Posted on 12/09/2005 7:47:51 PM PST by neverdem
Associated Press
SAN FRANCISCO -- A promising new oral HIV test that uses fluid swabbed from the mouth to quickly and easily detect the virus that causes AIDS incorrectly diagnosed a quarter of the people who tested positive in San Francisco, city health officials found.
Forty-seven people who tested positive after using the OraQuick Advance HIV test in city clinics were not infected at all, the San Francisco Department of Public Health said this week.
Investigators learned of the errors after follow-up blood screenings gave the patients a clean bill of health, and health officials stopped using the test at City Clinic, the health department's primary testing location for HIV.
At the same time, the U.S. Food and Drug Administration, which approved the OraQuick test for professional use last year, is now considering a request from drug maker Orasure Technologies, of Bethlehem, Pa., to approve it for home use and over-the-counter sales.
"We need to vigorously look at this," said Jeffrey Klausner, San Francisco's director of sexually transmitted disease prevention and control services. "You wouldn't want to have a home test with this problem."
Klausner said there are no known instances in which the test missed an HIV infection that a traditional blood screening would have caught.
Orasure Technologies chief executive Douglas Michels said San Francisco is the only city that has reported the problem, and data collected from thousands of oral tests conducted in cities across the country show the test is reliable.
A statewide survey by the California Department of Health Services that was prompted by the San Francisco findings has not yet found a similar problem.
"We do not have any reason to believe our product is not performing to specification," Michels said. "We have every confidence that the test is reliable and accurate."
One explanation for the spate of false positives might be that there is something something unique about the San Francisco group, such as a high number of people with hepatitis, that may unexpectedly interfere with the test results, said Deanne Sykes, a research scientist for the California Office of AIDS.
"We will watch it," she said. "We will monitor it to see if there is something consistent we can pinpoint."
If this is meant to be used as a screening test, as ELISA is, then there will always be false positives. But I'll try to figure out the sensitivity and specificity based on what little information is given.
... Michels said. "We have every confidence that the test is reliable and accurate." ...
Gee, Is someone in denial?
I'm no scientist, but I have to say that a test giving 25% false positive results is a pretty subpar test.
I take that back, I can't figure sensitivity and specificity out because I don't know how many people were tested to begin with. Funny how the article doesn't give enough information for us to be able to tell if this is just a matter of screening tests having low specificity, or if it's simply not a very good method of testing for HIV.
25% false positive may not be bad for a screening test. The purpose of a screening test is not necessarily to definitely detect disease, but to determine who must undergo more intense (and more expensive) testing. Screening tests always have more false positives than "gold standard" diagnostic tests, and this is tolerated because it's considered better to have an initial false positive than a false negative, in which the patient has the disease but it is never detected by the screening test, and so they go undiagnosed. In order to know if the test is actually a good one, we would need to know how many total were tested, or at least how many false negatives occur.
I will stipulate to the truth of your post, and second it with a hearty "What you said!"
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Uh, so? LOL
If you don't take it up the wazoo, and don't date messed up women, you really don't have to worry.
I've had to work with these freaks, and because they're so messed up mentally to begin with, they've caused me plenty of anxiety.
Payback is Hell.
God reigns!
So, why is "negative" good news, and "positive" bad?
That would depend on its application and presentation. This same test gave no false negatives.
If this test is being given as an inexpensive screening device to reduce the need for widespread, sophisticated testing it is serving its purpose. The problem seems to lie in the presentation of the test by the clinics. There appears to a belief on the part of the clinic's clients that this test is comprehensive and not simply a step along the way, indicating the need for more accurate and expensive testing.
Better to have a false positive and do a further workup, than have a false negative, and take that as the final result...
I agree, but when you're dealing with something like AIDS, we're talking serious emotional trauma.
I was given what turned out to be a false positive for hepatitus when I gave blood. Kind of creeped me out even though I had none of the usual risk factors. Of course they handled it with the sensitivity of a brick in the face when they notified me with an incomprehensible letter.
Apparently false positives are high, but I think, among other reasons, it is a cheaper test. Interestingly, even though I tested negative later with a much more accurate test, I will not be allowed to give blood again. In spite of having fairly uncommon blood type.
Yup. And better to have a false positive than a true positive. So while I can understand that the individuals with false positives would experience anxiety before they got a negative on their Western Blot, would they really prefer the alternative?
I understand that. However, it is impossible to have a test that is both 100% sensitive and 100% specific. That's why there are different levels of tests, and why some are used for screening (sensitive but not specific) and some are used for definitive diagnosis (very specific but not as sensitive).
And not to sound terribly cruel, but in the case of this specific disease, anyone who doesn't want to experience such anxiety before the initial positive is confirmed either true or false can simply not have sex with people they don't know and not use intravenous drugs.
25% is probably way too high for a home health test. I foresee many lawsuits, perhaps over false-positives suicides. The general public are stupid and would panic although it might be nice for heterosexuals and homosexuals have these available to them before anonymous encounters.
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