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As I said before, the antibody tests are being used to diagnose infection, whereas even the manufacturers do not claim that their products can detect the presence or absence of HIV in a sample. The same is true of the other tests that look for fragments; neither the p24 assay nor the viral load or bDNA tests have been approved by the FDA for diagnosing HIV infection. They’re not even intended to diagnose HIV infection.
Typical Disclaimers from HIV Test Manufacturers "EIA testing alone cannot be used to diagnose AIDS, even if the recommended investigation of reactive specimens suggests a high probability that the antibody to HIV-1 is present. [...] At present there is no recognized standard for establishing the presence and absence of HIV-1 antibody in human blood. Therefore sensitivity was computed based on the clinical diagnosis of AIDS and specificity based on random donors"1 "Do not use this kit as the sole basis of diagnosing HIV-1 infection"2 "The Amplicor HIV-1 Monitor test is not intended to be used as a screening test for HIV or as a diagnostic test to confirm the presence of HIV infection"3
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Zenger’s: So why do the tests not work to diagnose HIV infection? What about them limits them so they cannot accomplish that?
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Dr. Richards: I would be in disagreement with that. I think that, had it been done once or twice, with several hundred or several thousand samples that show that there indeed is a correlation, then I would say fine. Let’s go on with life. You’ve proven to me, or you’ve convinced me, that these
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"I repeat we did not purify." |
test correlates with the actual presence of the virus. This is how most diagnostic products are developed. Once or twice, or maybe three times, we have to prove that the test result, regardless of what it’s based on, correlates with the actual germ or pathogen in the sample.
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It turned out that at least 50 percent of these people who were ELISA-positive also had antibodies to one or more of the nine bands on Western Blot. I don’t know if you want me to explain what bands are,
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Western Blot |
but it’s a series of proteins on a strip of paper, and if antibodies stick to those proteins, it does something called “light up,” which means it becomes visual.
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So this presented a very big dilemma. Why were test results in the Gay community and IV drug-using community being declared positive, when the exact same test results in healthy blood donors were being called — well, there wasn’t really a term for it. It was just, “We don’t know.” The same tests results in healthy blood donors were meaningless; and yet in the risk groups they were said to be “confirming infection.”
"The risk of an asymptomatic person with a repeatedly reactive serum sample developing AIDS or an AIDS related condition is not known." "The clinical implications of antibodies to HIV-1 in an asymptomatic person are not known."
2, Cambridge Biotech Corp. Rockville, Package insertMaryland, U.S. License No. 1063. 6/2/98 |
Zenger’s: I’ve heard that argument before, and one of the arguments I’ve heard the mainstream make against it is that, at least in California and some other states as well, HIV testing is available anonymously. When the sample goes to the lab, it’s supposed to be identified only by a number, and they’re not supposed to have any idea where that number came from. So therefore they would have no way of knowing whether this came from a Gay man, or an IVDU, or a healthy blood donor, or anybody. They would have no way of doing this kind of social screening that you’re talking about.
Dr. Richards: You’re saying that there would be no way to bias the results to a “positive” for a risk-group member, if I understand you correctly. And that’s true. What eventually happened to resolve this problem was that different institutions — public-health institutions, government institutions, whatever — developed something known as “evaluation criteria” for Western Blot. That means that instead of just looking for antibodies to HIV proteins on the Western Blot, they look for combinations of banding patterns.
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HIV Positive? Depends where you live |
And they chose combinations that minimized the numbers of blood donors testing positive and maximized the numbers of people in risk groups testing positive.
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The bDNA looks directly for the genomic material — or the genomic fragment, I should say. When I say “genome,” that means the complete set of DNA — or, in this case, RNA — for the virus. Therefore it’s less prone to problems in the testing lab. But it still does not prove the presence or absence of a virus in a sample. All that it’s looking for is the presence or absence of a fragment of genetic material believed to be unique to HIV.
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A shorter version of this article appears in the October 2001 issue of Zenger’s Newsmagazine. address: P.O. Box 50134, San Diego, CA 92165 phone: (619) 688-1886 mgconlan@earthlink.net