[Question #2173] Testing

45 months ago
Drs

I have read many of your posts on here and on another site. You both have advocated that a 4 week (28 day) test using the HIV 4th generation duo test was conclusive.  I met a guy 6 weeks ago and had oral (insertive), mutual mastrbation, and anal sex (insertive partner). I do not know his status.  The condom broke while I was still in him. I freaked out and had to wait 4 weeks for a test. The test was negative. Now I am reading recent posts where you say the 4 week test is NOT conclusive. Why?  Do I need to go get retested now?  I am very scared.  
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
45 months ago
Welcome to the forum. Thanks for your question, which arrived while I was logged in. Most users should not expect nearly real time replies!

We explained in reply to an earlier question a couple of weeks ago that a more recent research review of the current HIV lab tests, including the antigen-antibody tests (4th generation, "duo", "combo"), was published not long ago and came to our attention. Your question gives me another opportunity to address it.

Our previous advice about 4 weeks was based on published results and our (and others') knowledge of these tests and the biology behind them. It remains true that almost everyone with a new HIV infection has a positive result by 4 weeks. However, a very small proportion take slightly longer, up to 6 weeks. So now we are advising 6 weeks as the 100% conclusive interval. Despite this minor change, the vast majority of people can be confident they are free of HIV if tested and negative at 4 weeks.

So I would advise you to have another test at 6 weeks. But it is not appropriate to be "very scared":  almost certainly it also will be negative.

Here are some additional data that should reassure you. The only exposure of the ones you mentioned that carried any risk for HIV was insertive anal sex (which I assume was not condom protected). The current estimate is that if the receptive (anal) partner has HIV, the risk the insertive guy will catch it is about 1 chance in 909 (which I will round up to 1 in a thousand). Let's now assume there's a 10% chance your partner had HIV. So your risk was about 1 in 10,000. Your negative Ag-Ab test at 4 weeks was perhaps 98% reliable, so after that result the chance you have HIV despite that negative result is 1 in 200,000. I trust you will agree that's a trivial chance, close to zero for practical purposes!

So have another test to be certain, but stay mellow in the meantime.

But you have also opened yourself to a lecture:  You had unprotected anal sex with a guy whose HIV status is unknown, presumably meaning you didn't ask him. What were you thinking?? If you keep up that as a regular habit, you should expect to have HIV someday. No guy should ever have anal sex with another man without first discussing mutual HIV status, and avoiding sex entirely (or for sure using a condom) with thoese who are positive (and not on treatment), don't know, or seem evasive about it.

I hope this information has helped. Best wishes and get (and stay) safe!

HHH, MD
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