I have seen lot of question about HIV DUO Test. It is very unfortunate nobody recommenging for HIV DUO Test. But all are recommending HIV Anitibody (Elisa) test at 3 months mark.
I have no partnership at medhelp, but being a medical professional, I will like to discuss the question raised by the gentlemen previously in this forum. The studies compare the early diagnosis of HIV by 3rd generation and 4th generation HIV tests which has proven to be better by 4th generation ELISA. The studies can NOT compare the ability of 3rd generation ELISA in detecting P24 antigen with 4th generation ELISA, as 3rd generation checks ONLY for antibodies and NOT for P24 antigen at all.
90 days is the usual safety window period for HIV antibodies test (which checks ONLY for antibodies and NOT for P24 antigen). This is the main difference between 3rd generation ELISA tests (also rapid HIV tests such as INSTI which check for antibodies only) and DUO tests, as DUO HIV tests check for both antibodies and P24 antigen.
P24 antigen is usually detectable by 28 days, the time when antibodies may still be not detectable. So DUO will check for both antibodies and P24 Antigen and hence will help in possible earlier diagnosis of HIV at the time when antigen will be detectable, but not the antibodies. Once the antibodies start producing, P24 antigen will usually start disappearing and again as DUO will also check for antibodies so it will also be again helpful that time. That is why it is also called Sandwich test.
Rarely, the DUO test may be false negative in the circumstances when P24 antigen becomes undetectable but antibodies still not detectable, but ofcourse it would be a RARE finding. In short, DUO is a 4th generation ELISA and its effectiveness in detecting the antibodies is the same as that of 3rd generation ELISA tests and reliable approved rapid HIV tests, however its capability to detect early infection is due to its capability to detect P24 antigen which is usually high in early infection and then declines, once the antibodies become greater. Antibodies will then be detectable for the rest of life, except in EXCEPTIONALLY RARE circumstances.
If you are still worried, you may repeat the HIV antibodies only test after 12 weeks or 90 day. At that stage antibodies in most infected persons would be already detectable and hence no doubt will remain in your mind.
I am sorry to explain all this but I do not feel there would be any study comparing the detection of P24 antigen by 3rd generation HIV tests and 4th generation HIV tests, as 3rd generation tests DO NOT check for P24 antigen at all. However studies have focused on difference of time between the two tests in detecting HIV infection, which from all this discussion is clear that will be most likely quicker by a 4th Generation ELISA (such as a DUO test).
In my personal opinion HIV DUO Test is a reliable test before the window period.
The British HIV Association; the British Association for Sexual Health and HIV and the British Infection Society have published new testing guidelines for HIV in the UK.
The consensus advice recommends the use of an HIV DUO test (4th generation combination antibody and p24 antigen) as a first line test because it has the advantage of reducing the window period to one month (28 days).
If a DUO test does not detect HIV in 28 days it does not rule out that anyone may still be infected. Early detection does not have anything to do with a conclusive negative test. The guidelines to HIV test is still 3 months.
Yes. I agree with you. To confirm, a test is at 3 months is good. But a HIV DUO test is better than a HIV Antibody Test at three months. All doctors, medical professenels, HIV Experters are recommending for HIV DUO
The antigen portion of the DUO test is only good up to 3 weeks after infection. When the antibody production begins the antigens are no longer detectable and there may not be enough antibodies produced at that time to be detected by the antibody portion of the test.
Please please we need o update the knowledge in regard to P24 Antigen.
1. It does not disappear just like that. Once antibobies are produced the P24 antigen remain TOGETHER with the antobodies ... for up to 2 months and even longer.
2. DUO/Combi tests are designed to detect both or individual parts of the test.
3. The DUO/Combi test covers ANY lag or cross over period between P24 being present and the creation on Antibodies.
4, In March 2010 The British HIV Association; the British Association for Sexual Health and HIV and the British Infection Society have published new testing guidelines for HIV in the UK. 28 day negative results are conclusive. But if clarification is required by the idividual then a 12 week test should be offered.
I thought I should add the new BASHH guidelines, for the exact wording
As you will see the wording "conslusive" is not mentioned, and its replaced with "definitively exclude".
BASHH Statement on HIV window period
15 March 2010
HIV testing using the latest (4th generation) tests are recommended in the BHIVA / BASHH / BIS UK guidelines for HIV testing (2008). These assays test for HIV antibodies and p24 antigen simultaneously. They will detect the great majority of individuals who have been infected with HIV at one month (4 weeks) after specific exposure.
Patients attending for HIV testing who identify a specific risk occurring more that 4 weeks previously, should not be made to wait 3 months (12 weeks) before HIV testing. They should be offered a 4th generation laboratory HIV test and advised that a negative result at 4 weeks post exposure is very reassuring/highly likely to exclude HIV infection. An additional HIV test should be offered to all persons at 3 months (12 weeks) to definitively exclude HIV infection. Patients at lower risk may opt to wait until 3 months to avoid the need for HIV testing twice.
Dr Keith Radcliffe Dr Simon Edwards
Chair, Clinical Effectiveness Group Chair, BASHH HIV Special Interest Group
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.
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