Comparisons of the Various Combinations of Free, Complexed, and Total Prostate–Specific Antigen for the Detection of Prostate Cancer

Abstract

Objectives: We compared the ability of three prostate–specific antigen (PSA) ratios – free–to– total PSA ratio (fPSA/tPSA), free–to–complexed PSA ratio (fPSA/cPSA), and complexed–to–total PSA ratio (cPSA/tPSA) – to distinguish prostate cancer from benign prostatic hyperplasia (BPH).Methods: We tested 258 consecutive patients who underwent transrectal ultrasound–guided prostate needle biopsy because of an abnormal digital rectal examination or a Tandem–R PSA of >4.1 ng/ml. Free PSA (fPSA) and total PSA (tPSA) were measured by Tandem–R assay. α₁–Antichymotrypsin–complexed PSA (cPSA) was measured by Markit–M PSA–ACT assay.Results: Of the 258 patients, 204 had BPH, and 54 had prostate cancer. The specificity at 96% sensitivity for fPSA/tPSA, fPSA/cPSA, and cPSA/tPSA was 23, 25, and 33%, respectively. Of 162 patients with tPSA between 4.1 and 10.0 ng/ml, 132 had BPH and 30 had prostate cancer. The specificity at 96% sensitivity for f/tPSA, f/cPSA and c/tPSA was 32, 44, and 41%, respectively. There was no significant difference in the area under the receiver–operating characteristic curves among fPSA/tPSA, fPSA/cPSA, and cPSA/tPSA in the overall PSA range or in tPSA between 4.1 and 10.0 ng/ml.Conclusion: fPSA/tPSA, fPSA/cPSA, and cPSA/tPSA did not differ in their ability to distinguish prostate cancer from BPH.