Evaluation of the diagnostic use of free prostate specific antigen/total prostate specific antigen ratio in detecting prostate cancer.

OBJECTIVE To assess whether Free/Total prostate specific antigen (PSA) would enhance prostate cancer detection in men with total serum PSA between 2.5 and 10 ng/ml. METHODS This case control study was conducted in the Department of Urology and Renal Transplantation, Jinnah Hospital, Lahore from January 2001 to June 2004. A total of 200 consecutive patients with symptoms of prostate disease, age 60 years or above, and serum PSA level 2.5 to 10.0 were included. Before trans-rectal biopsy of the prostate, a blood sample was taken and total and free PSA levels measured. The results were correlated with biopsy results. All patients had signs of benign prostate disease on digital rectal examination. As a second part of the study, we estimated free prostate specific antigen/total prostate specific antigen ratio (FPSA/TPSA) in 100 local age-matched population who presented to our department with diseases other than that of prostate. RESULTS Of the 200 patients included in the study, 122 had free/total prostate specific antigen ratio (FPSA/TPSA) > 0.18 and 78 patients had < 0.18. Of the later 78 patients, 68 (87%) had cancer. Six of the 122 patients showed malignancy on biopsy. In regard to free/total prostate specific antigen ratio there was statistically significant difference between prostate cancer and benign prostate hyperplasia (p < 0.001). The sensitivity and specificity of the FPSA/TPSA ratio were 91.9% and 92.1% respectively with 87.2% positive predictive value. The mean total PSA for the benign prostates hyperplasia, prostate cancer and control group were 6.5, 7.2 and 5.2 respectively. FPSA/TPSA ratio in the control group was > 0.42. CONCLUSION Free to total PSA ratio improves early detection of carcinoma of prostate and prevents the patients from unnecessary biopsy.