C J Campbell wrote:
Takes one hell of a lot of popyseeds to test posotive.

A single bagel or muffin can cause you to test positive and there are
people
who have lost their jobs because of it. Because of this the drug test
is
being revised.

Yeah, it's been in the process of being revised for years. You can
keep revising until the cows come home, but until you're willng to
spend hundreds of dollars per test, the problem won't go away.

You see, drug testing is hard. It's sort of like doing oil analysis
(another practice I don't put much faith in) - you're trying to detect
tiny concentrations of stuff you care about in an organic fluid that
has been where the sun don't shine.

I don't know how much experience the rest of you have with this, but
I've actually done these analyses (both the kinds used for oil analysis
and the kinds used for drug testing) in an actual chemical laboratory
with my own actual hands (required lab course in my engineering
program), so let me share with you some of the pitfalls involved:

First off, when you're dealing with tiny quantities, everything must be
clean. Absolutely, positively, scrupulously clean. Breathe in the
wrong place, use a bit of the wrong soap, omit a calibration step, make
a minor error - and your results are garbage. A real world trace
analysis is usually multiple steps - and every one of them has to be
right every time. Second, you have to know what you are looking for
and what else can be there. Analytical chemistry is the process of
elimination. You can never really eliminate everything - that's what
makes field samples such a challenge. That's also what causes a single
poppyseed bagel to trigger a false positive for heroin. Kitchen
poppies and opium poppies are close relatives, and there is no simple
test to tell the digestive products of the two apart reliably in trace
quantities.

Another outrage is people who have too much water in their urine have
lost
their jobs because it was presumed they were attempting to disguise
their
drug use by drinking water. Of course, many diets encourage water
drinking
and flight crew in particular should drink lots of water to avoid the
dangers of dehydration.

The actual reason is keratinides. These are breakdown products
normally found in urine in certain concentrations. Excessive liquid
consumption will reduce their concentrations below normal levels, and
little else will. Low keratinine content is a pretty reliable
indicator that someone has been drinking a lot of liquids (not
necessarily water) and not sweating too much - meaning the kidneys are
working overtime. It's not likely to happen unless the person is
intentionally drinking a lot, but as you mentioned certain diets
encourage this and it's also considered proper for those working in a
very low humidity environment. The "problem" with this is that it can
cause the already diluted breakdown products of certain drugs consumed
days ago (most notably cannabis) to be diluted to such a low level that
the test won't work. This won't actually work if the person has enough
of the drug in his system to be actively impaired or if he has a very
high concentration due to chronic use, but it works pretty reliably if
the person is only an occasional user who has been clean for a couple
of days or more. Why we should care that the person is an occasional
user who last used days ago has never been adequately explained.

The bottom line is that ACCURATE drug testing (the sort that determines
the individual is currently impaired, and not fooled by poppyseed
muffins and who knows what else) is EXPENSIVE. Unfortunately, we do
not hold the drug labs liable for their errors. If they were not
protected from liability from their mistakes, they would soon go out of
business and the problem would solve itself.

Michael