[Question #5200] Oral sex and hiv duo testing parameters

22 months ago
Hello Doctors. Just ending this saga and had a couple of more questions. I saw of a couple of days ago  Dr Hook's response that 99% duo tests are conclusive at 28 days. My issue was unprotected hetero oral sex only both ways. I, for piece of mind, had a duo test at 26 days. I am thinking that  26  days would be the same as 28 as far as the 99% number goes. I have experienced no fever, no rash, but have had a sore throat for 2 weeks. I take it that if this sore throat was due to ARS, that I would have tested positive with my 26 day duo because a duo test would always be positive with seroconversion in process.  Do you with my percentages and conclusion?
Also, I was curious how a duo test would not be conclusive at 26 days due to the supposed high of p24 antigen at that time, as well as the increase in antibody if seroconversion had in fact occurred as the p24 antigen decreased. Seems like it would be difficult for the test not to pick up p24 and/or antibodies at the 26 day mark if infection had occurred.  If it is to complicated to explain, I get it. Just thought I would ask. Seems to make sense but I  am not a scientist.
Again thanks for the services you provide. 

H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
22 months ago
Welcome back, but I'm sorry you find it necessary. You really ought to disregard the times to reliable testing. Just have a 100% conclusive test at a sufficient time after the last possible exposure, the stop worrying. Examples of such times are:  6 weeks after a lab-based antigen-antibody (duo, 4th generation) test; 8-10 weeks after a third generation antibody test; or 4 weeks after a combination of PCR (i.e. RNA testing) at 2+ weeks plus AgAb or 3rd gen antibody test at 4 weeks. Since your previous thread was 3 weeks ago, it seems likely that one or more of these interval have passed.

I agree there probably is no measurable difference in reliability between 26 and 28 days for an AgAb (duo) test. Why isn't that test 100% conclusive at ~4 weeks? You're exactly right that it should be, in theory. However, human beings and their physiology and immune systems are complex systems, and some people apparently are outliers. There is no specific reason, or none known, that on rare occasions it takes a bit longer.

Finally, you need to stop focusing only on the test for evidence you didn't  catch HIV. Your exposure was about 4 weeks ago. Let's go through some numbers. If your partner was at average risk for HIV, the chance she had HIV probably was no higher than 1 chance in a thousand she had HIV. If a sex worker, maybe up to 1% chance, no higher. Chance of transmission:  let's use CDC's figure of 1 chance in 20,000 for mouth to penile transmission. (There have been no cases known by cunnilingus, so we can ignore it. Or if you like, use the same figure as for fellatio). Next, let's say your current test results are 99% reliable, i.e. 1% chance you are infected and the test missed it. With these figures, the odds you have HIV can be calculated as 0.001 x 0.00005 x 0.01 = 0.0000000005. If I've correctly counted the decimal places, that's 1 chance in 2 billion. In other words, zero.

Thanks for the thanks. I hope this settles things for you. If it doesn't, have another duo test once you pass the 6 week mark. If you do that, you of course can expect a negative result. There's no chance you have HIV.

HHH, MD
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22 months ago
Dr. HHH,
Thanks for your reply. Yes I agree. The long term  sore throat was what prompted me to ask. It has lasted since Day 15 to the present which is day 34. But as I have read, if this sore throat was actually caused by an HIV  infection, then the test on duo test on Day 26 would have been positive since I would have been officially seroconverting. Clearly with no fever, no rash ever, and a negative duo test, I am not, right?  Thanks for your help. Take care...………..
22 months ago
40 vs 42 days for final duo an issue? Thanks and please close out the thread. I really appreciate your advice.