Does PEP affect the antibody window period?
Sep 7, 1999
If you had an occupational exposure to HIV and took PEP would this affect your confidence in a negative antibody test after six months? I've read on other forums that there is a possibility that PEP would delay the onset of antibody production. But if you took PEP for the one month and it didn't work, I'm guessing that after six months you would still most likely have antibodies. Would you agree or do you think people in this situation should test further out and/or take another kind of test as well?
Response from Mr. Sowadsky
Thank you for your question.
At this point in time, we simply do not know if going on Post-Exposure Prophylaxis (PEP) after an occupational exposure to HIV, will affect the HIV antibody window period or not. There have been some cases where a healthcare worker had an occupational exposure to HIV, went on PEP therapy, but they became infected anyway (in other words, the PEP therapy did not work). Although PEP does prevent infection with most occupational exposures (when it is properly used), in some cases, we know that PEP has failed, and the exposed individual became infected anyway. In very rare instances, it has been reported that in some people where PEP had failed, they took longer than the usual 6 months to test positive on an antibody test. This may have been due to several reasons:
1) The person was one of those extremely rare individuals (less than 1%) who took longer than 6 months to show positive on the antobody test, OR
2) In extremely rare instances, the healthcare worker was simultaneously infected with hepatitis C during their exposure. It has been suggested (but not proven) that perhaps co-infection with hepatitis C affected the window period, OR
3) PEP may have had some affect on the window period.
Because documented PEP failures are rare (after a proven occupational exposure to HIV), and because seroconversions beyond 6 months are also rare (less than 1% of cases), it is difficult to know if PEP had an effect on the window period, or if these rare seroconversions beyond 6 months were simply an unusual (chance) event.
As a general suggestion, if a healthcare worker had a documented exposure to HIV, and if they went on PEP, they may wish to continue HIV antibody testing up to a year after the exposure (rather than the customary 6 months). An exposed worker may also want to continue testing up to a year if they were simultaneously exposed to hepatitis C (or another bloodborne disease) at the same time. They may also want to take a qualitative PCR test under these unusual circumstances. However, if a healthcare worker had an exposure, but they did not go on PEP, and/or they were not exposed to any other bloodborne disease, then testing up to the customary 6 months is all that would usually be necessary.
In summary, presently, we simply do not know if PEP would affect the HIV window period or not. Remember, we are talking about an extremely rare situation here. But we can say that PEP, and/or co-infection with another bloodborne disease, may theoretically affect the HIV window period. But until more information becomes available, we cannot say if PEP would have any proven affect on the HIV window period or not.
If you have any further questions, please feel free to e-mail me at "firstname.lastname@example.org" or call me at (Nationwide). I'm glad to help!
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