Oral HIV Tests Not the Last Word
A high number of false positive results means these tests are only preliminary screen, experts say
THURSDAY, Dec. 15, 2005 (HealthDay News) -- When an HIV test tells someone they are infected with the virus that causes AIDS, most would probably assume that's the end of the story.
However, as doubts emerged this week as to the accuracy of one rapid oral HIV test, experts noted that "false positive" results aren't as rare as people might think.
In fact, doctors consider a result on the oral HIV test to be only a preliminary finding, because of the risk that the screen may be inaccurate. Most physicians routinely advise patients to go for a more accurate HIV test if they turn up positive.
"That's the standard protocol across the U.S.," said Dr. Jeffrey Klausner, director of STD Prevention at the San Francisco Department of Public Health. "Unfortunately, most test counselors and patients don't really know what 'preliminary positive' means, and they interpret the results as positive."
HIV testing is in the news because health officials in San Francisco and New York City reported that a rapid oral-fluid test known as OraQuick turned up numbers of incorrect results, suggesting that dozens of people thought they were HIV-positive when they weren't.
The complaints are especially newsworthy because federal officials are considering whether to allow the OraQuick test to be sold over-the-counter, meaning that Americans could instantly test themselves for HIV in their own homes. (In-home HIV tests are available now, but they require users to send blood samples in for testing.)
In San Francisco, follow-up tests determined that about 47 of 200 positive OraQuick tests were actually negative, Klausner said. That means about 25 percent of the HIV-positive results turned up by the test were incorrect.
In New York City, according to news reports, the number of reported OraQuick false positives jumped from 10 in October to 30 in November.
The OraQuick oral test received federal approval in March 2004. Traditional HIV tests require blood samples, but OraQuick users only need to stick a digital-oral-thermometer-like device in their mouths. A porous pad comes into contact with the area between the cheek and gums, gathering oral fluid. Then users stick the pad into a test chamber to get the result.
Orasure, the Pennsylvania company that produces the test, hasn't been able to explain the rash of false positives, which sent the company's stock price tumbling this week. Chief Executive Officer Douglas Michels said "these appear to be isolated reports," and he pointed out that the tests are highly accurate at detecting HIV when it's actually present.
According to the San Francisco Chronicle, the U.S. Centers for Disease Control & Prevention plans to issue an alert advising doctors to immediately confirm a positive oral HIV test with a follow-up blood test, and then send for results of a third blood test that is more conclusive but time-consuming.
It's unclear whether the current bad publicity will affect the federal government's review of Orasure Technology's proposal to offer OraQuick over the counter. In the past, there was concern about in-home HIV tests because of the prospect that people who turned up positive would become upset and possibly commit suicide; some specialists say those concerns have lessened as AIDS has become a more treatable disease.
Michels said the test should always be seen as purely for "screening," not as a definitive indication of HIV infection.
Learn more about oral HIV tests from womenshealth.gov.