From: [gregt 10548] at [aol.com] (GregT10548)
Newsgroups: talk.politics.drugs
Subject: Re: Comment on drug testing
Date: 20 Sep 1994 20:43:02 -0400

[a--d] at [qed.uucp] (Chris Auld) writes:

{munch}
>And now, the point of this post: does anyone
>know if estimates of p and q exist?  And what would be a reasonable
>guess for d?  (If anyone could point me to a relevant paper on this
>isse, as I'm sure I'm far from the first person to note this, I would
>be appreciative.)

"The Other Side Of Drug Testing"  William L. Holstein
CHEMTECH  Sept., 1992.
American Chemical Society

120,000 tests in the aviation industry:  0.47% positive.
55,400 tests at 21 major airlines: 0.21% positive.
29,000 tests of federal gov. workers: 0.53% positive.
(My company: 2,500 tests: 0.86% positive.)

Accuracy: Highest accuracy reported in scientific literature: One(1) false
positive in 686 urine specimens.  Note that this is for the double testing
procedure: immunoassay screening followed by confirmatory Gas
Chromatography/Mass Spectrometry.  Immunoassay alone is notoriously
unreliable.

Note: The limits of the drug or drug metabolite present in the medium
being tested, blood, urine, etc., determines whether the test is positive
or negative.  Higher limits tend to result in more false negatives and
lower limits result in more false positives.  These levels are arbitrary
as far as I know

I have not seen any published data on the accuracy of negative tests.  It
seems that the companies are not that concerned with how many false
negatives they get back.  (Wait.....I don't guess that they really care
how many false positives they get back either.)

William Holstein calculated that from the above numbers the predictive
value of the tests ranged from 50% to 90%, or that between 10% and 50% of
all positive test results were false positives.

Anything for a safer workplace.

Greg Schorr

**********
You don't count the dead when god's on your side.

                         Bob Dylan
**********