Free and total prostate specific antigen in benign prostate hyperplasia and prostate cancer

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.

A cross-sectional, case control study.

Shaikh Zayed Hospital and Mayo Hospital, Lahore from August 2002 to March 2003.

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.

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%.

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.