SAN FRANCISCO — A promising new oral HIV test being considered for home use has produced at least 47 false positives at San Francisco public health clinics, throwing a scare into those who received the results and raising questions about the test's suitability for widespread use in the United States and abroad.
The OraQuick Advance HIV test approved for professional use by the Food and Drug Administration in March 2004 detects in just 20 minutes antibodies to the virus that causes AIDS, using fluid swabbed from the mouth.
Its speed and ease of use make the test a particularly suitable candidate for HIV prevention and treatment efforts that stress frequent testing and speedy access to care for those who test positive.
San Francisco Department of Public Health officials were alarmed last week when their analyses of more than 6,000 oral tests since spring turned up 47 instances in which the results were positive, but follow-up tests showed those patients were not infected.
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Dr. Jeffrey Klausner, the city's director of sexually transmitted disease prevention and control services, said about 1 out of 4 of the roughly 200 positives detected by the new oral test turned out to be wrong.
"We need to vigorously look at this," Klausner said. "You wouldn't want to have a home test with this problem."
He said there have been no known instances in which the oral test has missed an HIV infection that otherwise would have been detected by traditional blood screening. As frightening as a false diagnosis of HIV might be, a failure to detect a real infection would be far more dangerous.
The FDA is considering a request by Orasure Technologies, the Bethlehem, Pa., maker of the tests, to allow their over-the-counter sales. It would be the first HIV test available for home use that does not require mailing the sample to a laboratory to get results.
As a result of the spate of false positives, Klausner no longer uses the oral test at City Clinic, the health department's primary locale for testing for syphilis, gonorrhea and HIV.
He said he would like to have the mystery of why the tests failed resolved because he believes a reliable oral HIV screen would be a valuable tool. "I am not ready to discard this citywide," he said.
The San Francisco findings have been forwarded to the state Office of AIDS, the Centers for Disease Control and Prevention in Atlanta, and to the test maker.
In a telephone interview, Orasure Technologies chief executive Douglas Michels said no similar problems with the test have been reported outside of San Francisco. "We do not have any reason to believe our product is not performing to specification," he said. "We have every confidence that the test is reliable and accurate."
Data collected from thousands of oral tests conducted across the United States do not show the kind of problem described in San Francisco, he said.
