Availability of the Free PSA Ratio Test
Li Liu, MD
Last Modified: November 1, 2001
Dear OncoLink "Ask the Experts,"
I recently read an article that states that the free PSA blood test is currently under study. What is the time frame for having this free PSA available to the physicians? What progress are they making?
Li Liu, MD, Editorial Assistant for OncoLink, responds:
Thank you for your interest and question.
In order to enhance the sensitivity and specificity of prostate cancer detection and reduce unnecessary biopsies in men with elevated prostate-specific antigen (PSA) levels, various assays have been established, including PSA density, PSA density of transitional zone, free/total PSA ratio, complexed/total PSA ratio, and PSA velocity. Several studies have demonstrated that the free/total PSA ratio test enhances the clinical usefulness of PSA testing for the early detection of prostate cancer.
Dr. Catalona from Washington University School of Medicine reported that free PSA may identify subgroups of patients with prostate cancer when their PSA values are between 2.52 and 4 ng/ml and digital rectal exam is not suspicious for cancer (Urology, 54(2): 220-224, 1999).
For patients with PSA levels between 4 and 10 ng/ml, percent free PSA also appears to be a strong predictor of postradical prostatectomy pathological outcome. (The Journal of Urology, 162:1346-1351, October 1999). Many physicians have used a cutoff of less than 15% for free PSA clinically as a reference to discriminate the likelihood of malignancy. The Free PSA assay is now available in most of the major medical centers in theUS. However, clinical judgments are made based on the entire scenario rather than one test alone.