[Question #7911] STD and HIV Questions

50 months ago

Hello Doctors.

First off, I want to thank all of you for the wonderful work that you do. The advice you have given has been incredibly helpful and a tremendous resource. The local resources in Hong Kong, where I live, haven’t been updated in years and follow old protocols (i.e. the testing at 3 months rule).

In April I was at my GP for a checkup and I did my annual STD and HIV blood test (all vein drawn and performed in a lab). My results sheet says the tests were for HBs Antigen, VDRL and HIV I/ II Ab & P24 Ag – all negative. Where my recent anxiety lies is that after recently breaking up with my ex-girlfriend, it dawned on me we never discussed STD status and testing. We never had sex (no oral, no vaginal etc.) but engaged in deep kissing, dry humping in underwear and mutual masturbation.

My questions:

· Am I correct in saying that the HIV I/ II Ab & P24 Ag is the 4^th gen test? Different labs refer to it differently (combo/ duo etc.) so I want to make sure

· Is it true that dry humping in underwear, mutual masturbation and kissing are not risks for spreading HIV? My last exposure was 80 days (dry humping and mutual masturbation) and 39 days (kissing) before taking the HIV and STD tests. Are my negative results conclusive or is further testing needed?

· Per the advice given to others on this forum, I have read that the 4^th gen test is highly reliable and does not produce false positives after 6 weeks (unless PEP/ PREP is involved) – is that because it tests for antibodies AND antigens? Are antibody only (2^nd and 3^rd gen) tests as reliable after 8 weeks?

· In a response to another user, I read that a negative 4^th gen test is conclusive at 6 weeks no matter the level of risk of the exposure (i.e. sharing needles vs. kissing). Am I interpreting that correctly?

Thank you again.

H. Hunter Handsfield, MD

50 months ago

Welcome back to the forum. I reviewed your recent discussion with Dr. Hook and agree with all he said. The short answer this time is that you definitely do not have HIV and can stop worrying about it. You were never at risk, not in the slightest. To your specific questions:

Correct that the antigen-antibody (AgAb) test is the updated terminology for 4th generation, duo, combo.

HIV cannot be transmitted through clothing, or by any sexual activity that does not include direct genital-genital or genital-rectal contact, almost always requiring penile penetration. As Dr. Hook said, even oral sex is zero risk or close to it, with no known transmission events oral to penis, and only rare ones in the other direction. Kissing is not known to transmit the virus either. (Saliva kills HIV, and swallowing HIV infected fluids, including blood, is low risk.)

Correct on all counts. The HIV AgAb tests are among the most accurate diagnostic tests ever developed, for any medical condition, and the results overrule all other factors. No matter how high the transmission risk at the time of exposure, and no matter how typical of a new HIV infection symptoms might seem to be, the test result rules. And yes, that is largely because of the combination of both antigen and antibody testing, but the current standalone antibody tests (3rd generation) are equally conclusive after 8 weeks.

Correct. Test performance is independent of the exposure risk. However, at times we have advised questioners in a way that on first glance can seem to say otherwise. Let's say someone is tested early, e.g. at 4 weeks, when the AgAb test detects 99% of infections. If it was a low risk exposure, i.e. the chance they caught HIV is maybe only 1 in a million, we would advise that even though the test itself isn't quite conclusive, like most scenarios on this forum, the negative result at 4 weeks reduces the likelihood of HIV to 1 in 100 million, which is zero for all practical pruposes. But if someone had, say, unprotected receptive anal sex (bottom) with a known infected partner, the prior probability of infection would be 1 in 200 before testing and 1 chance in 20,000 with a negative test at 4 weeks. That's a very low risk, but too high to consider conclusive. For that person, we would recommend another test at 6+ weeks.

You should not give HIV another thought at this point. Stop testing and do your best to stop worrying!

Best wishes. Let me know if anything isn't clear.

HHH, MD

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50 months ago

Thank you, Dr. Handsfield. Your advice and confidence in my latest test has been reassuring.

