I would like to have your advice about the accuracy and window period for the Hiv 4th generation test. Some advices says it’s conclusive after 6 weeks and never need to repeat them again after. But some says it’s conclusive by 3 months ! And some says it’s recommended to repeat the test 6 months for conclusive and more accurate result ! I didn’t know what is the right one.

1- My main concern is about the 6 months window period , i did the hiv 4th generation test after 3 months and the result negative , some mentioning that 6 month is old and out of date recommendations! I didn’t understand what that means out of data .and should i repeat the test by 6 months for a conclusive result or that was never needed to repeat a test after 6 months with the 4th generation test ? Like form your experience and knowledge for conclusive and accurate result should I repeat the test after 6 months?

2- after 3 months i did 4th generation test and hiv pcr Genexpert , both negative result. can a combination of these tow tests a negative pcr test with negative 4th gen test change by 6 months ?

You're right -- there is great variability in advice on timing to conclusively negative HIV test results. False positive results are rare, so a positive result is always reliable regardless of the time since exposure. That can be as soon as couple of weeks after being infected, So this question really is pertinent only to time to a reliably negative result. My comments are limited to the HIV antigen-antibody (AgAb, "4th generation", "duo") tests. HIV providers and public health experts no longer recommend the "generation" terminology.

First, you can limit the variability (at least online) to a large extent by sticking with scientifically oriented resources, i.e. professional sites like academic medical centers and public health agencies. Especially avoid sites run by and for infected people or those at risk, without medical/scientific moderators.

Second, the variability even from scientific and professional sources often reflects simple lack of keeping up with the latest science; procrastination in changing advice as science evolves; but sometimes there a social, behavioral, or religious intent to discourage sexual behavior for example.

On this site, we rely on the US Centers for Disease Control and Prevention (CDC), which has published advice that 45 days is sufficient, no need to wait longer for conclusively negative results. CDC in turn bases its recommendations on an authoritative review published a few years ago; you can track it down at https://pubmed.ncbi.nlm.nih.gov/29140890/. We usually round that off to 6 weeks, i.e. 42 days, because it's a round number easy to remember and there have been no scientifically reliable reports of anyone being negative at 42 days and positive at 45. Three or even six month advice is left over from earlier antibody-only tests, rarely if ever used anymore. Even then -- with the earliest HIV tests e.g. in the early 1990s -- it rarely took longer than 4-6 weeks. No scientifically knowledgeable source has ever recommended 6 months for the AgAb tests, and even 3 month advice has always been uncommon.

Combination testing is conclusive sooner. For example, nobody with a negative HIV PCR test at 2 weeks plus negative AgAb at 4 weeks has ever been reported to have a positive result later.

There is one exception to the 6 week or 45 day advice for the AgAb tests:  when the exposed person takes anti-HIV drugs as pre- or post-exposure prophylaxis (PrEP, PEP), the window is extended to 6 weeks after the last dose of drug, and some experts advise as long as 3 months.

So you were unnecessarily over tested. Your negative AgAb test at 3 months was conclusive, and is confirmed by the negative PCR result; you need no more testing at 6 months or any other time. There is no possibility you have HIV and should not waste any more time, money, or emotional energy on HIV testing.

I hope these comments are helpful. Let me know if anything isn't clear.

HHH, MD

By saying “ No scientifically knowledgeable source has ever recommended 6 months for the AgAb tests, and even 3 month advice has always been uncommon.”

I would like to have your opinion on an exposure type if it can transfer hiv or not.

Thank you Doctor for all

Wish the best for you

That completes the two follow-up exchanges included with each question and so ends this thread. Best wishes and stay safe.