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From: werner@aecom.UUCP (Craig Werner)
Newsgroups: net.med,net.motss
Subject: 2nd AIDS test approved
Message-ID: <1273@aecom.UUCP>
Date: Sun, 17-Mar-85 00:30:42 EST
Article-I.D.: aecom.1273
Posted: Sun Mar 17 00:30:42 1985
Date-Received: Mon, 18-Mar-85 00:07:51 EST
Distribution: net
Organization: Albert Einstein Coll. of Med., NY
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Xref: linus net.med:1227 net.motss:1221


	Dateline: last week (but I was busy):
	AP) The Government has approved a sec-
	ond screening test for blood contam-
	inated by acquired immune deficiency
	syndrome, or AIDS, after laboratory
	results indicating it was the most sens-
	itive indicator of possible exposure to
	the disorder.
 	  Electro-Nucleonics Inc. of Fairfield,
	N.J., was awarded the second license by
	the FDA ....

About 2 months ago, I ran a series of four articles on HTLV-3, the virus
that most likely causes AIDS. I spoke of the screening test as highly
accurate, and then received mail and flames otherwise.
	Well, here is the source of the misunderstanding. There are several
tests - the most sensitive being the Western blot, which I was referring to.
(This was reasonable, since most Test-Positive results were to be redone
with Western blots before accepting the results.) It has an accuracy of
99.8% or so.

	The first licensed test had an accuracy of approx. 93%. Tests under
development range from 82-95.6%.  These all use a system called ELISA (for
Enzyme-linked Immuno- S? Assay) which is much easier to do than a Western
Blot (Incidentally, Western Blot is so-called, because the first person
to do "blotting" was E.M. Southern, so the blot was nick-named the
"Southern Blot", and each new technique was given a different direction and
the name stuck.) ELISA involves add sample, add reagant, check color change.

	Anyway, this new test has an accuracy of 99.6% (4 false positives
in 1000 people)  which is not much worse than Westerns.
	
	AND, of course the usual disclaimer:  Although everyone with AIDS
has been shown to have antibody to HTLV-3, the reverse is not true.
The presence of antibody to HTLV-3 does not signify that a person has or
will get AIDS, but has merely been exposed to it or a cross-reacting virus.

-- 
				Craig Werner
				!philabs!aecom!werner
		What do you expect?  Watermelons are out of season!