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4th Gen Window Period Confusion

It seems a growing number of doctors and experts seem to believe that the 4th generation HIV tests are as good as conclusive at 28 days. However, I find this confusing given that ARS illness can strike anywhere from 2-4 weeks post infection. If, for example, the ARS illness struck at 4 weeks, then would a 4th gen test not be negative at this time. Am I right in thinking that during ARS illness, the 4th gen test would not be able to detect P24 antigen or IgM antibodies? I wonder if my understanding of this is incorrect, because otherwise it seems impossible that any experts could believe a 4th generation test is conclusive at 4 weeks.
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Avatar universal
I'm sure someone else will be able to answer you. Good luck
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Ars typically happens couple weeks after exposure virus is building therefore as p24 is part the virus it can be detected. Later can come seroconversion where antibodies are formed and I'm sure you've read x% by 4 weeks, etc most saying all by 8 weeks like Uk guidelines, some saying 12 weeks. This seroconversion is where a persons blood has antibodies and the p24 starts getting less as antibodies get more. Anything over and above this as a possible answer then I will leave to others
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4 Comments
Thank you for taking the time to answer but I don't think this answers the question.
MH relies on expert doctors who use 28 days so I don't see the reason why anyone getting tested needs to question the physics/biology of the testing process and window period.

I don't ask my clinic to explain how their other tests work as I consider it to be similar to asking the pilot of an airplane that I want to take to explain how every part of the plane works so I can be sure he is an expert.
I completely appreciate what you're saying but i think you'd agree it's a topic of much debate even amongst experts. Hence why I'm sure an expert could provide a quick answer to settle my confusion. It's unfair to tell someone to accept something at face value, when there is a clear reason for confusion. I think everyone has the right to seek a better understanding of a confusing topic.
It's not really a topic that's of that much debate.  If you search around, you'll note that the leading experts in the HIV field consistently state that the 4th generation test is over 99% accurate at 4 weeks.  That is hard to beat for ANY test for any disease.
Avatar universal
Hello from what I understand p24 is in the blood after infecrion with high enough values to be detected by the 4th generation test from about 2 weeks, therefore the recommended test is for 28 days to make sure there is either enoughp24 to be detected or antibodies or both. When antibodies are produced the P24 will decline
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Yes but this doesn't explain the contradiction between the fact that some experts believe the 4th gen test is conclusive at 4 weeks, whilst also maintaining that ARS illness might not even begin until 4 weeks.
You're confused.  ARS and detection of antigens/antibodies aren't necessarily related.  It doesn't matter - antigen formation starts at 2 weeks, while antibody formation ramps up at 4 weeks.  ARS is the body's reaction to the HIV virus replicating.  The 4th gen test isn't looking for the virus itself.  It's looking for antigens AND antibodies, and at least one of the two, if not both, is highly likely to be present and detectable at 28 days.  

You're trying to directly correlate the development of detectable antigens/antibodies with the timing of ARS symptoms.  Some people never get ARS symptoms at all, some get them at 2 weeks, and a small number at 4 weeks.  The test is reliable at 4 weeks regardless.
Thank you Curfew. So is what you are saying that antigens could theoretically be detectable in the blood before ARS symptoms occur. The reason this confused me is because my understanding was that the P24 antigen was the shell of the HIV virus, and therefore the levels of P24 would be correlated to the levels of the virus. And if ARS is caused by the virus replicating, then j didn't think the P24 would become detectable until after the virus had replicated aka after ARS symptoms.

Thank you for answering, it seems from what you are saying that there is no correlation. I can see why it is such a confusing topic.
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