HIV CMIA Ab - Ag Combo Test
Dec 19, 2011
Hi Dr. Richard, In a high risk exposure with ARS symptoms, if an HIV CMIA Antigen and Antibody Combo Test is taken at 7 weeks, what is the reliability of the test? 1. Is it true that sometimes in an infected person, both antigen and antibodies can be below reactive levels at 7 weeks and thus can give a false negative? 2. Is it true that at least either one of Ab or Ag has to be positive at 7 weeks in an infected person? 3. Have you seen anyone testing negative at 7 weeks and then positive at 13 weeks? Regards
Response from Mr. Cordova
Thanks for writing in. Since most people will show up positive on an antibody test by 25 days. It's likely that at seven weeks, it would be fairly reliable. However, antigen tests are not used as stand alone tests and a conclusive (negative) test could be obtained at the 90 day mark.
1. The antigen test has a more limited window of accuracy, so while it is possible that at seven weeks it would be too late for an accurate antigen test, a person would likely have produced enough antibodies to get an accurate result on an antibody test. However, the three month window for a conclusive negative result stands.
2. No, but it is likely.
3. I have not personally, but it is possible.
I hope this helps.
In health, Richard
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