[Question #4908] PRep or Pep exposure and reliability of test

27 months ago
Hello Dr.’s,

I have read much and it’s my understanding that a 4th generation duo test is 100% conclusive and reliable at 6 weeks. It’s my understanding that nothing can interfere with these results of being reliable and conclusive at 6 weeks with a 4th gen duo test. 

The one item I have read that can lengthen that 6th week testing reliability on the 4th gen duo test, is for those who are taking PrEp or Pep. I am not on either of these and do not need to be. 

My question becomes, can continual exposure to PrEp or PEP among those who are on it such as utilizing same bathrooms, hospital settings, potential residue on surfaces who are taking these medications, affect those who are not on it in regard to the reliability of a 6th week duo test being reliable? Or, potentially, limited exposure to these medications among those who are on them, yet I myself am not taking them, affect testing reliability. Can being exposed to PrEp or PEP, but not taking these medications personally affect the reliability of a 6th week duo test?

I have read that 2nd hand chemo is possible among caregivers from utilizing same toilets, etc. Which raised the question to me, can exposure to PrEp or Pep do the same whereby affecting the testing reliability of a 6 week 4th gen duo test?

My results are indeed non reactive from 4th gen duo tests at 6 weeks and longer. Truly, no risk either, just hyper vigilant.  I just have this lingering question on potential exposure to PrEp or PEP, but not taking it myself, therefore I can indeed trust my non reactive 4th gen duo test results at 6 weeks and longer since I am not taking it myself?

H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
27 months ago
Welcome to the forum. Thanks for your confidence in our services, and for reading other questions pertinent to yours. Also for an interesting, insightful question.

In essence you are asking if, with so many persons taking anti HIV drugs for PEP or PrEP, other persons might be sufficiently exposed to those drugs -- through sex or perhaps shared toilets or other contaminated environments -- to affect reliability of HIV test results, or the time for tests to become positive if exposed and infected. 

My belief is that this is exceedingly unlikely; it hs difficult for me to believe that the amounts of anti-HIV drugs that might be absorbed from such exposure would be far too small to have any such effect. That said, I am an STD/HIV clinician, epidemiologist, and prevention specialist -- but not a virologist witih in depth knowledge of these issues. I'll check with a couple of colleagues who have such expertise, and will let you know within a few days if they have contrary opinions. But in the meantime, I don't think you need alter your sexual exposures or plans for HIV testing on account of this issue -- that is, that you can indeed trust your negative AgAb (4th gen, duo) test results 6 weeks after your last potential exposure.

I hope this information is helpful. I'll post a follow-up comment soon.

HHH, MD

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27 months ago
Thank you much for your insight. That is helpful to know your opinion. I look forward to your further reply once you check with colleagues on my question.

Thank you.
27 months ago
Just one added component to my above question I just thought of to add; might drinking water that that has discarded pharmaceuticals in it such as PrEP or PEP  affect one’s 4th gen 6th week duo reliability? I’ve recently read that  pharmaceuticals can end up in water plants potentially making its way to our faucets. Or,  bodies of water one may swim in whereby discarded or excreted medications could appear where one may swim.  Likewise, potential unclean water drinking outlets such as frequented potable water consumption on aircraft too or other potentially unclean water drinking outlets.  Is there any chance, this component of having PrEP or PEP in it, may have an affect on reliability of testing reliability at 6 weeks? This all seems unlikely, but a worthy question to inquire of.

It would also seem that if any if this were possible, from my initially posed question in relation to this topic and this question in relation, the affirmation of a 6th week duo test being 100% conclusive would not have that high of a reliable rating I would believe. Something would be known by now, if any of this had affect on reliability of testing?

It would appear, I agree, that if one is not on PrEP or PEP, but has any exposure to it, that it would be too limited to have any such affect in your opinion. Yet, defined clarity on this is so appreciated.  I appreciate you checking with your colleagues on my question regarding this topic with this added question which is in relation to my above question on having continual or limited exposure to PreP or PEP via different indirect aveneus, but not taking it myself, thereby not affecting the reliability of my 6th week and longer 4th gen tests. Thank you for your time and I look forward to your response as you check with your colleagues.

Thank you.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
27 months ago
I checked with a couple of HIV virology experts. Both agree that the amount of drug to which one might be exposed would be far too low to have any protective effect if exposed to HIV, or to have any effect on time to conclusive testing if such a person acquired HIV.

There indeed are environmental, ecological, and potential personal health consequences of drugs and medications of all kinds entering ground water and other environmental niches, and I suppose it could someday be an important issue for anti-HIV drugs. But I and my colleagues are unaware of any studies so far, and are not concerned this is having any effect on HIV transmission, induction of drug resistance in HIV, or HIV testing standards and policies. I really don't think you need be concerned.

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27 months ago
That's very good to know, thank you! I can rest assured now that my negative 4th gen tests at 6 weeks and longer are indeed 100% conclusive and reliable. Thank you much for your expert knowledge/insight and for the expert answer from that of your colleagues, much appreciated. Thank you!
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
27 months ago
Thanks for the thanks. I'm glad to have helped. That concludes this thread. Best wishes and stay safe.---