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Unprotected Oral Sex, Elisa Combo and PCR


Hi all
first of all I've to say this helpline is very useful and well done too.
Let's move straighforward to the point. I'm in a homosexual relationship since 3 years but in May we decided both to have one experience each with other guys, always protected insertive sex and both did unprotected oral sex without ejaculation in the mouth and without any sort of contact with blood.
Doing some math
My Boyfriend took an Elisa 4th generation (antibodies + p24) test 35 days after the "possible" exposure with the unprotected oral sex he had, results negative (no reactive).
I took a PCR RNA test after 15 days from the last exposure combined with a Elisa 4th generation test resulting "undetectable , less then 37 copies/ml " and not reactive to the antibody + p24 test.

I know PCR RNA is not a diagnosing tool (but my doctor prescribed me because he found me very anxious) because of high cost, technical problem and high rate of false positive but that actually is a high sensitivity test (so very few false negative results). What I am wondering now is
1) does my boyfriend can take his results as conclusive ?
2) can i take mine as conclusive ?

Now we are 6 (my boyfriend) and 4 (me) weeks after the last possible exposure and we do not have any syntomphs.
Thanks for all !


Hi there, and thanks a lot for contacting the AIDS Vancouver Helpline for your HIV/AIDS related health information. It seems you're concerned about the possibility of HIV transmitting during an encounter, and about the accuracy of some tests you've had. We're happy to answer your question for you.

Protected sex is considered a low risk activity, and unprotected oral sex is also considered a low risk activity. Low risk means that while transmissions are possible, they require specific circumstances to occur (like the condom breaking during sex, for example). Consider these risk levels in your decision to go for testing after these specific situations.

Here is a bit more information on the tests you mentioned:

Test Name
Window Period
4th Generation EIA Blood test that looks for antibodies AND p24 protein antigens. Commonly referred to as the "combination," "combo" or "DUO" test. P24 protein is detectable immediately after infection but only for the first few weeks. The antibody (ab) test has a window period of 4-12 weeks post exposure. This test is widely available in North America. Most HIV specialists consider this test to be conclusive at 6 weeks but official HIV testing guidelines still recommend re-testing at 12 weeks for conclusive results. Conclusive at 3 months post exposure.
Pooled RNA NAAT or “Early Test” Detects viral RNA in blood of people who have yet to develop detectable antibody levels. 10-12 days post exposure The pooled RNA test is often expensive and not readily available. One must be referred by a health care professional to receive this test. An antibody follow up test after 12 weeks is sometimes necessary depending on how long after the exposure the test was performed. Conclusive at 3 months post exposure.

You'll see in the chart that both tests are considered conclusive at 3 months post exposure. So if you wanted to know your status conclusively after these encounters, you'd need to wait at least 3 months before testing. Tests at 15 and 35 days are too soon to demonstrate your present status conclusively.

Thanks a lot for contacting the AIDS Vancouver Helpline with your question, we hope it has been answered fully.


AIDS Vancouver Helpline/Online