Conflicting Information Regarding PCR Testing
Aug 6, 1998
Approximately two weeks ago I had a potential exposure to the virus through unsafe sex. I have been ridden with anxiety and have been trying to determine the best test vehicle. I've read conflicting information on PCR Testing. I called the CDC and was referred to a HIV testing center (private organization) that claims the PCR Qualitative Test is 99.9% conclusive after 28 days. I have read your responses to PCR testing but Mr. Sowadsky recommends against PCR testing (reason = indeterminate) in favor of the antibody test. Should I do an antibody test at 4weeks in addition to a PCR test. The NYState Dept of Health says that antibody tests at 4 weeks are 95% conclusive while The Body recommends a 6 month window. This anxiety is exhausting.
I am confused about the conflicting information, can you please help me understand?
Response from Dr. Holodniy
I understand your concern. I am not sure that all the information you have received is contradictory. In fact, it all fits together. Standard testing strategies call for antibody testing by ELISA and western blot at about 1, 3, and 6 months after exposure. If one is using just antibody testing, the majority of people will have positive tests at 4-12 weeks after exposure. A small minority of people will not and take longer to seroconvert. That is why the 6 month test is done. It is extremely rare for antibodies to develop after 6 months of exposure. Tests which actually measure the virus plasma viral load (not FDA approved for diagnosis) or cell DNA PCR, can be positive within a couple of weeks after infection and > 99% are positive by 4 weeks. If commercial labs perform these tests using kits manufactured by the major test making companies, they are very accurate. If the lab uses a "house test", it may not have the accuracy. A negative antibody at 4 weeks may not rule out infection. A negative viral load test at 4 weeks after exposure is pretty reliable. I would still proceed with standard testing strategy out to 6 months. Good Luck.
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