[Question #1420] Accuracy of test and window period, 21 days

46 months ago

Dear Doctors,

I had an encounter with a professional sex worker 24 days ago. We had protected sex for everything: oral and vaginal.

When I was pulling out though most of my penis (95%) was out of the condom and the condom itself was hanging from her vagina. I also noticed some blood on the outside of the condom, most likely menstrual blood. I do not think that it slipped while I was inside, only when pulling out, but I cannot be 100% sure.

I asked the girl and she told me she was tested two weeks before and that her tests came back negative for all STDs, including HIV.

I completed two tests on day 21: a rapid bioLytical INSTI HIV-1/HIV-2 antibody test and a 4th generation duo (ab/ag) regular blood test. Both came back non reactive.

I know that none of those can be considered fully conclusive but do you think that they are useful at that point and that they are a good indication that I am and will remain HIV-? What would be your recommendation for further testing? 6 weeks with another duo test? I would also take the opportunity to get tested for other common STIs as well (I already got tested for chlamydia and gonorrhea and all was fine).

Thank you very much for your time!

Edward W. Hook M.D.
Edward W. Hook M.D.
46 months ago

Welcome to the forum.  I'll be please to comment.  If your question involved whether to test or not I would have told you that nothing about the exposure that you describe suggests you are at risk for any STI, including HIV.  There is a long list of reasons that I say this including that most commercial sex workers are not infected, that only a small proportion of even unprotected exposures lead to infection, that your partner said she was not infected and most people do tell the truth about such things, and most importantly that your exposures were condom protected.  Even when condoms "stay behind" upon withdrawal, they typically have done their job, preventing infection.

But, you asked about test performance.  While I am confident that the exposure you describe did not result in exposure to any STI, no matter when you test,  That facts on test performance are that your HIV-1/-2 antibody test at three weeks would detect well over 2/3 of recent infections and your 4th generation test would have detected about 90-95% of infections but not quite all.  If you must test (not that you need it) a repeat 4th generation test at any time more than 4 weeks after your exposure will provide completely reliable test test results, validating my statement that you are not at risk for HIV. 

I hope my comments are helpful to you. EWH

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46 months ago
Thank you very much for your answer doctor. I believe and trust you when you say that the risk is pretty much non existent. Just for my peace of mind though, I think I will retest at 6 weeks to be able to turn the page on this event.
Just one last question, is 6 weeks an appropriate time to test for the most common STIs or would you recommend another moment?
Edward W. Hook M.D.
Edward W. Hook M.D.
46 months ago
You indicated you have already tested for Gonorrhea and Chlamydia - no further testing is needed.  Blood tests for Syphilis or hepatitis B will be reliable at any time more than four weeks after your exposure  although very rarely these tests can take up to three months to become positive. We strongly recommend against blood tests for herpes as your risk of a falsely positive test is higher than your risk of diagnosing a newly acquired infection.  EWH---
46 months ago
Thank you very much all your answers! Have a wonderful weekend!