Sunday, December 02, 2007
Day After World AIDS Day Blogging
Throughout all the NPR coverage of World AIDS Day, everyone was emphasizing something over and over again: the need to be tested and to know your HIV status. Except one problem. AFAIK, when they test an individual(*) they test for the presence of antibodies that can take up to (or even longer than) 3 months post infection to show up(**). So, even though I am sure that they warn people about this, how many people are tested yet don't know their HIV status ... or worse think they are HIV negative when the really aren't?
And why did no-one mention this? Do they now routinely use a PCR based test for HIV? Is what I "know" incorrect or at least out of date? Or are people really forgetting about the time it takes for those with HIV to seroconvert? It seems to me that if knowing your HIV status is important to the fight against AIDS, that so many people might have a negative HIV test yet still be infected 'cause they haven't seroconverted would be a big issue, wouldn't it?
*for the blood supply, where they only expect a limitted number of samples to have HIV, they can pool samples, do a direct PCR-based test for the presence of HIV and then divide and conquer to determine which sample in the pool has the virus if any do ... thus cheaply and effectively eliminating HIV from the blood supply. But such an approach'll only save tests if relatively few samples have HIV. In the case of personal testing, you have "adverse selection" (a parable for health coverage is here somewhere) so you'd end up having to test pretty much every sample for HIV anyway, which would be hella expensive on a per sample basis.
**which says something about the immune response to HIV. nu? it indicates how difficult it'll be to fight the infection immunologically when it takes the immune system so long to figure out it has a problem anyway ... of course with HIV the whole issue is indeed quis custodiat ipsos
custodes at an organismal and even cellular level
And why did no-one mention this? Do they now routinely use a PCR based test for HIV? Is what I "know" incorrect or at least out of date? Or are people really forgetting about the time it takes for those with HIV to seroconvert? It seems to me that if knowing your HIV status is important to the fight against AIDS, that so many people might have a negative HIV test yet still be infected 'cause they haven't seroconverted would be a big issue, wouldn't it?
*for the blood supply, where they only expect a limitted number of samples to have HIV, they can pool samples, do a direct PCR-based test for the presence of HIV and then divide and conquer to determine which sample in the pool has the virus if any do ... thus cheaply and effectively eliminating HIV from the blood supply. But such an approach'll only save tests if relatively few samples have HIV. In the case of personal testing, you have "adverse selection" (a parable for health coverage is here somewhere) so you'd end up having to test pretty much every sample for HIV anyway, which would be hella expensive on a per sample basis.
**which says something about the immune response to HIV. nu? it indicates how difficult it'll be to fight the infection immunologically when it takes the immune system so long to figure out it has a problem anyway ... of course with HIV the whole issue is indeed quis custodiat ipsos
custodes at an organismal and even cellular level
# posted by alberich @ 2:34 PM 
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The antibodies *can* take up to three months to appear but most often appear within weeks of infection, and there are equivocal results which are then followed automatically by PCR testing (automatically meaning the lab does it immediately on the same specimen). Still not perfect - ideally people at risk should be tested twice, with the second test coming at least six months after the most recent possible exposure, or every six months if there's ongoing risk.
Jay,
Thank you for your expert response.
ideally people at risk should be tested twice, with the second test coming at least six months after the most recent possible exposure
Do you think the word is getting out about this? How much do you think "well, I got tested and the test says I'm negative" said by people who turn out to be positive (and ignored the mention of retesting) is an issue?
Also, AFAIK, some organizations say different things about how long to wait ... some say 3 months, some say 6 months, some say 1 year. If indeed the 6 monthers are right ... what is the likelihood that someone who's been told 3 months is really positive even if s/he thinks s/he's negative and is spreading the disease?
Additionally -- are cases where people test negative for HIV (because they got tested too soon and didn't know they needed to get retested) and then develop AIDS adding fuel to the fire of those who deny HIV causes AIDS?
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Thank you for your expert response.
ideally people at risk should be tested twice, with the second test coming at least six months after the most recent possible exposure
Do you think the word is getting out about this? How much do you think "well, I got tested and the test says I'm negative" said by people who turn out to be positive (and ignored the mention of retesting) is an issue?
Also, AFAIK, some organizations say different things about how long to wait ... some say 3 months, some say 6 months, some say 1 year. If indeed the 6 monthers are right ... what is the likelihood that someone who's been told 3 months is really positive even if s/he thinks s/he's negative and is spreading the disease?
Additionally -- are cases where people test negative for HIV (because they got tested too soon and didn't know they needed to get retested) and then develop AIDS adding fuel to the fire of those who deny HIV causes AIDS?
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