Sometimes the body doesnt produce antibody untill 6 week?

Hello,

I have a couple of question about the 28 DAY DUO test.

a) Is it true the body sometimes doesn't produce HIV anti-bodys until 6 weeks or more? if thats true then maybe its because the the also would pick up any P24 of the HIV by 28 days which makes it 99.8% Conculsive.

b) However, how can the HIV DUO test be 99.8% conculsive for 'HIV 2' at 28 days if the body sometimes doesnt produce antibodys untill up until 6 weeks or more and HIV 2 does not produce P24 Antigen? Unless of course 99.8% of people have produced antibodys for HIV 2 normally by 28 days?

I don't mean to be argumentative I would just really love to know the awnser and would be most grateful.

Thank you.

[Dr Sean]

Good Morning,

You're not being argumentative - interesting question and actually not an uncommon one.

Your question a) is geerally correct. Over 99% of people will produce antibodies by 6 weeks so a 3rd generation test will identify over 99% of people by that time. Yes, the use of the p24 antigen as an addition improves the accuracy of the test at an earlier stage as described in and in the links on our HIV testing page.

Your question b) is more interesting. The answer lies in the fact that:-
1) HIV 2 is very rare in Western Countries being found predominantly in West Africa - for example in the USA there are many less tahn 100 cases of HIV 2 since the mid eighties hwen the pandemic began. It is more prevalent in European Mediterranean countries probably as a result of previous colonial activity in Africa.
2) although HIV 2 is found in West Africa it is not the dominant form - HIV 1 is
3) there is very considerable serologic cross reaction between the two forms of HIV 1 and HIV2 so HIV 2 for example is commonly - up to 90% in some cases - identified in testing for HIV1 alone
4) most people will form antibodies to HIV 1 and 2 after four weeks - certainly over 99% by 6 weeks
5) the serologic cross reaction applies to the antigen component as well ie the p24 will generate positive reaction in the presence of HIV2 although not specifically designed to do this


Consequently, the above combination of factors means that HIV 2 is overwhelmingly likely to be detected with the same level of accuracy at 28 days or more.

I hope that helps - Nice question thank you.

Sean

Hi Sean,

Thanks so much for your reply! The fact that you reply at such a good time is great. Really do appreciate it!

OK I got you! basically at the 29th day from possible exposure (which is when I will take my DUO) it will would be 99.8% accurate for HIV 2 and conculsive?

[Dr Sean]

Good Morning,

Yes, you are correct, the test at 29 days will be 99.89% certain for both.

Peopel do worry about the fact that the tests are "only" 99.89% but in practical medical terms thats nearly 100% and for my purposes it is.

kind regards, Sean

Thanks so much for that information!

I'm still worried and wanted to get your opinion of this from these next questions please,

1)

Quote
'If this is the same as a HIV Duo test (available in the UK and probably USA I presume) which tests for antibodies and P24 antigen (protein which forms part of the HIV Virus) is considered by the British HIV authority to be 99.8% accurate at 4 weeks.

This is because Antibodies become detectable approx 4-8 (occasional up to 12 weeks) after infection. P24 Antigen becomes detectable from 10 to 28 days after infection and is detectable up to about 10 months after exposure, subsequently a recent infection would by identified by the test picking up the P24 Antigen.

Only exception is a HIV 2 infection as this strain of the virus doesn't produce P24 antigen and therefore could take up to 12 weeks to be detectable. However HIV2 is exceptional rare and pretty much restricted to western africa.'

Source

http://www.ukcoalition.org/HIV-Test/23786.htm

Especially the last paragraph? The last paragraph surely can not be true due to what you explained previously? Where did that information come from in that statement? is it based on evidence? or just someones opinion do you think?

Question 2)

The Doctor today claims the The Duo test is 95% at 28 days, 99.8% after 3 months? Surley this is incorrect?

Question 3) I have look and looked and cant find on the British HIV Association website that acutally says that 'the HIV Duo test to be 99.8% accurate at 4 weeks'?

Thank you again

[Dr Sean]

Hello,

I've cut and pasted your further questions beneath:-

Thanks so much for that information!

