Expert: Terry B - 12/19/2008

Question
hi terry, i have researched some sites providing info on HIV. but i ask you since you are an expert. is P24 antigen test result reliable at 3 weeks post exposure?

some sites say 2-3 weeks, some say 3-4 weeks, while others say 11-14 days!.i am not in a hurry but i also cannot wait 3 months for ELISA. so please tell me can i have P24 antigen test at 3 weeks?

some also mention that once antibodies start developing p 24 antigen would not give true picture.

also i have had RNA PCR(polymerase chain reaction 27 days after potential "exposure") with a negative result. can i consider it to be "definitive"?

also would it be wise to have P24 antigen test at 3 weeks or  have a [P24 antigen test + HIV tridot test] at 4 weeks post exposure?

i would be grateful to you if you can answer my multiple questions. thank you

Answer
Dear Karan:

Peace.  

Understand that my expertise in HIV is broader than you would find in asking a laboratory expert; I depend on their opinions (spoken and published) rather than performing the lab tests myself.  Based on what I have heard and understand, both P24 antigen and PCR testing should, if HIV is present, be reactive as soon as 72 hours post-infection.  The risk of these tests is primarily in the false positives and the costs.  

Why not wait until six weeks from exposure and add results from an ELISA to the data you have?  At six weeks, an ELISA is fairly reliable indicator if you have antibody, and combined with your other test results, might move you toward the 'definitive' place you are seeking.  

Another question on why you "can't wait" - what do you need to do differently?  Is there a sudden demand for you to expose others to your fluids?  If you are being responsible in your sexual behaviors (I assume you're not talking about donating blood or tissue) you are protecting yourself and others by means of abstaining, being monogamous with a monogamous partner, or using latex barrier protection.  That need not change while you await further testing.

Best to you and yours,

Terry