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Rapid insti test better than Western blot?

Jan 25, 2013


Please take a look at this press release:

It mentions that Insti rapid test is more sensitive to a regular WB. It can detect antibodies 9 full days earlier than a WB. Do you agree? What do you make of this finding?

What is the point of having WB as a confirmatory test then?

Can rapid test now be used as conclusive tests rather than preliminary tests?

What do you think of a negative rapid test at 7 weeks post exposure? Conclusive or no?


Response from Dr. Wohl

This is a rapid test for HIV antibodies. It is sensitive, apparently even more so than many other antibody tests on the market. In a diagnostic test you want sensitivity (that is, an ability to find what you are looking for) and also specificity (what you found is really the thing you were looking for). So the rapid test is like a big fishing net and it is great at catching sea creatures. The Western blot makes sure that the 'fish' it catches is really HIV and not something else (like a false positive).

You still need a confirmatory test even if you have an ELISA that is very sensitive.

Now, the question really is do you need confirmatory testing if a p24 (included in the combo tests) is positive. Problem is that these combo tests don't tell you which was positive, the antibody or the antigen. If you knew it was the antigen, one could argue to forego the Western blot.


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