I probably should have mentioned this in my inquiry but in case it matters, the previous question answered by Dr. Hook (which he definitively answered and put me at ease) and the one that you have just responded to are two separate incidents. Admittedly the previous encounter with the CSW left lingering guilt which has led to increased anxiety and caution with my ex, hence this thread. In any case, the explanation of context does not appear to have any bearing on your answers.

I noticed a typo in my 3^rd question and meant to say, “false negative” NOT “false positive”. I recall in an earlier forum discussion you said the fear of a false negative with regards to a 4^th gen test should be negligible because it tests for antibodies and antigens, is that correct?

Lastly, appreciate your explanation regarding exposure risk and the timing of the 4^th gen test. Am I right to say that in instances with the highest level of risk (say the receptive anal partner in your example), a single test at the 42 day mark would be conclusive? Apologies if this is redundant but I want to make sure I understand the principles.

H. Hunter Handsfield, MD

50 months ago

If I understand correctly, you new sexual contact was zero risk (kissing only, clothing on, mutual masturbation) -- beyond that I didn't see any need to consider whethere it was the same or a new contact and partner.

Thanks for the clarification, but for sure you need not worry about false negative AgAb test results 8 weeks after the last possible exposure. And yes, 42 days is always conclusive regardless of the nature of the exposure.

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50 months ago

Thank you very much, Dr. Handfield. You have addressed my immediate concerns.

In my final follow-up, I would like to ask more general questions while I have the chance:

1. Are there any concerns about false negative results after the 6+ week mark with AbAg tests (assuming no PEP/ PREP)? Both you and Dr. Hook have absolute 100 % confidence in the 4^th gen test after 42-days even with higher risk activities (sharing needles, receptive anal sex with a known HIV positive male etc.) and I wanted to understand why and check if there was anything else to say to those (like myself) who have lingering concerns (beyond “seek counseling” anyway). I have noticed neither of you have advocated for further tests under even high-risk exposures beyond a single test on or after 42-days

2. Apart from the oraquick fluid test (which you have said are your least favorite tests), were accuracy and false negatives more of a concern for antibody only tests vs. AbAg tests? I have noticed this was a point of discussion in other websites, favoring the latter as it tested for two markers instead of just one

3. Is there a difference in reliability and accuracy between vein drawn lab tests compared to instant tests (apart from oraquick fluid tests)? Where I am, they are used by several HIV organizations despite little regulation

4. Are there any important developments in the areas of HIV vaccines or cures?

If these general questions belong in a separate thread, please let me know. I apologize if some are repetitive – my OCD wants to better understand the details as much as a “layman” can as I make changes for the better.

Lastly, in case I don’t get to before this thread closes, I want to genuinely thank you once again for your expertise, time and patience in answering my questions and the many more like it from others. It is much appreciated.

50 months ago

Hello Dr. Handsfield,

As a footnote to the first question from my third follow-up, I came across this response from question #7001 eleven months ago where you said, "there is no such thing as a false negative results more than 6 weeks after catching HIV" when another user made a similar inquiry about AbAg tests.

Thanks.

H. Hunter Handsfield, MD

50 months ago

Your comment indicates you understand that opporunities for follow-up comments are intended for clarification of the initial quesiton, not to raise new issues. Hence succinct replies:

1. Confidence in the AgAb tests is based on solid knowledge of the time course of Ag and Ab in blood, the science behind the tests to detect them, and absence of credible reports of tests missing infection after ~6 weeks.

2. The amount of antibody in crevicular fluid (from the gum line) is 100 fold lower than in blood, raising the chance of false negative results. The standalone blood antibody tests are 100% conclusive after 6 weeks, i.e. 2 weeks longer than the AgAb tests.

3. Most experts consider the lab-based tests slightly more reliable, although any difference is small.

4. Nothing new recently in progress toward and HIV vaccine or cure.

I stand by the statement you quote from a previous thread.

Please note that the fourm is designed primiarily for evaluation of particular exposure events, symptoms, treatment, etc. For general questions about HIV and other STIs, I would suggest other kinds of research. There are plenty of online sources for more comprehensive discussion than practical on this or any online forum. But I do hope your two disucssions have been helpful. Best wishes and stay safe.

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