Officials report
high rate of false-positives on rapid HIV test

Health officials in San Francisco and New York City say they're getting an alarmingly high number of false-positive results on oral rapid HIV antibody tests given out during the past year, the San Francisco Chronicle reports. Jeffrey Klausner, director of sexually transmitted disease services for the San Francisco health department, says that of the roughly 200 positive results reported from the OraQuick rapid HIV tests given in the city, one quarter of them have been proven to be negative through follow-up testing.

In New York City, an average of about five false-positive results are reported from an estimated 3,600 to 3,700 tests given each month, which is within the accuracy rate predicted by test maker OraSure Technologies, reports New York City assistant health commissioner Susan Blank. However, 30 false-positive results were reported in November, well outside the accuracy window, Blank says.

The false-positive results are linked only with oral HIV antibody tests, officials say. The same rapid test kits also can be used with blood samples from finger sticks, and those results have been much more accurate, according to the San Francisco and New York City health departments.

The federal Centers for Disease Control and Prevention is expected this week to issue a public health advisory recommending that all positive results from oral OraQuick rapid HIV tests given nationwide be immediately followed up with finger-stick blood tests to confirm the results.

Because of the high level of false-positive results, San Francisco's City Clinic, the health department's main site for HIV and STD testing, is no longer using the tests, Klausner says. The AIDS Health Project in San Francisco also stopped using the tests after 28 positive test results detected there this spring proved to be false, says deputy director Joanna Rinaldi.

Some programs targeting hard-to-reach at-risk groups in San Francisco are still using the rapid HIV tests because of their ease of use and ability to provide results in just 20 minutes, Klausner says. "I'm not ready to discard this citywide," he told the Chronicle.

A statewide investigation is currently under way in California, and to date no other city has reported problems with the rapid tests, although results aren't yet in for Los Angeles County. San Francisco officials have reported their results to the Centers for Disease Control and Prevention, the state Office of AIDS, and OraQuick rapid HIV test maker OraSure Technologies.

OraSure officials say they have "every confidence that the test is reliable and accurate," the Chronicle reports. They also say that nationwide data show only 107 confirmed complaints of false-positive results from the oral rapid HIV antibody tests out of more than 28,000 given, resulting in an accuracy rate of 99.6%.

Researchers at the California Office of AIDS say they are not sure why so many San Francisco tests have resulted in false-positive diagnoses, but they speculate that there is something unique about San Francisco patients that is causing the false-positive results, possibly a high prevalence of hepatitis infection that causes a cross-reaction with the test. (Advocate.com)