Risk assessment, testing advice - protected sex with CSW

[pitas]

Hi. 29 days ago I had an encounter that's probably nothing to worry about but I'd appreciate your expert advice. I'll cut to the chase. I'm male. Had protected sex with a female sex worker. Latex condom was used correctly as far as I could tell (it was on the entire time, didn't slip off, didn't split, was covering the top of penis). The duration of this was quite short, too. I was a bit worried so I went to see my doctor. Similar to what I've read you say in other posts, my MD said to not worry about HIV in this case. He did tell me that I could test if I wanted to but he didn't see a need. I decided I would do a rapid test and got one at the drugstore and did it at home (Oraquick oral swab). On day 29 this test was negative.

1. Is my MD's risk assessment and advice reliable? He's not an expert on STDs and HIV like you are.
2. Is this 29 day negative with Oraquick rapid oral test good enough? (I know from reading on here all about window periods, etc.)
3. Would you suggest any further testing?

Thanks in advance for your help.

[H. Hunter Handsfield, M.D.]

Welcome to the forum.  Thanks for your question, and for reading other threads with questions similar to yours.

Your doctor is exactly right, both in his risk assessment and testing advice. In the US, generally fewer than 1% of female CSWs have HIV, and mostly it's even lower chance, perhaps 1 in 1,000.  When the woman is infected, there is an average of one chance in 1,000 to 2,000 of transmission by a single episode of vaginal sex.  So even without a condom, that works out to an average transmission risk around 1 in a million.  Adding a properly used, intact condom to the calculations, the chance you caught HIV is zero for all practical purposes.  To your specific questions:

1) I agree exactly with your doctor.

2) The oral fluids test is the least reliable for early HIV testing; it takes longer than the blood tests to become positive following a new HIV infection, and in general I don't recommend it unless at least 3 months have passed since the last possible exposure.  In contract, the blood tests -- both rapid and lab-based -- are virtually 100% reliable at 6-8 weeks.  Still, your negative results at 4 weeks is probably 75-80% reliable.

3) From a medical or risk standpoint, no additional testing is necessary (no testing was necessary at all).  But if you need to have a 100% reliable result for reassurance purposes, you'll need to have a blood test in a couple of weeks, or another oral fluids test at 3+ months.

In the meantime, if you have a regular partner, you can safely continue unprotected sex without risk, without additional testing.  That's what I would do if somehow I were in your situation.

I hope this has helped ease your concerns.  Best wishes--  HHH, MD

[pitas]

Again, thank you Dr. Handsfield. You've given me a lot of reassurance.

[H. Hunter Handsfield, M.D.]

1) Exactly right -- that's a nice summary of my reply above.

2) This would be little more than guesswork, but maybe ~90% at 6-8 weeks.  I won't try to speculate beyond that.

[pitas]

Thank you Dr. Handsfield. This is helpful. A couple of questions:

1. You mentioned transmission and prevalence probabilities. Do these even matter when a latex condom is used correctly? I mean, whatever the product of these probabilities is (which is an infection probability conditional on no condom protection) shouldn't matter because wouldn't this then be multiplied by zero because of a condom? Or at least a very small number?

2. I'm curious to read your remark about the oral fluid rapid test being less reliable. Just out of interest (and for others who invariably will read this thread), what do you think the reliability is for an oral rapid test at five, six, seven, eight weeks? You said 75-80% at four weeks.

Thanks. I'm going to not worry about further testing given, as you put it, this was effectively a zero risk situation and even a 75% reliable negative test result at four weeks is reassuring enough for me.