[Question #6662] Rapid test window period

12 months ago
Dear docs, 
sorry if my English isn’t perfect, I’m writing you from Italy, after unprotected vaginal exposure I took a rapid hiv antibody test approved in Europe at about 11 weeks after the exposure, exactly 75days. The test manufacturer says the conclusive results are after 12 weeks. Can I consider my negative test conclusive after 75 days or is too early? Here is the link to the mentioned test: 


Regards


H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
12 months ago
Welcome to the forum. Thank you for your confidence in our services.

I am not personally familiar with this test, but presumably it is a modern antibody test (i.e. 3rd generation) or perhaps an antigen-antibody test (AgAb, i.e. 4th generation). All AgAb tests are conclusive any time after 6 weeks, and most or all 3rd generation antibody tests by about 8 weeks, and most people have positive results by 4-6 weeks. Therefore, I would consider your result conclusive. I see the manufacturer states 3 months, but that probably is conservative.. 

Even if not quite conclusvive at 75 days, you should be satisfied with the result and confident you didn't catch HIV. The infection risk from a single episode of unprotected vaginal sex with an HIV infected women averages about 1 in 2,500; and probably you don't know your partner is infected, so your risk probably is even lower. So even if we consider your result to be maybe ~99% conclusive, the chance you have HIV almost cxertainly is well under 1 in a million. However, if you feel you need 100% certainty from the test itself, it would be reaasonable to have another test a full 3 months (90 days) after the exposure. But stay relaxed in the meantime:  almost certainly you don't have HIV.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD
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12 months ago
Thanks for your clarifications, I’ve seen that the test is the European version of the clear view test sold in US. Same principles 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
12 months ago
ClearView is estimated to detect 99% of infections by 58 days. It's safe to assume it detects all infections by 75 days.---
12 months ago
Thanks, the test is a 3rd generation one then as you stated multiple times in your previous forum too the negative results after the 8th week should be conclusive. For peace of mind(I hope) I will test again after 12 weeks but I think I can hope that  everything’s fine 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
12 months ago
All data on test performance are "soft":  the power of statistics to prove 100% test sensitivity at various times is limited. (There are no studies of the thousands of cases that would require, and most test data are estimates on the basis of only a few hundred patients at best.) In other words, all cited data are a combination of rough statistics plus expert opinion based on the known biology of HIV, antibody production, etc. As for Clearview performance, 8 weeks is 56 days, consistent with my comment above about 99% reliability by 58 days. Don't split hairs between 99% and "conclusive". Feel free to test again if you wish, but my guess is that there has never been anyone who tested negative at 75 days with a 3rd generation test and turned out to have HIV, with a positive later test. You won't be the first -- do your best not to worry.

That completes the two follow-up exchanges included with each question and so ends this thread. I hope the discussion has been helpful. Bet wishes and stay safe.
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