent free PSA) offers a better discriminant for the detection of cancer of the prostate (CaP) in patients with serum PSA levels between 4 and 10 ng/mL. The percent free PSA was determined in sera of 26 patients with histologically proven Benign Prostatic Hyperplasia (BPH) and 24 patients with clinically localized Cap Patients with urolithiasis (N=30) served as a control group. Serum levels of free PSA and total PSA were determined employing a chemiluminescent enzyme immunoassay. Patients with Cap demonstrated a lower percent free PSA (median: 9.2) than patients with BPH (median: 17.9; p<0.001) and those with urolithiasis (median: 18.2; p<0.001). We conclude that determination of percent free PSA enhances the discrimination between BPH and CaP and may reduce the number of unnecessary biopsies in patients with a PSA in the diagnostic gray zone. Confirmation of our preliminary retrospective results in a prospective study is warranted.