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elisa etst @ 14 weeks after PEP

Sep 22, 2005

Dear Dr. Frascino,

I hope it is OK to address this to you directly? I have read your various responses on elisa test windows.The grey area seems to be with regards to the 13 week window if you take PEP.

I recently had a pontential sexual exposure to a HIV, in East Africa.( broken condom)Within 20 hours I was placed on PEP, a tripple regime, for a month. .8 days after potential exposure a blood sample was sent for a PCR test, which came back undectectable, (less then 400.)18 days after potential exposure an intracellular DNA PCR test was done, and the result was negative. I was assured that these should be sufficient to exclude HIV transmission to me.However I did also have a Elissa test as well as a rapid test 14 weeks after the date of potential transmission, which are negative. There is confusing advice on when to end the testing.May i ask why I read elsewhere that after PEP we should test for 6 months, and yet some sites suggests that count 6 weeks from end of PEP, ( I.E 10 weeks) You state as follows:THis is from PATHCARE south africa. "Most HIV ELISA tests become positive 3 weeks after exposure and all HIV ELISA tests should be positive 6 weeks after exposure." ( it's the "should" that has me worrying of course)

"In cases where the healthcare worker has taken prophylaxis, the time before tests are performed should be calculated from the day the prophylaxis was stopped."

Much research also suggests that all PCR / DNA PCR tests should only be conducted after PEP is concluded, as it can suppress viral load results, if they are present.The explanation I was offerred is that if there was an acute infection, and PEP was not effective, even this therapy could not completely suppress the intitial burst of viremia completely, and there vwould be some indication of viral load in the initial stages. Further more the negative Intracellular DNA PCR ( after 18 days) was proof of no virus was present in Plasma.

I am no virologist, but very ready to listen and learn, if you have the time to reply.

I hope that this is not an intrusion, however I am most apreciative of any explanations and advice that you can offer,as I have much faith in you.


Response from Dr. Frascino


Hmmm . . . . You're wondering if it's O.K. to call my Dr. Frascino??? Now there's a switch. Most folks worry about calling me Dr. Bob!

The specific answer to your question is rather complex and beyond the scope of this forum. However, you can read about it in the published guidelines "Antiretroviral Postexposure Prophylaxis After Sexual, Injection-Drug Use, or Other Nonoccupational Exposure to HIV in the United States." Recommendations from the U.S. Department of Health and Human Services Published in MMWR January 21, 2005 / 54(RR02);1-20 which can be downloaded at (

The bottom line is that PCR testing is not recommended during PEP, because antiretroviral drugs could suppress an HIV viral load to an undetectable level, thereby giving a false negative result. HIV-antibody testing (ELISA) for those who have had an HIV exposure significant enough to warrant PEP is recommended at baseline, 6 weeks, 3 months and 6 months after exposure. I agree with these recommendations/guidelines.

Hope that helps!

Dr. Bob

I've asked you this question for over 3 years w/no response...
My partner & his partners are HIV positive. I'm negative, how come?

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