The Role of Percent Free-Prostate Specific Antigen (PSA) in Patients with Total PSA Levels Between 4.0 and 10.0 ng/ml

Abstract

To explore the role of percent free-prostate specific antigen(PSA) on the differentiation between benign and malignant prostatic diseases in patients with serum total PSA levels between 4.0 and 10.0 ng/ml. Forty-three out of the 221 screened men who had total PSA levels between 4.0 and 10.0 ng/ml were retrospectively enrolled into this study. in addition to digital rectal examination(DRE), transrectal ultrasonography(TRUS), and total PSA, they received either TRUS-guided biopsies(n=27) or transurethral resection of the prostate (TUR-P) (n=16). All sample sera were then stored at -70 °C after the initial measurement of total PSA levels using an immunoenzymometric assay(Tandem-E®, Hybritech). Thereafter, all stored sera were quantified for free-PSA levels and total PSA levels using a different radioimmunometric assay(PSA-RJACT, CIS). Two values of percent free-PSA were obtained for each individual by dividing the same free-PSA level by 2 different total PSA values as measured by 2 different assays. Among the 43 patients, there were 34(79.1%) patients with benign prostatic hyperpla-sia(BPH), 5(11.6%) with prostatitis, and 4(9.3%) with prostate cancer(PC). Using these 2 different total PSA assays, the percent free-PSA in patients with BPH, prostatitis, and PC were 28.0%±12.2%, 23.6%±9.1%, 8.7%±1.3% (FPSA-RJACT/Tandem-E®) and 29.6%±13.1%,28.5%±13.1%, 9.7%±1.1% (FPSA-RJACT/PSA-RIACT), respectively. Patients with PC had significantly lower values of percent free-PSA (less than 12%) while those with either BPH or prostatitis had values greater than l2%(p values, 0.015 and 0.003, unpaired t-test). In contrast, the percent free-PSA values were not statistically different between BPH and prostatitis patients in both assays (p=0. 44, unpaired t-test). Besides, the correlation between the 2 values of percent free-PSA was good(r2 =0.90), based on 2 different assays for total PSA levels. Our study implies that percent free-PSA can help differentiate prostate cancer from benign prostatic diseases, and thus greatly reducing unnecessary biopsies. There is no need to measure the total PSA levels again while determining the percent free-PSA.