[Question #11819] HIV testing window
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12 months ago
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Hi I am curious about contradictory information from traditionally reliable sources on HIV testing. A recent (2023) article on NIH states “ Patients with possible exposure need repeated testing during the 4 to 6 months following exposure”.
Later in the article it says most will react 3 weeks with 4th gen but some may take 3 months, if past 3 months the test is read as a true negative. How do I make sense of this contradiction? Also, why does the cdc still recommend 6 month testing after a needle stick? I believe your answers and the science behind the 4th gen window but I’m confused by how many reputable sources still use a 6 month timeframe or contradictory information.
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H. Hunter Handsfield, MD
12 months ago
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Welcome to the forum. Thank you for your confidence in our services.
It would be helpful to know more about the 2003 "NIH" article. Can you provide a more detailed citation or perhaps a link?
There are many varied personal opinions about timing of HIV testing after a high risk exposure; some physicians have different standards or opinions than others. However, the scientific evidence is clear: there have been few if any HIV infections in which the antigen-antibody (AgAb, 4th generation) blood tests did not become positive with 45 days. The only known exception is if someone has taken anti-HIV drugs, e.g. as post-exposure prophylaxis (PEP) which doesn't work. After PEP the testing window typically is 4-6 weeks after the last dose of drug.
CDC is the main public health/prevention resource in the US, and its positions are considered conclusive. NIH is a fine institution of course, but its main role is research, not day-to-day prevention standards. But in any case, an article from someone at NIH doesn't necessarily represent an official NIH position. As for 6 months, I've never heard of any knowledgeable, reputable agency advising that the AgAb tests take that long for positive results. That's not to say that some individual physicians might not have such advice. But there absolutely is no scientific basis for it.
I hope this information is helpful. Let me know if I can help further; or if you can provide more information about the NIH article you found.
HHH, MD
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12 months ago
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https://www.ncbi.nlm.nih.gov/books/NBK482145/
I wasn’t sure if links were allowed initially but here is that link. Article is from last year and seems to have contradictory information or I am just not understanding it well. If possible let me know what you think and I may use my last response for a more personalized question regarding my situation if you are able to get back to me
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H. Hunter Handsfield, MD
12 months ago
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Thanks for the citation. It's an article in StatPearls (www.statpearls.com). I'm not highly familiar but it's an online for-profit textbook (sort of) that recruits and pays authors to write essays on clinical advice and opinions. Almost all medical literature is collated by the National Library of Medicine, which is part of NIH. That includes StatPearls, but the articles, advice, and opinions have nothing to do with NIH. The authors of this article are not recognized HIV experts that I recognize and in searching the medical literature I find no significant HIV clinical or research track record for either of them. One of them has published 15 StatPearls articles; the one cited is the only one about HIV.
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As for their specific advice, they do not cite particular references for their 6 month testing recommendation. One (charitable) interpretation is that most people at significant risk of HIV or other STDs remain at risk as time passes. Therefore, repeat testing is usually advised. As worded, it's conceivable that their 6 month advice only refers to the desirability of continuing to test people at high risk at frequent intervals. But the bottom line is that I would advise both health professionals and individuals concerned about HIV testing to ignore the article entirely.
Feel free to go ahead with your personal question. But if it concerns AgAb (4th gen) HIV testing after a potential exposure, you might be able to predict my response.
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12 months ago
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Yes, thank you so much for checking out that article and clarifying it for me. I understand the firm consensus about the window for Ag/Ab. I suppose I will just close by confirming that in your experience, regardless of test, the window period maximum is 12 weeks and often earlier for 4th gen and RNA.
I’m sorry for being repetitive it is just nice to hear from experts that the 6 month window is no longer relevant because it still gets quoted a lot by free-lance writers for health pages like WebMD, the article aforementioned, and other pages which resemble legit sources.
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H. Hunter Handsfield, MD
12 months ago
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The window period max is 45 days (which we often round off to 6 weeks) for the AgAb (4th gen) tests; and 11-12 days for PCR/RNA.
Advice for a 6 month window ended 15-20 years ago, once the world moved on the original (first and second generation) HIV blood tests. There are plenty of hyper-conservative doctors that still advise 3-6 months, but there is no scientific evidence for this. There has never been a reliably reported case of the AgAb tests taking more than 45 days, not counting people who took anti-HIV drugs for PEP that didn't work.
That completes the two follow-up exchanges included with each question and so ends this thread. I hope the discussion has been helpful. Best wishes and stay safe.
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