[Question #2891] HIV exam

40 months ago
Hello Docs,
Last month I had one negligible risk for hiv, I've performed and received anilingus from a CSW.
At that time, I had a injury in my gum from brushing my teeth. I only used my tongue, trying to make the affected area clear.
I did the Hiv p24 antigen exam / AB 32 days later, and the result came out negative. I know that is a good result, but the result
itself was 0.00. I did this exam many times and I am not sure about this results, because it's the first time that I see 0.00.
would you please coment this? thank you
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
40 months ago
Welcome back to the forum.

There are no specific data on the risk of HIV transmission from anal-oral contact (analingus), but there have been no reported cases of HIV being caught or transmitted by it, so the risk probably is extremely low. This also fits with the fact that HIV rarely is acquired by any oral exposure (even swallowing infected blood or semen almost never transmits HIV). And there probably is similar low risk for receiving analingus, partly because the virus is not carried in saliva and not likely to be present on the tongue of an infected person. Further, as discussed in your thread a few months ago, few CSWs in North America have HIV -- typically one chance in 100 to 1000. So the odds are strong your prtner wasn't infected.

Finally, your test results are conclusive. There is no difference between results that are below the usual cut-off for positive results, generally around 0.9. In fact, the same blood specimen tested 10 times will give 10 different numbers. In other words, there is no difference between, say, 0.00, 0.2, 0.5, or 0.88. All are equally and completely negative.

It takes up to 6 weeks for the Ag/Ab tests to become positive, so in that sense your test was a bit early. However, probably 98% would be positive by 32 days, so combined with the virtually zero risk from the exposure itself, you can be 100% confident you did not catch HIV.

I hope this information is helpful. Let me know if anything isn't clear.