HIV testing at 10 days

[scott2000]

Hi, Doctor-
I swallowed semen 10 days ago and I would like to take an HIV test.  I've since learned that the person with whom I did this is VERY promiscuous in the gay community and occassionaly does this for pay. Amidst the sea of information and misinformation out there, the best I can find is that a p24 antigen test is appropriate and accurate at this juncture.  Does this test cary a risk of false negatives?  Could you please clarify the controversy surrounding this test.  THANK YOU!  

[H. Hunter Handsfield, M.D.]

I'm an unaware of any "controversy surrounding" p24 antigen tests.  However, a PCR test would be even better than p24 antigen.  The PCR has a higher risk of false positvies, but also might be more effective in detecting early infection.  However, this is outside my immediate expertise; I'm not sure either test is wise or necessary at this point, since the risk of catching HIV in this situation is low, although not zero.  But neither you nor I should be deciding exactly what tests to have.  See a health care provider who is familiar with HIV/AIDS, explain the situation, then follow his or her advice about what tests to have and when.

Now comes the lecture:  It was a mistake to have sex of any kind with such a high risk partner without first discussing HIV, i.e. telling him your HIV status and asking about his; and avoiding sex with those who are positive, don't know, or are evasive about it.  In the long run, "Do ask, do tell" is just as important in HIV prevention for men who have sex with men as are condoms for anal sex.  And think how much less worried you would be if he had said he is HIV negative and seemed to be honest about it.

Good luck--  HHH, MD

[scott2000]

Thank you, Doctor, for your advice and frankness.  This was my first foray into my bisexual desires, and I have learned A LOT about safety in the wake of it all.  I hope others read my post and your response.

If I might get a little clarification, I know some people (non-experts in the community forum) dislike the PCR and p24 test because of false positives, but are there also false negatives?  In a funny way, I'm more willing to accept a false positive and do follow up testing, since my paranoia already has me expecting the worst.  It;'s the false negative that seems more damaging to me.

Thanks for your time and the good work you do!

[H. Hunter Handsfield, M.D.]

As you apparently are aware, it takes time for any test for HIV to become positive.  The tests that directly detect the virus (tests for p24 antigen or PCR to detect HIV DNA/RNA) start to become positive a few days after exposure and are positive in most infected people by 2-3 weeks.  The antibody tests start to become positive at 10-14 days and are almost always positive by 6 weeks, rarely longer.

Before those intervals, all these tests can be falsely negative.  But after ~2 weeks for p24 and PCR and 4-6 weeks for antibody, false negative results are rare.

Persons at risk for HIV are generally wiser to plan on routine HIV testing at intervals, rather than getting tested after every potentially risky event.  The average gay/bi man in the US probably should just test once a year -- or if at particularly high risk (e.g., men who often have unprotected anal sex), as often as every 3 months.  Of course there are exceptions for especially high risk exposures, e.g. if someone has had anal sex with a known-infected partner.

[Weed84]

I don't know if I should post this and or you would answer it but , since you talked about testing at 6 weeks is always good and rarely they give out false negative.

Isn't Rapid Testing More Accurate ?

Have you ever seen someone go from Negative at 6 weeks to positive at 13 weeks ?

hope you answer, if not, I understand.

Thank you

Wee

[H. Hunter Handsfield, M.D.]

"you talked about testing at 6 weeks is always good and rarely they give out false negative."  True.

"Isn't Rapid Testing More Accurate?"  No.  Rapid testing has a higher chance of false positive results than laboratory-based antibody testing.

"Have you ever seen someone go from Negative at 6 weeks to positive at 13 weeks?"  No, and with the modern HIV tests in use for the past decade, I have never heard of such a case from my colleagues.

That will have to end this thread.