( of care use to mail-in specimen collec...)PSA TestingHow Much is Too Much?,Health

Bio-Quant, Inc., San Diego, Calif., manufactures the OneStep PSA InstaTest designed to detect PSA concentration in whole blood or serum in concentrations as low as four ng/ml within 15 minutes. The result is read visually by observing symbols that develop during the test in a result window. The company says that comparative studies have demonstrated that relative sensitivity of InstaTest PSA is 100 percent, and its relative specificity is 98.5 percent.

Beckman Coulter, Inc., Fullerton, Calif., produces the Hybritech PSA Test and, as a confirmatory follow-up, the Hybritech free PSA Test. The Hybritech PSA test was the first assay approved by FDA for the detection of prostate cancer when used in combination with digital rectal examination (DRE) in men aged 50 years or older. The assay provides equimolar PSA measurement based on a monoclonal antibody pair. The company lists analytical sensitivity at <0.008 ng/mL ; measurement range to 150 ng/mL and precision at < 5% CV across the assay range. Time to first result is 20 minutes, using a serum sample of 25 L.

In the early 1990s, it was demonstrated that measuring the ratio of free to total PSA could further help in distinguishing prostate cancer from benign prostate disease. The Hybritech free PSA testalso the first test of its kind to receive approvalhelps determine the percent of free PSA and thereby improve the accuracy of prostate cancer detection while eliminating a projected 20 percent of all prostate biopsies . The free PSA test is used following a non-suspicious DRE and a total PSA test that shows moderately elevated PSA levels (between four and 10 ng/mL) in men aged 50 years and older.

Analytical sensitivity for this assay at <0.005 ng/mL ; measurement range to 20 ng/mL and precision at '"/>