Free and Total Prostate Specific Antigen in Benign Prostate Hyperplasia and Prostate Cancer

Abstract

OBJECTIVE: To record the levels of PSA in the sera of prostate cancer (CaP) and benign prostatic hyperplasia (BPH) cases. Free PSA/total PSA as percentage was also calculated in order to evaluate its utility in differentially diagnosing BPH and CaP.

DESIGN: A cross-sectional, case control study.

PLACE AND DURATION OF STUDY: Shaikh Zayed Hospital and Mayo Hospital, Lahore from August 2002 to March 2003. Materials and Methods: A group of 108 male subjects, including one-third of each of biopsy-confirmed prostate cancer cases, BPH cases and asymptomatic controls of matching age were studied. PSA and Free PSA were determined by ELISA using commercially available assay kits.

RESULTS: Mean PSA was found to be highest in CaP cases (41.9 /- 38.7 ng/ml), lower in the BPH cases (13.5 /- 10.5 ng/ml), while it was lowest in the control subjects (5.7 /- 4.4 ng/ml). Moreover, it was observed that a majority of the CaP cases had serum PSA >20 ng/ml, 50% of BPH cases had serum PSA in the 'gray zone' (4.1-20 ng/ml), while majority of controls had serum PSA in the 'normal' range (0 - 4 ng/ml). Using a free- PSA "cut-off" of 18% to differentiate between benign and malignant prostate enlargement, it was found that 80% of the CaP cases had F/T% <18, while 75% of the BPH cases had F/T%>18. The percent free-PSA test to differentially diagnose BPH and CaP in the 'gray zone' was found to have a sensitivity of 86% and a specificity of 94%.

CONCLUSION: Using a cutoff of 18%, the free-PSA test significantly improved the differential diagnosis of BPH and CaP in the 'gray zone' as compared to the use of total PSA alone in the study group.