[Question #3481] Hiv tests 4 and almost 6 weeks
35 months ago
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H. Hunter Handsfield, MD
35 months ago
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35 months ago
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Questions:
1. Is a finger prick rapid test as accurate at 40 days as a laboratory test looking only for antybody ( for example - ELISA test) ?
2. Would a rapid finger prick test be 100 % conclusive for me at 8 weeks or need to wait for 3 months?
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H. Hunter Handsfield, MD
35 months ago
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35 months ago
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H. Hunter Handsfield, MD
35 months ago
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Interesting website; I was not previously aware of it. I can't say what database(s) is has used to create it's calculator, but 8% false negative result for the AgAb test at 28 days conflicts with the latest published summary of test peformance (which I linked in my last reply), which has been endorsed by CDC (https://www.ncbi.nlm.nih.gov/pubmed/29140891). Like Sean Cummings and Freedom Health, I have never had (nor heard of) any patient with negative 3rd gen HIV antibody test at 6 weeks, or negative AgAb test at 4 weeks, who later had a positive result and actually had acquired HIV at the exposure s/he was concerned about. On that basis, previously published data, and the policies of some experts (e.g. Freedom Health) and public health agencies, on this forum we considered 4 weeks conclusive for AgAb, but changed to 6 weeks when these publications became available. (In fact, they really say 45 days for conclusive results -- but we round that off to 6 weeks.)
You are correct in your seeming understanding that the data really aren't all that precise. If you think about it, you'll understand it's very hard to accumulate substantial numbers of at risk persons with only one possible exposure event and test them regularly (e.g. weekly) for several weeks or even 3-4 months. I'm not sure of the exact methodology that was used, but I think you're probably right that it's a combination of real patients plus mathematical modeling.
That concludes two follow-up comments and replies and so finishes this thread. I hope the discussion has been helpful. The bottom line is that you were at low risk of infection (the risk is always low, under one chance in hundreds, for even the highest risk sexual exposures), and with your current results you can be confident you weren't infected. A final AgAb test at 6+ weeks would be strictly for reassurance; I'm confident it would be negative.
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