NEW YORK (Reuters Health) - Testing for the (-2)-isoform of proenzyme prostate specific antigen (p2PSA) is more accurate than PSA testing in differentiating prostate cancer from benign disease, according to a report in the April issue of The Journal of Urology.
"There may soon be a commercially available blood test for prostate cancer screening that is more accurate than what we currently have," Dr. William J. Catalona from Northwestern University, Chicago, told Reuters Health by email.
Dr. Catalona and colleagues assessed the value of p2PSA and the Beckman Coulter prostate health index (phi), which combines PSA, free PSA, and p2PSA, for detecting prostate cancer in 63 men who underwent prostate biopsy for a total PSA between 2.5 and 10 ng/mL.
All had benign findings on digital rectal examination, but 41% had prostate cancer on biopsy with a Gleason score of 6 or 7.
Total PSA did not differ significantly between men with positive and negative biopsies, but men diagnosed with prostate cancer had a significantly lower median percent free PSA and a higher median percent p2PSA.
The percent of positive biopsies increased continuously with increasing percent p2PSA tertile, the report shows.
Percent free PSA, percent p2PSA, and the Beckman Coulter prostate health index had more favorable performance characteristics than did total PSA alone, the researchers note, and percent p2PSA outperformed percent free PSA and total PSA when the sensitivity level was set at 88.5%.
The Beckman Coulter prostate health index score improved diagnostic performance to a greater extent than did the other parameters examined.
"Due to the small sample size of men undergoing prostate biopsy, these promising findings will ultimately require validation in larger populations," the investigators say. "If confirmed, our results suggest that p2PSA alone or in combination with total PSA and free PSA may help reduce unnecessary biopsies, since only 12% of biopsies were positive at a percent p2PSA less than 1.36%."
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