posted on Feb, 3 2006 @ 04:32 PM
Testing by saliva isn't all that new. Sweat is a new one to me, but a logical progression. Tests of this nature typically consist of a treated
piece of paper being used to collect the sample. The paper then changes color to indicate the presence of a target substance. However, by the looks
of this article, it seems they are just placing the swiped sample in a GC-Mass, which I will discuss. In either case, I suspect urine testing will
remain dominant because of how cheap it is and the ability to isolate what is detected.
When taking a urinalysis (pee in a cup) the testers are looking for drug metabolites, not the drugs themselves. Metabolites are the molecules
leftover from the metabolic processing of the chemicals. THC metabolites, for example, are fat soluble. They are stored in the body's fat and
released into the blood, where they are readily filtered by the kidneys.
A urinalysis first goes to the Emit-5 panel assay. This is a broad screening that looks for metabolites of 5 different substances: cannabis,
coc aine, opiates, benzodiazepenes, and barbituates. Note it is just a screen. An Emit test can only determine that there is something
present, but cannot tell what it is. Tests are sent for the Emit because it is a very inexpensive and fast process, but also fallible. Dilution is
typically used to defeat this test. The Emit test has minimum cutoff levels for metabolite presence. It is possible to dilute the sample (through
injestion not suplementation) to bring the metabolite levels below the cutoff, however this also alters other properties of the sample such as
creatinine levels (produced at a fairly constant rate by the breaking down of muscle tissue), specific gravity, and pH. If any of these catagories
are askew a flag is thrown and the sample is rejected. There are many products on the market that are supposed to keep these samples in the normal
range, but most are just gimmicks telling the user to drink lots of water (which is what is really beating the test). There are also many causes of
false positives, false negatives, and generally incorrect results. Human error plays a factor, as well.
When something is found in the Emit, the sample is then sent to GC-Mass (Gas Chromatography Mass Spectrometry) testing. This isolates the actual
chemical compounds present and can determine what exactly has been detected in the sample. It is not possible to defeat this test (except for
substitution, of course). The GCM is much more expensive, and as such is reserved for positive test results from the Emit. The GCM is also not
always used. Often, for employment purposes, a failed Emit is sufficient for denial.
I don't see these swipe tests gaining a very strong foothold in the drug testing industry. Because of it's low cost, simplicity, and effectiveness,
urinalysis will most likely remain the primary method used, particularly for law enforcement.