[Question #6596] possible exposure and antibody test at 6.5 weeks

66 months ago

Hello

I had unprotected sex with a woman from United Kingdom of unknown hiv status. She told me after that she does not have hiv or any other STI and got tested last year for it and has been with one person since then. Out of concern, and due to the fact I started having night sweats, I tested at 6.5 weeks (46 days) after the incident at a Point of Care with an INSTI HIV-1/HIV-2 needle prick test. The test was negative. Should I count the results of the test be conclusive? I have not had sex with anyone since that incident. I think most likely that the sweating was due to severe anxiety because after the test the sweating stopped dramatically. Also, I have read that no tests that have been negative with contemporary hiv antibody tests like the INSTI have come back to be positive after 3 months. Is this true? I have read your post about why the 3 month rule is popular for liability reasons etc. My immune system is in good shape and I dont get sick very often.

Also, I read that a new strain of hiv was identified in November of 2019, but that it is a subtype of the common hiv1 type and that very few people have it. My question is would this strain show up on an INSTI test and is that something I would need to be concerned about?

Thank you for your expertise

66 months ago

my fault what I meant to say is I have read that no tests that have been negative with contemporary hiv antibody tests like the INSTI have come back to be positive after 3 months. Is this true? Also I have read a study (the ncbi.nlm.nih.gov one) that ssays the INSTI hiv1/hiv2 test is 99% accurate at day 57. does that mean that it is conclusive at 46 days with the same test?

Thanks again

H. Hunter Handsfield, MD

66 months ago

Welcome to the forum. Thanks for your question.

HIV is quite rare in sexually active women in the UK, including sex workers. Add that statistic to your partner's apparently truthful belief she isn't infected, and you can take it to the bank: it is exceedingly unlikely she has it. And even if she has HIV, the average risk of HIV transmission for a single episode of unprotected vaginal sex (if the female is infected) is around 1 in 2,500. Taken together, your risk of HIV from this single exposure is well under 1 in a million.

And there is no such thing as a negative HIV antigen-antibody (AgAb, 4th generation) test 6 weeks or more after acquiring HIV: that test result is conclusive. The negative result makes your symptoms irrelevant, i.e. proves your night sweats or any other symptoms are not possibly caused by HIV. To my knowlege, there are no HIV types that do not give positive results with INSTI.

Your follow-up statement is correct. In fact, I believe there have been no failures of the test to detect infection at 6 weeks; no need to wait 3 months. Per regulations of the US FDA and its counterparts in most countries, the manufacturer's data on test performance must take into account people who turn out to have special circumstances. My guess is that anyone whose positive result was delayed more than 6 weeks had taken anti-HIV drugs, delaying test positivity; or did not accurately know which of several exposures was the acctual source of his or her infection.

All things considered, there is no chance you have HIV. It was an overreaction to be avoiding sex on this account. I hope these comments help reduce your fears and resume a rewarding sexual and romantic life. Let me know if anything isn't clear.

HHH, MD

---

66 months ago

Hello Dr. Handsfield thank you for your insightful and assuring reply!

A follow up question I have is this,

In your reply you stated "there is no such thing as a negative HIV antigen-antibody (AgAb, 4th generation) test 6 weeks or more after acquiring HIV: that test result is conclusive."

I mentioned that the test I took was an INSTI HIV-1/HIV-2 test at 6 weeks and not an HIV antigen-antibody (AgAb, 4th generation). I have read that the INSTI test is considered a 3rd generation antibody test and not a 4th generation antigen test. If this is the case, would the 6 week INSTI HIV-1/HIV-2 test still be considered conclusive even when it doesnt check for antigens?

H. Hunter Handsfield, MD

66 months ago

You're right: my bad -- sorry. INSTI is third generation. It's an excellent test and almost always positive by 6 weeks. But it can take up to 8 weeks, which is consistent with the data you cite about reliability at 7 weeks (57 days).

But even if you consider your result "only" 98-99% certain, you should consider it conclusive. Let's do a little math. Odds your partner had untreated HIV (despite her assurance), let's say 1 in a thousand (it's probably lower). Chance you were infected if she had it, 1 in 2,500 (0.04%). For the odds your test missed your infection at 6 weeks, let's estimate 5% (it's probably lower than that). Given all this, the chance you have HIV is 0.001 x 0.0004 x 0.05 = 0.0000002. That's 1 in 5 million. I hope you would agree that's zero for all practical purposes. And because the numbers above are probably too high, your actual risk is lower still.

If you'll feel better having a negative result at a truly conclusive time, ffeel free to get tested again at 8+ weeks. But I certainly wouldn't do it if I were in your situation. (I wouldn't have been tested at all!)

---

66 months ago

Thank you for your clarity and assurance

I have no other questions

H. Hunter Handsfield, MD

66 months ago

Thanks for the thanks. That's why we're here. Take care and stay safe.---