[Question #3190] Specifically for Dr. Hunter Handsfield regarding 4th gen elisa

39 months ago
This question is specifically for Dr. Hunter Handsfield:
Based on your statement, 28+ days after a risky exposure the negative result of 4th generation elisa duo lab test is 100% conclusive. 
I tested two 4th gen. ag/ab lab tests (Roche and Abbott's Architect both FDA approved) 29 days and 33 days after a risky exposure. Both came back negative and I was relieved BUT today (day 34), I faced with the seroconversion panel: Donor#75062, Panel code: HIV9079 , Zeptometrix corporation (you can google it). The individual was diagnosed HIV+ with 4th gen. Combo Abbott only 40 days after exposure. The rusults were False negative before that. How do you explain this?
I appreciate you comments and feedback.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
39 months ago
Welcome to the forum and thanks for your question. I logged in a few minutes after you posted it:  most users should not expect nearly real-time replies! FYI, it is only by chance that I'm answering and not Dr. Hook. As stated in the forum instructions and FAQs, users do not select the moderators who respond.

First, 28 days indeed was long thought to be the cut-off time for conclusive results for the Ag/Ab ("4th generation") HIV blood tests, but a few months ago a scholarly publication* reviewed the existing data and concluded that although 98-99% of newly infected people have positive results by 28 days, 6 weeks is recommended for 100% conclusive results, and that is the advice we have been giving on this forum the last 3-4 months.

Hence, I "explain" the patient you refer to by conclusing he was just one of the unlucky few in whom it can take up to 6 weeks. (It seems possible that this particular seroconversion panel participant is one of the cases that led to the modified conclusion about 6 weeks versus 4 weeks for conclusive testing.) I have no way of knowing whether there were any other extenuating factors, such as the possibility that that person took any anti-HIV drugs as post exposure prophylaxis (PEP) after the exposure event.

If you would like to say more about your own risky exposure, I could help interpret your results at 29 and 33 days. If it was relatively low risk, then those results probably should be considered conclusive. But if the risk was truly high, such as unprotected vaginal or anal sex with a known infected partner, you should have another test after 6 weeks.

* https://www.ncbi.nlm.nih.gov/pubmed/29140890

I hope this information is helpful. Let me know if anything isn't clear.

HHH, MD

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39 months ago
First, I would like to thank you Dr. Handsfield for your prompt and accurate reply.

I had unprotected vaginal sex with a girl. At my request she tested a 3rd generation antibody test 10 days after exposure with "negative" result. However, I can not find out her sexual activities over the last three months or so. Based on this piece of information how do you evaluate my case? Logically and scientifically should I test again in 9 days ?
39 months ago
I should also add that I am 44, white, circumcised. She is 23 white. None of us have any other STDs and hepatitis. Both of us tested for them.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
39 months ago
Assuming you're in the US, the chance any particular 23 year old woman has HIV is very low, probably under 1 chance in a thousand; and with her negative test, you can be even more certain she isn't infected. You don't need to know about her sexual exposures in the last 3 months:  it isn't your business and you shouldn't ask, even if you could. So I would consider this a zero risk exposure and would have recommended against you being tested for HIV. However, you can consider your current results conclusive and I don't recommend any further testing for HIV.

With unprotected sex, of course your risk of other STDs, like gonorrhea and chlamydia, was a lot higher; and there was slight risk of syphilis as well. You should have a urine test for gonorrhea and chlamydia, if not yet done, and a syphilis blood test, which will be conclusive at 6 weeks.

And you probably don't need to be told this -- but you should get in the condom habit in the event of similar events in the future!

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39 months ago
I confess that it was a thoughtless and passionate behavior! I am very careful about using condoms and this was an exception. I will reschedule for those STD tests that you mentioned.
The thing is that she lives in Iran (that I guess) with an unknown solid HIV statistics. I have this feeling that she is a business-girl that can be hooked up with rich or older man. Do you still recommend no extra testing in 9 days and my results so far conclusive? I appericate your final recommendation.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
39 months ago
I'm glad to hear non-condom use was an exception.

In absence of easily available data, I imagine that an upscale escort in Iran, who hooks up with "rich or older men" (probably a low risk group in itself!) knows how to protect herself, finds ways to be tested, and is low risk to have HIV or bacterial STD. Of course in absence of any way to know, I would understand if you decide to have another test. Many people in similar situations are more reassured by negative testing than by probability and statistics, even from very expert sources. Anyway, it's up to you.

Safe travels!
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39 months ago
I appreciate your great help and advice.
39 months ago
Dr. Tan, a famous expert with many clinics in Singapore believes that a later than 28 day HIV positive diagnosis with fourth generation elisa duo test is solely because the patient was under PEP or Chemotherapy or he/she was co-infected with hepatitis C or his/her body has an obvious immunodeficiency problem or he/she is a rare sero-negative person among population.  Otherwise, he firmly believes that a negative 28 day negative result "only" with 4th generation combo lab test can never ever turn back positive. Do you agree with him ?
Have you seen personallly in your long practice a negative result (wih a 4th gen. Duo test) in day 28  turn to positive after 28 days ? 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
38 months ago
Well, the recently published scientific review begs to differ (https://www.ncbi.nlm.nih.gov/pubmed/29140890), and that paper was accompanied by an editorial from CDC, agreeting with the conclusions and recommendations. It could be Dr. Tan is correct that this simply cannot happen without some sort of extenuating circumstance, and that's what we said on this forum for several years. But that's not what the data show -- unless there were such circumstances in some of the patients analyzed, and I would think persons known to have such circumstances (especially PEP) would have been excluded. But in any case it's a minor issue if 1-2% of newly infected people take a bit longer to develop positive tests. 

No, I have not seen this among my patients. But that's irrelevant. Rare things happen. I've also never cared for a patient struck by lightning.

That concludes the two follow-up comments included with each question and so ends this thread. Take care and stay safe!

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