The clinical value of the ratio of free prostate specific antigen to total prostate specific antigen.

Abstract

To examine the usefulness of the ratio of free prostate specific antigen (FPSA) to total prostate specific antigen (TPSA) in men with serum TPSA concentration of 4 to 10 ng/mL by using the cut off value of 0.15 for avoiding unnecessary biopsies. Two hundred thirty-six men aged between 52 and 91 with symptoms of prostatism were evaluated with digital rectal examination (DRE), FPSA and TPSA measurements. Patients with TPSA values under 4 ng/mL were biopsied if they had positive DRE and/or a FPSA/TPSA ratio lower than 0.15. All patients with TPSA values higher than 4 ng/mL were also biopsied. The predictive value and sensitivity of FPSA/TPSA ratio and TPSA alone were calculated. Eleven patients out of 170 with a TPSA value lower than 4 ng/mL were biopsied. Fifty-five patients had a value between 4.1 and 10 ng/mL. We performed transrectal ultrasound (TRUS) and prostate biopsy in these men except one patient. Biopsy proven prostate cancer was detected only in 12 patients. In this group of patients the predictive value of TPSA was 21%, but the predictive value of FPSA/TPSA ratio of 0.15 was 78% maintaining at least 90% sensitivity. Eleven of the patients had a prostate specific antigen (PSA) value higher than 10 ng/mL. In 6 of these patients the biopsy result was prostate cancer and 10 of these patients had a FPSA/TPSA ratio lower than 0.15. In patients with TPSA values between 4-10 ng/mL the cut off value of FPSA/TPSA ratio of 0.15 can be used to eliminate unnecessary biopsies with minimal loss of cancer patients.