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  #1  
Old 10-16-2008, 11:25 AM
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Hi, I have read the links on the HIV testing page about the DUO. I have looked at the abstracts for some of the studies, which mostly seem to be about 10 years old. They say the 4th generation test can detect p24 averagely between 4.5 and 8 days or something before a 3rd generation test, which I am guessing is 90 days. Can you explain to me then how they come up with 28 days?
I have tested neg using DUO at 29 days. I need to be sure thats the end of it. Everything is so confusing, such a lot is written about the 3 month window period. Do I need to test in 3 months, or can I now be sure I am HIV negative.
Thanks I know you are busy and have a lot to do.
  #2  
Old 10-16-2008, 11:40 AM
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Hello, there!
The more you go on reading about it, the more you are going to keep worrying! There are thousands of scientific articles published every day and more than once, you can find conflicting information about one specific topic. My advice to you is to stop reading and reading about it and move on.
If you had a negative HIV Duo test of the latest generation (4th) after 28 days of possible exposure, then you don't have HIV and you don't have to have any tests repeated at 3 months. It combines two parameters, the HIV antibodies and the p24 protein of the virus. These can be detected at different points after infection; however the two combined together, if they are not detected after 4 weeks, that means the result is negative and is conclusive. We based this, not just on numerous papers published, but also on many years of clinical experience.
You don't have HIV! Please, forget about it! Move on and be happy!
Best wishes,
Jose
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  #3  
Old 10-16-2008, 05:52 PM
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Default HIV DUO at 28 + days

The dr's wouldn't be allowed to make a false claim about the accuracy of tests. They are governed by the Health Care Commission. It would not only have devastating consequences to give the all clear to someone incorrectly, but morally wrong too. I am sure if the Dr says no more tests are needed, then that should be it, am I right?

Sarah.
  #4  
Old 10-16-2008, 06:21 PM
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Of course, Sarah! Why would we be advising patients not to have a test after 3 months if we were not confident enough in the 28-day HIV Duo test? Apart from not being ethical, it would be stupid as at the end of the day, we are a private clinic and we are a business!
Thank you for your comments.
best wishes,
Jose
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Old 10-16-2008, 07:19 PM
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Hello

I have no partnership at Freedomhealth clinic, but being a medical professional, I will like to discuss the question raised by the gentleman who asked and Dr Jose answered it. 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).

Thanks a lot.
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Old 10-16-2008, 08:26 PM
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Today, after readint this thread, I have googled 4th generation tests, and BHIVA, recognise the DUO as having results available from one month, reducing the window period. Plus I have also seen a new rapid test which will be available later this year that tests both antibodies and antigen, with results in 15 mins- thats got to be good news.
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Old 10-17-2008, 02:21 AM
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Hello Dr Jose,

Your answer specifically related to the HIV duo test results seem very reassuring. I have recently had an INSTI HIV test which came back negative, this was taken after more than 6 months - 1 year of any possible exposure. Would you please also kindly comment on the realiability of this result of the INSTI test? i.e whats the accuracy of this result and if it would be necessary for any further testing? Can i now take this result on board and be rest assured that i do not have HIV and move on? Thanks in advance.

A
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Old 10-17-2008, 11:37 AM
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I have looked at the BHIVA guidelines, like you suggested and it does say that all suspected exposures within the window period be checked with an antibody test in 12 weeks, so you see, the confusion goes on.............................
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Old 10-17-2008, 12:32 PM
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Th Insti test is highly reliable and a negative test after 12 weeks is final and conclusive. You can certainly forget it all and move on.
Regarding the guidelines for cases of HIV exposure, they relate only to the antibody test (like the Insti already mentioned) and not to the HIV Duo. In our experience, someone with a negative HIV Duo test after 4 weeks does not need an antibody test after 12 weeks. However if you are still worried, you can also of course do it.
My advice to you is to try to stop reading and reading in the internet about it; it is not going to help you. It will only increase your worry and anxiety.
Best wishes,
Jose
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Old 02-18-2010, 09:29 AM
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Default Worrying needlessly Dr Sean

Hello,

Golly this one has generated lots of interest.

Going back to your original question


Quote:
Hi, I have read the links on the HIV testing page about the DUO. I have looked at the abstracts for some of the studies, which mostly seem to be about 10 years old. They say the 4th generation test can detect p24 averagely between 4.5 and 8 days or something before a 3rd generation test, which I am guessing is 90 days. Can you explain to me then how they come up with 28 days?
I have tested neg using DUO at 29 days. I need to be sure thats the end of it. Everything is so confusing, such a lot is written about the 3 month window period. Do I need to test in 3 months, or can I now be sure I am HIV negative.
Thanks I know you are busy and have a lot to do.

The problem with all the various information on the subject of HIV testing is that it ages with time. So going back to when I was a newly qualified doctor, we were using 1st generation HIV tests which were a start but very inaccurate and very cumbersome to process. In addition, we weren't for a time entirely sure what we were looking for in the first place. Luckily, laboratories at that time and since had the good sense to store blood.

We've been able as time has gone on to refine the tests and improve them very very much. In addition, because of the stored blood, we've been able to go back and look at the blood samples from thirty years or more ago and subject them to modern testing.

This has established that modern 3rd generation tests will identify over 99% of new HIV positive diagnoses by 6 weeks. Modern third generation tests include the Insti and Dertermine rapid tests.

The HIV DUO is a 4th generation test. This means that it comprises a 3rd generation technology for the antibody part, but also looks for p24 antigen.

The HIV DUO has reduced the time of diagnosis that a third generation test alone will have by around a week or so. The reliability of the HIV DUO at 4 weeks is 99.89%.

If you had a high risk exposure - that means unprotected vaginal or anal penetration with an HIV positive person or someone who you strongly suspect is HIV positive AND you develop symptoms which are strongly suggestive of HIV infection - whish are very sore throat, very high temperature and a whole body rash at between 2 and 4 weeks post exposure, then a diligent doctor will want to retest you.

The Health Protection Agency algorithm for this scenario specifies a further HIV DUO - a 4th generation test, at one to two weeks later.

If that is negative then except in very exceptional circumstances outside the scope of this forum, then you can forget it.

I hope that clears that up.

best wishes, Sean
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