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p24 test result please clarify

Jul 21, 2006


first, I wanted to say that you are doing a tremendous job here helping people. I have posted twice but did not receive any reply. Hope you will reply this time.

I had an encounter with a sex worked in Bangladesh recently. The fisrt was June 10th and I used a condom. The second one was July 1st, used a condom but when I pulled out found the condom is inside her. I was seeing symptoms everywhere since then.

On July 10th (I was back to North America) I took a p24 test. I Got the result back today, it's negative.

I know FDA does not approve p24 for diagnosis, but how accurate is this test for these two encounters? From the dates...the test has been done 30 days after first incident and 10 days after second exposure. Does usually HIV virus show up in blood to be detected in p24 test after 10 days of exposure? is the p24 test too late for the first encounter (well in the first one I used condom without any I think I should not worry about that one)

Thanks in advance.

Response from Dr. Frascino


The p24 antigen test, due to its lower cost, is sometimes used as an alternative to HIV RNA PCR test to detect acute HIV infection. However, it is not completely reliable. If the test is positive, the individual is HIV positive (100% specificity). However, the sensitivity of this test is not nearly as good. The test fails to detect up to 25% of people who are infected with HIV.

You are back in the U.S. now. My recommendation is to get an HIV-antibody test (ELISA or equivalent) three months or more after your last possible exposure. Stop worrying about symptoms. They are unreliable in differentiating pozitoids from negatoids!

Good luck!

Dr. Bob

Clueless in Chicago
PCR DNA Tests and Funny

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