[Question #9391] HIV Fase Negative and False Positive
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33 months ago
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Hi Doctor,
I had an exposure in early September and have tested for HIV using 4th generation test at 14 days, 28 days, 46 days and 65 days. All tests are NEGATIVE. I'm starting to trust the results but my doctor is very adamant on a 90 day test. Given I'm still 3 weeks away from 90 days, I'm starting to worry about false negative and false positive HIV tests.
1. What are the conditions that can cause false negative 4th generation lab tests?
2. Will prolonged consumption of garlic supplement, fish oil or strepsil causes false negative or false positive tests?
3. What are the conditions that can cause false positive 4th generation lab tests?
4. Can having a cold / flu cause cross reactive antibodies that cause false positives?
5. Are false positives common with 4th generation tests, or is it more to do with 3rd gen tests and rapid tests?
Thank you
I had an exposure in early September and have tested for HIV using 4th generation test at 14 days, 28 days, 46 days and 65 days. All tests are NEGATIVE. I'm starting to trust the results but my doctor is very adamant on a 90 day test. Given I'm still 3 weeks away from 90 days, I'm starting to worry about false negative and false positive HIV tests.
1. What are the conditions that can cause false negative 4th generation lab tests?
2. Will prolonged consumption of garlic supplement, fish oil or strepsil causes false negative or false positive tests?
3. What are the conditions that can cause false positive 4th generation lab tests?
4. Can having a cold / flu cause cross reactive antibodies that cause false positives?
5. Are false positives common with 4th generation tests, or is it more to do with 3rd gen tests and rapid tests?
Thank you
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H. Hunter Handsfield, MD
33 months ago
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Welcome back to the forum and thanks for your continuing confidence in our services. Having reviewed your recent discussion with Dr. Hook, I agree entirely with his advice, and these questions ask exactly the same ones as before, using different words; or if not specifically addressed, the answers are obvious from that discussion.
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As a general principle, negative results of the standard HIV tests, done sufficiently long after exposure, ALWAYS overrule exposure history and symptoms. No matter how high the risk at the time, and no matter how typical the symptoms seem to be for ARS, the test results rule. All symptoms of HIV more commonly are caused by other things, and absence of symptoms never rule out HIV either. ONLY testing tells the truth: symptoms NEVER indicate HIV in the face of negative tests.
Your doctor is being unnecessarily conservative in recommending testing at 90 days; the tests you had are conclusive any time 45 days or more after exposure.
Those comments answer your specific questions, but to be explicit and avoid any possible misunderstanding:
1, 3. There are no medical conditions, circumstances, or medications that cause either false negative or false positive AgAb (4th generation) tests except that taking anti HIV drugs to prevent infection, i.e. pre- or post-exposure prophylaxis (PrEP, PEP), delays positive test results.
2. None of these causes false negative or positive HIV test results.
4. No effect: see reply to questions 1-3.
5. There are no known causes of false positive results of either the AgAb (4th gen) or current antibody-only (third generation) tests. Rapid tests do so very rarely, which is why positive rapid tests always require confirmation before assuming the result is valid.
Thanks for the thanks. You're welcome. Let me know if anything isn't clear.
HHH, MD
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