Various Tests and Accuracy???
Nov 16, 1998
With the various tests for HIV that I'm aware of and those I am not, could you please answer a few questions for me? I would like to know the point in time that the following tests are most reliable and the corresponding accuracy rating on them as well. (HIV antibody testing, Home Access testing, P24 Antigen testing, DNA/PCR testing and any other test out there that can also be used to rule out infectiond) And, why does the CDC always recommend antibody testing vs. PCR viral load testing? I was told the accuracy is better with waiting the six months and having the standard ELISA test. Please offer some information on this. THANKS.
Response from Dr. Holodniy
Home Access testing is a standard HIV antibody, then western blot confirmation of HIV antibodies. This test is most reliable about 12 weeks after acute HIV infection(when antibody testing is >99% accurate. The studies were done in HIV infected patients with chronic infection. It was 99.9% accurate. P24 antigen becomes positive we think after about a week. It has a very short window of positivity. It may be gone within a few weeks (usually when antibody develops), or sooner. Blood cell DNA PCR testing is a yes/no test. It is usually positive within several days to a couple of weeks after infection. In small studies using kits, it's very accurate. Viral load testing can also be used. It is positive in virtually all patients within several days after infection. PCR and/or viral load testing are not FDA approved for HIV diagnosis. The standard algorithm is still do do antibody testing out to 6 months (even though 99% will seroconvert within 3) to be sure that all patients will be detected.
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