Expert: Kristen Brannock, MPH - 6/17/2009

Question
QUESTION: Hi Doctor!

I had a "risky exposure" 36 days ago.

I was tested both antigen
p24 and antibodies (4º GENERATION ELISA) 12 days after the exposure, and the results were negative.

Then, I was tested again both antigen p24 and antibodies, 20 (almost 3 weeks) days after the exposure, and the results were negative.

Finally, I was tested again both antigen p24 and antibodies HIV (4º generation Elisa) 34 days (almost 5 weeks) after the exposure, and the results were NEGATIVE again.

1. My question is... how much accuracy do these tests I have already made have?
2. Do I need further testing?
3. Do you recomend me a test in 8 weeks or 3 months?
4. I have seen in the forum that a 4th generation test after 28 days is almost conclusive, so my last test would be conclusive?


Please, I would be very grateful if you could answer me, this anxiety is very bad.

Thank you very much, best wishes Doctor.

ANSWER: Enough accuracy that you do not need to test again and can conclude that you are negative- something the testing counselors should have gone over with you.

---------- FOLLOW-UP ----------

QUESTION: Thanks for your answer.

But I have to ask you... Why?

Because, some people say 4 weeks, other 6 weeks ,3 months, and I don't know what to do or what to believe!

I would be very grateful if you could just let me know why.

Thank you very much.

Answer
The best answer I can give you is that the science changes and so does the interpretation. 10 years ago the window period was 3-6 months but scientists realized that that was too long a period and it was more like 1-3 months. I always recommend people to get tested around 3 months post exposure just to be SURE. In all likelihood, their earlier tests were right, but to ease their mind, I suggest a follow up.