[Question #3217] STD/HIV

37 months ago
Had a one night stand (unprotected vaginal, I was the insertive partner) back in September 30th. October 5th (5 days after exposure) had a whole std panel done everything was negative. October 11th (11 days after exposure) I had a HIV RNA qualitative test (aptima genprobe), it was negative as well. October 26th (26 days after exposure) I had a fourth generation test done and it was negative. Then November 8th (39 days after exposure) I had another fourth generation test done and that too was negative.

I know the CDC just recently changed their guidelines to 42 days. My questions are:
1) Is the 39 day test conclusive?
2) If no, supplemented with the HIV rna test would that make it conclusive?
3) Would the chlamydia and gonorrhea test at 5 days be conclusive?
4) Should I move on or have another std panel done?

H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
37 months ago
Welcome to the forum. Thanks for your question.

First, I'll point out you had a low risk exposure. In the US and most industrialized countries, few women -- including the most sexually active, including sex workers -- on average fewer than 1 in a thousand have HIV. And if a woman has HIV, the average transmission risk during a single episode of unprotected vaginal sex averages once for ever 2,500 exposures. These figures predict that there was less than one in a million chance you caught HIV. If you then were tested with an assay that detects "only" 98% of infections (e.g. your 4th generation test at 26 days), with that result the odds you had HIV dropped to 1 in 50 million. Perhaps you'll agree that's zero for all practical purposes! (Still, in the future I hope you'll get into the condom habit for similar events!)

In other words, following most potentially risky exposures, it really doesn't take 100% test reliabilty to prove someone doesn't have HIV. If somehow I had been in your situation, I would not have had the RNA test at 11 days and would have stopped testing entirely after the 26 day Ag/Ab test.

But now to your specific questions:  The CDC advice, and the scientific reviews that lead to it, are based on the assumption that only one type of test is done. Combinations of tests, using different technologies, are more reliable soone.Your questions themselves imply you already understand this.

1) The 39 day test probably was 100% conclusive. There is no statistical difference between 39 days and 42 days (6 weeks).

2) Yes, the combination of negative RNA plus the other test results after that amount to 100% conclusive results.

3) Assuming you had a urine test, the results are conclusive by 5 days.

4) I would not recommend any further testing, except that you don't mention syphilis. A negative blood test at 5 days is meaningless (except to show you didn't have syphilis before the exposure). If you haven't had another syphilis blood test, I would recommend it now. You can expect it to be negative -- syphilis is almost as rare as HIV in this situaiton.

So it's definitely time to move on without further worry. I hope these comments help you do so. But let me know if anything isn't clear.