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Avatar universal

What effect will antibody have against HIV?

Hello Dr, I have been reading through a lot of posts and it was truly helpful, however there are some question that I could not figure out and I wish you might kindly give a hand:

1) why is the PCR test after 6 weeks not as reliable as ELISA? Is the PCR negative result after 6 weeks conclusive enough?

2) It has been said that the amount of virus will reach a peak at about 22 days after infection, and start to decrease then keep stable for a long period, why is this happening? If it is due to the antibody, then what will happen for those people who is not able to generate antibody(extremely rare)? Will they skip the incubation period and turn to AIDS very soon?
14 Responses
Avatar universal
There are no tests marketed or sold to give a conclusive negative test earlier than 3 months post exposure.  I don't know where you are getting your information but it is incorrect.
Avatar universal
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Avatar universal
Hi, a 4th generation test is 95% accurate at 4 weeks, at 6 weeks its considered 99.5% accurate and most doctors here in the uk consider it conclusive at 6 weeks! the British Association for Sexual Health & HIV and the government RECOMEND that you follow up with another test at the 3 month mark, not the manufacturers!! in america ALL states have not yet changed to the 6 week window because they look to the CDC for their guidelines.  Most states look to the CDC for their guidelines becasue they have little or no research going on in their own states regarding HIV transmission. The states that have the most advanced research and teh cities with the most experience with the epidemic (NYC and San Francisco) ALL quote a 6 week definitive window

The states that have the most advanced research and the cities with the most experience with the epidemic (NYC and San Francisco) ALL quote a 6 week definitive window!  
Avatar universal
No the UK does not consider it conclusive at 6 weeks.

UK Fourth Generation  Testing
Post testing
Page 11
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.
Avatar universal
ok m8 we will agree to dissagree, i never said that the manufacturers said their tests are conclusive, what i did say is the doctors most doctors say it, the doctors are out in the field doin the tests day in day out, the manufacturer say 12 weeks to cover themselves against lawsuit if anything were to happen, just like it says on a can of tuna that all care has been taken to remove bone but to take care!! its not that long ago the manufacturers were saying 6 months was conclusive,
Avatar universal

The Doctors that say 8 weeks is conclusive have probably  never ever seen a test turn positive after 8 weeks.
I doubt very much that with today's sensitive tests a negative 8 week test will turn positive at 12.
Having said that, I personally would not feel comfortable telling someone that he/she is conclusively negative after an 8 week test.
I didn't design the tests, I didn't evaluate the tests, it would be preposterous to tell someone that 8 weeks is conclusive if the manufacturer of the tests and the FDA still maintain the 12week guidelines.
12 weeks is just an additional buffer time frame to make sure the dates of the last possible exposure are covered and for some extremely rare individuals that may indeed need 12 weeks to produce detectable antibodies.
A PCR or DUO test is great for early detection, but early detection should not be confused with conclusively negative.
For now, only a test at three months can be truly considered HIV negative.

A negative at 6 or 8 weeks is indeed great news.

But unless and until the entities that set the guidelines change the window period 12 weeks shall remain the benchmark.
Avatar universal
" its not that long ago the manufacturers were saying 6 months was conclusive,"

That is true, but since then the tests have become far more sensitive.

They didn't just reduce the window period because they felt like it.
Newer tests and better understanding of the virus lead to that, not some opinion from a handful of doctors. Those things take time and careful analysis.

Avatar universal
It went from 6 month to 3 months in 2004.
Avatar universal
Hi Everyone,

Hi everyone -

Some clarification about testing here.

Our experts state that a DUO test is accurate at 4 weeks, and an antibody test is accurate at 6-8 weeks. Our members, who are not doctors, mostly prefer to state that all tests are conclusive at 3 months, based on what the test manufacturers say.

You are free to read it all and decide for yourself.

For more from our experts:




Also, please note that we allow and encourage everyone to post in any of our forums as long as they do so respectfully and are within our Terms of Use (http://www.medhelp.org/termsofuse.htm).



Avatar universal
There is no tests conclusive earlier than 3 months post exposure. No doctors on this forum or any other forum write the testing guidelines. US and  the UK  testing guidelines are 3 month post exposure to be conclusively negative.
Avatar universal
Oraquick Home Testing

Test approval date 07/03/2012

A negative result with this test does not mean that you are definitely not infected with HIV, particularly when exposure may have been within the previous 3 months.
If your test is negative and you engage in activities that put you at risk for HIV on a regular basis, you should test regularly.
Avatar universal
Hi, Darren!
I will answer your question, instead of my colleague Sean, if you don't mind. Differnet countries have different guidelines. However all these guidelines are back up with the appropriate scientific evidence. There are different tests in order to diagnose HIV. I gather that your test was the simple HIV1/HIV2 antibody test. In the UK, the approved guidelines regarding this test state that the window period is 12 weeks; however in the USA, this stands at 8 weeks. It is the same test but its licence in this country requires this specific period. This might change one day soon.
There is another test, the HIV Duo, which detects HIV1 and 2 antibodies, as well as the p24 protein of the HIV virus. If this is negative at 4 weeks, this would be conclusive.
Regarding your case, I think you can be quite reassured that a negative test at 8.5 weeks is a very positive sign, and I have never seen a single case of someone becoming positive after that, but we have to follow the current guidelines of this country. Most people, if they become infected, you can already detect antibodies very early on. The problem is when tests are negative, you can only be certain after a certain window period.
And, by the way, I totally agree with your statement about that remark from another website.
All in all, your risk from that single encounter is relatively low. For insertive vaginal intercourse is around 0.09%, and for insertive anal, 0.06%. even less, if you did not know the status of this lady.
Best wishes,
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