P24 Antigen

Hi Everyone

I have been finding some conflicting information concerning the p24 antigen and Duo Tests.  I am wondering if the p24 antigen stays at detectable levels past 6 weeks.  Some people seem to be saying that after 6 weeks the p24 antigen is no longer at detectable levels and thus becomes useless as a diagnostic test for HIV infection at this point and only an antibody test will work past 6 weeks.

Anyone know??

[Teak]

P24 has a very short window period. Once antibodies to HIV are formed they attach to the P24 antigen and makes them undetectable.

[IBelieveInGod]

Dear Teak,
This means that at that stage the antibodies MUST be detectable. so when the antibodies attach to the P24 they will be detectable in the test.

[xxxjason]

So if seroconversion were to be delayed, the p24 antigen will stay detectable untill antibodies were produced no matter how long this takes?

[xxxjason]

Can someone answer this?

[LIZZIE LOU]

"so if serocenversion were to be delayed"

IT'S NOT ! !

you have 52 posts/comments on this forum regarding a NO RISK situation.

time to move on.

[rubberball314]

Please if those who know about this treatment should take note of the info below.

HIV 1 and 2 antibodies and p24 antigen test (HIV DUO or HIV Combi test)

This HIV test is licensed in the EU for use after 28 days after a possible exposure. It is probably much better than this and will probably identify the majority of newly infected HIV positive individuals at between 14 and 21 days. This HIV test is referred to as a fourth generation HIV test. Certainly in our clinic we have had many new diagnoses of patients using this HIV DUO test combination in that time frame.

The HIV DUO test relies on the principle that when HIV first establishes itself in the body it will start to replicate rapidly and almost as a by-product of this replication a core protein - the HIV p24 antigen - is produced in huge amounts from around 10 days or so after first infection and before or during the time when antibodies to HIV are being formed. The p24 antigen will then stay at a very high level for the first few months after infection and later decline in line with the decline in HIV viral load as referred to above. It will though never completely disappear and will run a variable course of detection through the rest of the illness.

So in general, p24 antigen is formed slightly before antibodies are forming allowing us to close the gap between infection to detection time - the HIV window period. As time goes on, then the majority of newly infected HIV positive people will form antibodies to HIV 1 or 2 by 28 days. In combination then, looking for both the HIV 1 p24 antigen and also HIV 1 and 2 antibodies will allow for much earlier detection of HIV than looking for HIV antibodies alone.

In the UK at 28 days the result is 99.98% accurate..... not 3 months as some say....

The test time is 28 day ONWARDS the p24 does not become undetectable it remains in at high values for up to two months post infection.

Test is a combination so the antibodies will be picked up at the later stage of the infection developement.

The UK is soon to reduce the window period for this test as it is so accurate.

So please those who keep on saying your not clear until 3 months you are out of date in regard to 4th generation tests.

[Teak]

http://www.fda.gov/downloads/BiologicsBloodVaccines/BloodBloodProducts/ApprovedProducts/LicensedProductsBLAs/BloodDonorScreening/InfectiousDisease/UCM216314.pdf

Page 27
Current methods for the detection of HIV may not detect all infected individuals. An ARCHITECT HIV Ag/Ab Combo test result that is nonreactive does not exclude the possibility of exposure to or infection with HIV-1 and/or HIV-2. Nonreactive results in this assay for individuals with prior exposure to HIV-1 and/or HIV-2 may be due to antigen and antibody levels below the limit of detection of this assay.


UK testing guidelines.
Post-test discussion

The need for a repeat HIV test if still within the window period after a specific exposure should be discussed. Although fourth generation tests shorten the time from exposure to seroconversion a repeat test at three months is still recommended to definitively exclude HIV infection.

http://www.bhiva.org/documents/Guidelines/Testing/GlinesHIVTest08.pdf

[jessemy]

Hi,
You say 28 days would be conclusive. would it make much difference if the test was done at 27 or 26 days?
I had a possible exposure and can be seen at the clinic this week (which would be 26 days after) or next week which would be 33 days.

Id rather have it done sooner than be waiting stressing for a week and was wondering if having it done at 26 days would be conclusive or i should definitly wait till next week.

Hope this'l get a reply as its quite an old thread.

Thanks

[Viky818]

3 months (90 days) will be conclusive

[ahmedfaris]

I have done HIV 1&2 AB and p24 AG after 23 days of exposure the result was negative shall I consider it conclusive or I have to repeat it I am so confused I think you'll be giving me the right info