HIV Prevention and Testing > Am I Infected?

false positive p24?


Hi,  My husband got an occupational exposure of infected sputum from a tracheostomy to his eye and began anti viral meds right away as well as the first and the 6 week test.  On the 6 week test everything came out non-reactive except for the p24 antigene.

We can't get the specific results now (the level of p24) or the level of the p24 in the previous test because the dr. is not around until Tuesday.

My question is, is it at all possible to get a reactive p24 and NOT have HIV?  I know that there is no waay to tell me he doesn't have HIV right now, but I would just like to rest a bit this weekend witth knowing that there is hope.

Thanks so much,  this sputum by the way, was no ordinary sputum.  It did not have visible blood in it but, the guy was bleeding from his trach the day before, so it must have surely had some blood particles in it.  And my husbands eye was bloodshot from the first day of his wearing contacts.

From the lessons here at

--- Quote ---P24 Antigen Test: This test uses ELISA technology to look directly for key pieces of the HIV virus the p24 protein found on HIV's outer coat. This test can reduce the chance of a false-negative in standard (antibody) ELISA testing is done too early (i.e., less than 13 weeks after exposure). The p24 antigen test may be ordered if there's been a very recent risky exposure to HIV, such as a healthcare work-related incident. Blood banks also use it for screening donations.
Valuable in detecting HIV infection early in the window period after exposure, this test is only useful for a period of approximately three weeks after exposure, before the production of antibodies begins. A p24 test result should be confirmed by antibody testing once the window period has passed.

--- End quote ---

It would appear that a P24 test is not recommended after three weeks. What that means in terms of your husband is likely good news, especially since no other markers were reactive.

Thanks, I just needed a little hope in getting through this weekend!  I appreciate you being there.  And I read that quote from the testing page (someone reads the moderators remarks), but it didn't quite touch on the possiblity of falibility of p24 reactivity.

Andy Velez:
Just want to say those other non-reactives are definitely encouraging. I can believe that you and your husband are grateful for any good news. I would say the odds are well in his favor against transmission having occured.

Best of luck and please keep us posted.


Thanks guys, much appreciated.  I will let you know what happens.  Take good care and be well.


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