The percentage of measured prostate-specific antigen (PSA) existing in the free form (free:total PSA ratio) is useful in assessing the risk of prostate cancer in patients with borderline or moderately increased total PSA (4.0-10.0 ng/mL) and has been used to help select men who should have follow-up prostate biopsy. Most prostate cancers are slow growing, so the utility of prostate cancer screening is marginal in most men with a life expectancy of <10 years.The test is done to screen men for prostate cancer, to help determine the necessity for a biopsy of the prostate, to monitor the effectiveness of treatment for prostate cancer, and/or to detect recurrence of prostate cancer. PSA, a protein produced by prostate gland cells, circulates through the body in two ways: either bound to other proteins or on its own. PSA traveling alone is called free PSA. The free-PSA test measures the percentage of unbound PSA; the PSA test measures the total of both free and bound PSA.