HIV-1 IU - (Jun/08/2010 )
Hi
I am not sure exactly where to post this, but the general discussion seemed to be the most appropriate.
I am wondering if anyone knows what 1IU of HIV-1 is in terms of something that relates to the actual virus (absolute number of virusses or the number of infected T-cells, etc)
A number of test give a range of IU of HIV-1 that it can detect:
-Amplicor standard protocol, 400–750000 IU/mL;
-Amplicor ultra-sensitive protocol, 50–75000 IU/mL;
-BioMerieux NucliSens, 80–10000000 IU/mL;
-Versant, 50–500000 IU/mL.
Logically (to me) it would seem that an HIV test should yield a value of 0 for a un-infected person, but obviously due to the fact that the lower limits of all the tests is some non-zero value this is not the case, so some threshold value is being used.
And I am wondering if anyone knows what the threshold value of IU is for the decision whether a person is infected with HIV or not (If a test gives a value higher than the threshold then it shows infection but if it is below it show no infection).
(I apologize for any ignorance on my part as this is not my primary field of training/study)
Thanks
well, to start answering your questions :
1- as you have written IU = a value, depending on the kit you are using.
i can't remember the exact copies/ml it equals on the kit i was using...
but, doing a good search on your kit... you will find it.
2- the negative result issue, the device is designed to read/detect the virus copies ...
once there are copies, less than a threshold it will be considered negative.
in your own logic mind,, you would say that if there is a virus it should be positive regardless of the quantity,,
right ?
i would say the same though ...
but, in real-time PCR machines you can detect the virus in low quantities i.e the lower limit of detection is
a low one in order to detect the virus once it enters your body. ( high sensitivity ).
hope ive helped you in a way or another ...
nightingale on Jun 9 2010, 06:34 PM said:
1- as you have written IU = a value, depending on the kit you are using.
i can't remember the exact copies/ml it equals on the kit i was using...
but, doing a good search on your kit... you will find it.
2- the negative result issue, the device is designed to read/detect the virus copies ...
once there are copies, less than a threshold it will be considered negative.
in your own logic mind,, you would say that if there is a virus it should be positive regardless of the quantity,,
right ?
i would say the same though ...
but, in real-time PCR machines you can detect the virus in low quantities i.e the lower limit of detection is
a low one in order to detect the virus once it enters your body. ( high sensitivity ).
hope ive helped you in a way or another ...
I had no idea IU was dependant on the test that is being used, from my basic knowledge I assumed it to be some kind of international standard. I have to admit this makes it kind of useless to compare different tests.
Seeing this, it would mean that there is obviously no set threshold to determine whether an infection is present.
I also had a bit of a look around on the different manufacturers websites, but it doesn't seem that they are to keen to share the specifications of their tests.
Thanks for your help
IU stands for Internationl Unit.
what i meant was : in your own kit leaflet/insert you will find the formula that converts virus copies from copies/ml to IU/ml.
so, when you are to compare test results, run on two different machines/ used two different kits,,
you should convert the result from copies/ml to IU/ml so your comparison will be a useful one.
and pay attention to the lower limit of detection between both.
this is from my own knowledge,,
any other notes are welcomed 
best wishes.
Hi Sir, just have a look at this and see if you find something that could help you,
best regards
nightingale on Thu Jun 10 07:40:20 2010 said:
IU stands for Internationl Unit.
what i meant was : in your own kit leaflet/insert you will find the formula that converts virus copies from copies/ml to IU/ml.
so, when you are to compare test results, run on two different machines/ used two different kits,,
you should convert the result from copies/ml to IU/ml so your comparison will be a useful one.
and pay attention to the lower limit of detection between both.
this is from my own knowledge,,
any other notes are welcomed
best wishes.
At present viral HIV-1-dependent settings are too expensive for limited resources. In some countries, monitoring antiretroviral therapy now is more expensive than the treatment itself. In addition, some commercial tests have shown deficiencies when quantifying rare genotypes.