I'm still worried and wanted to get your opinion of this from these next questions please,

1)

Quote
'If this is the same as a HIV Duo test (available in the UK and probably USA I presume) which tests for antibodies and P24 antigen (protein which forms part of the HIV Virus) is considered by the British HIV authority to be 99.8% accurate at 4 weeks.

This is because Antibodies become detectable approx 4-8 (occasional up to 12 weeks) after infection. P24 Antigen becomes detectable from 10 to 28 days after infection and is detectable up to about 10 months after exposure, subsequently a recent infection would by identified by the test picking up the P24 Antigen.

Only exception is a HIV 2 infection as this strain of the virus doesn't produce P24 antigen and therefore could take up to 12 weeks to be detectable. However HIV2 is exceptional rare and pretty much restricted to western africa.'

Source

http://www.ukcoalition.org/HIV-Test/23786.htm

Especially the last paragraph? The last paragraph surely can not be true due to what you explained previously? Where did that information come from in that statement? is it based on evidence? or just someones opinion do you think?I've actually answered this already but you have a different opinion from another source. You need to ask the ukcoalition that question, not me. Ultimately I suspect that they and I are saying the same thing but in a slightlty different way. You have picked out a general response from them but I have answered you specifically

Question 2)

The Doctor today claims the The Duo test is 95% at 28 days, 99.8% after 3 months? Surley this is incorrect?yes, that is incorrect and doesn't match the research or the individual companies advice. The HIV DUO will give you certainty of greater than 99.89% at 28 days or more

Question 3) I have look and looked and cant find on the British HIV Association website that acutally says that 'the HIV Duo test to be 99.8% accurate at 4 weeks'?You're right - they don't comment on that.

Thank you again

Once again thank you so much for that! REALLY appreciate it.

Just to copy and paste your reply,

Question 3) I have look and looked and cant find on the British HIV Association website that acutally says that 'the HIV Duo test to be 99.8% accurate at 4 weeks'?You're right - they don't comment on that.

I'm guessing the 99.8% accuracy then comes from your research and other Doctors like yourselves?

What it does say is

'The recommended first-line assay is one which tests for HIV antibody AND p24 antigen simultaneously.
These are termed fourth generation assays, and have the advantage of reducing the time between
infection and testing HIV positive to one month which is one to two weeks earlier than with sensitive third
generation (antibody only detection) assays [22]. It is reasonable to expect universal provision of these
assays, although they are not offered by all primary screening laboratories.'

Here it is refering to the 'one month' or 28 days mark for testing, is that correct? But doesnt actually say the accuracy of it?

Also I was reading on the Guidelines for
HIV Testing - Web consultation comments

'And I particularly welcome the recommendation that 4th generation assays that include the p24 test should be standard, thus reducing the window period to 15 days'

'we have above suggested the appropriate window period be 3 weeks for the recommended assay'

Wow thats thats pretty good, 15 days, so by 4 weeks that surley must be pretty conclusive.

"am concerned that there has not been an attempt to alter the statement regarding the 3 month
window period with respect to 4th generation assays for HIV testing. It is clear that these tests
have superior sensitivity to previous assays and I am yet to be convinced that anyone has seen a
patient recently who has tested negative with one of these tests more than 4 weeks after their
relevant episode of risk. Isn’t it about time BASHH made a stand and produced a document that
allows clinicians to have a consistent message to HIV window periods?"

Dr H. Hunter Handsfield also confirms in all his years of testing he has NEVER seen a patient who has tested negative at 4 weeks to later then turn positve. He I belive in American where in America they for some reason are still very behind the times with HIV testing.

Also in this British HIV Association it says

'nevertheless the 3-month window period that has prevailed for over a decade is not based on watertight evidence either, rather it is the “generally accepted view”.

'At GSTT we have advised staff to inform patients that our test has a 6-week window but some individuals (especially non-medical staff) are reluctant to alter their practice as BHIVA/BASHH guidelines still name 3 months as the necessary window period.'

All of this is very compelling and from Doctors who have vast experience and research in HIV test is that right?

[Dr Sean]

Good Morning

Again, thanks for the email but also, I have answered this. I'm going to close down this thread now to give other people a chance. Please make a donation to NAT.

best regards, Sean