DOCTOR'S VIEW ARCHIVEROCKVILLE, MARYLAND--On August 6, 1996, the Food and Drug Administration approved the first HIV test that uses urine samples. All previously approved HIV tests use either blood or oral fluid samples.
The new urine-based test detects the presence of antibodies to HIV-1, the virus that causes the vast majority of U.S. AIDS cases, using an enzyme linked immunosorbent assay (ELISA) method.
The test is approved to screen for HIV-1 infection and may be useful for medical purposes when the collection of blood samples is impractical.
The test is manufactured by the Calypte Biomedical Corporation of Berkeley, Calif., and will be marketed as the Calypte HIV-1 Urine EIA. It will also be marketed by Seradyn Inc. of Indianapolis, Indiana as the Seradyn Sentinel HIV-1 Urine EIA.
The test can be ordered only by a physician. Samples will be analyzed in certified medical laboratories. Any initially reactive sample will be retested twice. If even one of the second tests is reactive, the screening test will be considered positive, although this positive result does not always indicate HIV infection.
For confirming a positive screening test, anyone testing positive with the Calypte test must be retested with a more accurate test using a blood sample.
A patient information sheet provided with the new test will outline the limitations of urine HIV-1 testing in addition to the usual information on HIV and AIDS provided to people before HIV testing. After reading the information sheet, the person being tested will initial the statement confirming the receipt of the pre-test counseling, peel off the sample label and apply it to the urine collection cup. FDA's approval was based on clinical studies demonstrating that the test is sufficiently accurate for screening in medical and public health settings. The urine-based ELISA test is not approved to screen blood donors. For that purpose, more accurate ELISA tests using blood samples are required.
In the clinical studies, urine and blood samples were taken from 298 patients diagnosed with AIDS and tested with both the Calypte HIV-1 Urine EIA and a licensed ELISA test using a blood specimen. The urine test was positive as an initial screening test 99.3% of the time in persons known to have AIDS. In asymptomatic HIV-1 infected patients, the test would be expected to miss 1 or 2 people in every 100.
Other studies showed that the urine-based test would give a falsely positive result in one or two people out of 100 without HIV-1 antibodies in their blood, compared to one in 1000 with a blood-based ELISA test.