[Question #14013] Testing accuracy at 45 days while on PrEP
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1 months ago
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Hello again,
Just over 45 days ago, I had unprotected insertive anal sex (I was the top) and rimmed a transgender woman. She indicated she was on PrEP as well and tested every three months, but never know for sure. I got really sick several days after this. Fever, sore throat, muscle cramps, chills, blood in stool. I believe it was the rimming that caused this, maybe a bacterial infection, but don’t know for certain. First time this has happened to me. Really shook me up. It eventually cleared and I just did a panel of STD tests at 45 days. Everything has come back negative thus far. Believe they’re still working on the chlamydia and gonorrhea. I’m curious as I’m on PrEP, is 45 days from exposure conclusive for a fourth gen HIV Ab/p24 Ag with Reflex test? I’ve seen conflicting information online that PEP/PrEP can delay the true result and to retest at three months. Is this true? I wish I would have known this and asked before this.
Thank you
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H. Hunter Handsfield, MD
1 months ago
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Welcome back. However, since you have chosen to pursue the most risky of all sexual lifestyles in regard to HIV -- unprotected anal with other men (i.e. anatomically male, if transgender) with frequent new partners, you should be in regular care with a knowledgeable HIV prevention expert doctor or clinic -- presumably the prescriber of your PrEP. I'm of course happy you're on PrEP and encourage you to continue it. But as for the HIV testing schedule, you should be following your doctor or clinic's advice. If you're in the US, most likely they follow the standard CDC guidance, which is that PrEP users should be tested every 3 months with an AgAb (4th generation) test; optionally an HIV RNA PCR test also may be done and probably is routine in most cases. There is no need to stop PrEP for such testing: if PrEP fails, it will be because of exposure to an HIV strain resistant to your PrEP drug(s) and therefore testing will be reliably positive.
In other words, discuss with your doctor(s) and follow their advice. Our forum is not a substitute for direct professional care in that manner.
In addition, with this lifestyle you also should be on doxy-PEP, i.e. doxycycline 200 mg single dose following individual high risk exposures. This reliably prevents syphilis and chlamydia and reduces the chance of gonorrhea by about 50%. (In theory, there is less need for doxy-PEP following condom protected exposures, but many or most prevention experts still advise it.
As for your recent illness, I agree it almost certainly was a non-STI gastrointestinal infection; and also agree that rimming was the likely route of exposure. Given blood in you stool, there's a good chance you had shigellosis (bacterial dysentery), salmonella, or other similar infection. Perhaps tests for these are in the works, although usually such tests take only 2-3 days for result to be available. Neither chlamydia nor gonorrhea was likely; presumably those test results already are known to be negative.
I hope these comments are helpful. Let me know if anything isn't clear.
HHH, MD
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1 months ago
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Hello,
This person indicated it had been awhile since they had been with someone. I am in the care of a clinic, yes. I got these tests on my own because I thought from reading, 45 days was conclusive for HIV with a fourth gen test, just wanted closure. But then I saw if you’re on PrEP it can complicate that. Is this the case? As far as the clinic, I test every three months, yes. I am doxy yes, I always take it if I have an encounter like this. No, I never tested for the bacterial infection, I should have or at least asked about it when I went to urgent care in the beginning. Seems like it’s cleared up for the most part now though.
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H. Hunter Handsfield, MD
1 months ago
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I'm glad you're getting expert care in relation to HIV prevention: good show! It is likely your clinic and/or your personal provider there are equally knowledgeable about all these issues as we are. While we appreciate your confidence in our perspectives, an expert provider who know you and personally understands your situation remains the best option.
The performance of PEP and PrEP in preventing HIV appears to be excellent, but exceptions can occur. To my knowledge, it remains an open question whether taking anti-HIV drugs, either as PEP or PrEP, might on rare occasions suppress detection of a new HIV infection. The best information indeed is that negative AgAb test results are conclusively reliable after 45 days (often rounded off to 6 weeks). But even if you sometimes test for HIV on your own, it still seems most reasonable to discuss it with the provider who knows you best.
Also good to hear you're on doxy-PEP. But although highly effective in preventing syphilis and chlamydia, it isn't perfect by any means and is definitely not reliable against gonorrhea. Therefore most clinics and providers would agree that doxy-PEP users should be tested periodically for all three of these STIs. The actual frequency of testing -- e.g. every 3, 6 or 12 months -- probably should be based on the frequency of potentially risky exposures.
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1 months ago
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Yes, I’ve been going to the clinic for several years now. They have a heavy focus on STD prevention. All right. I’ll ask my prevention specialist. I just thought y’all were more knowledgeable about PrEP, how it works, and the statistics.
I’m pretty adherent to my PrEP program. I may rarely miss a dose now and again, but that’s it. So the test I took IS conclusively reliable at 45 days is what you’re saying? If the antibodies are suppressed by PrEP, wouldn’t the antigen still show up? Okay, again I’ll ask my prevention specialist tomorrow. She gave me a finger prick test early on, but to my understanding, that test is too early, takes longer for a conclusive result, which was my reasoning for testing on my own with a fourth gen. Yeah, they test me every three months for the other STDs as well, which I like.
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H. Hunter Handsfield, MD
1 months ago
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That's not how anti HIV drugs work. There is no such thing as treatment suppressing antibodies while antigen persists. The drugs prevent growth of the virus itself, which means antigen; antibody can develop only if antigen appears first.
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If the chance of HIV infection is very low say one in 10,000 and a test is done that misses 1% of infections (like a finger stick test might do), then the chance someone has HIV after the negative result is one chance in 100 million. Which is zero for all practical purposes. You can continue to rely on your personal HIV provider!
That completes the two follow-up comments and replies included with each question and so ends this thread. I hope the discussion has been helpful. Best wishes and stay safe.