Understanding AIDS Detectors: Key Principles of Clinical Use

[eagleone]

What are basic principles of clinically used AIDS (from blood) detectors ?

 

[Monique]

Well, first of all: AIDS is a syndrome, it cannot be detected by a test.. rather it is a combination of symptoms that give the diagnosis.

What you mean to say is how HIV (Human Immunodeficiency
Virus) is detected :)

I am not sure, it could be a multiple techniques.. let me look around..

 

[Monique]

There are basically two things that the test can detect: the virus by PCR (which hides inside of cells, not a very good target) or antibodies. A HIV test would detect these antibodies from blood. The problem though is that it takes three months for most people to generate enough antibodies that can be detected..

The test is ELISA (enzyme linked immunosorbent assay). I am not sure if you are familiar with this technique? Basically an antigen is placed into wells of a microtiter plate, then a purified sample of blood is added (with the potential antibodies). A second antibody, which is covalently linked with horseradish peroxidase is then added, which will amplify the signal of the first antibody. An enzyme is then added, if the horseradish peroxidase is present
(after washing steps) a color will develop, indicating a positive sample.

Interesting site: http://www.aidshivtest.com/ I guess it is based on the same technique as described above?

 

[eagleone]

Originally posted by Monique
Interesting site: http://www.aidshivtest.com/ I guess it is based on the same technique as described above?

Good link,
well, I guessed it could be done by that way, nevertheless I expected some more “physical” diagnostic method (faster.. maybe some sensitive spectroscopy).

AIDS test-> yes, mistake -> speeding ticket :)

 

[Monique]

I actually would have expected a high-throughput method like chips..

 

[eagleone]

Originally posted by Monique
I actually would have expected a high-throughput method like chips..

Yes of course, chips are under "must be included", for any modern and quanitative equipment :).
I just think that they don't post on the net all the tehnical and engineering data, I'll search for a better url...

greets!

 

[iansmith]

Originally posted by Monique
I actually would have expected a high-throughput method like chips..

Do you know how much a chip analysis cost compare to ELISA and PCR? You got the reason why they are using "older" methods rather than newer technology. You also require many sample for chips. Are you going to waste 1 chip for 100 people? It is not cost effective.

Originally posted by eagleone
Yes of course, chips are under "must be included", for any modern and quanitative equipment :).
I just think that they don't post on the net all the tehnical and engineering data

They are probably doing research on using chip and to minimize the false posisitive and false negative. PCR and ELISA having been used for more year and are optimize to have a minimun of false results.

 

[Monique]

I have done a whole genome expression study, using the HG-U133 A and B chips from Affymetrix, I am aware how expensive the chips are.. $2000 if I remember correctly.. I am not sure if that is just for A or for A and B. And that is without the cost of sample preparation and such.

Anyway, that is a whole genome thingie. For the HIV test, you've got much less target to worry about. I think it is not too difficult to optimize detection for such a thing as you say it would be. Sample size shouldn't be a problem, but that is depending on the impact of HIV on a region..

People just like to stick with things they know that work. I myself have done a LOT of work with radioactive isotopes, but good alternatives are available with fluorescent materials which can be automized too.. my boss didn't agree and rather had it done the old fashioned way.