Drug Testing - The Definitive Guide
DRUG TEST METHODS
There are four basic ways to test a subject for drug use; Urine, hair, saliva and blood. Before continuing, I must say that this text mainly applies to urinalysis. However, I try to cover all drug tests.
It would be helpful if people could somehow find out which test they are getting ahead of time. Though caution must be taken. Asking your boss whether you're getting an instant or lab test or whether the test is a urine, saliva or hair test would imply that you know too much, or seem too curious. There are laws against discriminatory hiring practices and you should know what your rights as an applicant are. Look to your State’s labor laws before going on that next big job hunt.. Most are printed online.
Instant Test Devices
Instant tests enable parents to test their children. This is the most convenient and widely test being used. Employers and court systems use the tests to determine if your specimen screens non-negative and needs further confirmation testing in a lab. These devices can be as simple as a simple one drug dip stick test or as advanced as a cup with the test strip and adulterant check built in. For the stick type of devices, the tester dips the test end of the device into the urine, waits 2-4 minutes, and reads the results. The results will be either negative or non-negative. For the cups, you are given a cup, with the test strip covered by a peal-off type of sticker. Some cups test a portion of the urine while keeping the remainder aside for confirmation at a lab if necessary. Instant devices were never meant to be a device to determine if someone was positive for a banned substance. They should only be used to determine if a substance needs further testing through the lab.
Immunoassay
This procedure is best described in Thein and Landry's word's:
Immunoassays use antigen-antibody interactions to detect illegal substances. Antibodies that bind selectively to certain drugs or drug metabolites are chosen, and the sensitivity and the specificity of this test are only as good as the antibody chosen. The binding is proportional to the amount of drug in the urine and can be detected through enzymes, radioisotopes, or fluorescent compounds. With this technique, very small amounts of drug can be detected in a very small amount of urine, although this test may not differentiate between specific drugs within a class of drugs. Immunoassay has yielded false-positive results with some decongestants and non-steroidal anti-inflammatory drugs. Most are 97-99% accurate and false negatives are more common than false positives. Improper storage and handling are the cause of most faulty instant devices. Don’t store them below 32 degrees or over 90 degrees for any extended period of time.
Gas Chromatography
Gas chromatography uses a separation technique to divide the urine extracts into the component parts. An inert gas carries the urine through chromatographic columns, and the samples are separated by their boiling temperature and by their affinity for the column. Compounds are identified by separation time, called retention time. The retention time is unique and reproducible for each drug in a given chromatographic column.
Gas Chromatography / Mass Spectrometry
The most precise procedure for detection of banned substances is a combination of GC and MS. Gas chromatography/mass spectrometry is a two-step process, where GC separates the sample into its constituent parts, while MS provides the exact molecular identification of the compounds. Compounds are separated by GC and are then introduced, one at a time, into a mass spectrometer. As the sample constituents enter the MS, they are bombarded by electrons, which cause the compound to break up into molecular fragments. The fragmentation pattern is reproducible and characteristic, and is considered the "molecular-fingerprint" of a specific compound. Gas chromatography/mass spectrometry is considered to be the most definitive method for confirming the presence of a drug in the urine and is approximately 100 to 1,000 times more sensitive than TLC. Selective ion monitoring has been used to improve the GC/MS results. This procedure is standard for any and all specimens sent to a lab that have screened non-negative during the screening process.
The GC/MS is typically used to confirm "non-negative" EMIT and immunoassay test results. GC/MS will indicate precisely what chemical is present. This is necessary because the EMIT & immunoassay are only indicators of whether something similar to what's being tested is present. The GC/MS is difficult and more costly, which is why the EMIT and immunoassay screenings are given first. (Hewlett Packard produces the GC/MS equipment, including computer, for about $50-75k depending on options.) Abstinence and substitution are the only ways to defeat the GC/MS test. GC/MS is very precise when done right. However, it's still subject to human error. Inaccurate results are very rare. Most laboratories used today are Department of Health and Human Services Certified. They have been through a rigorous and lengthy testing process and have been found to be below the standard cutoff for errors in testing and/or reporting.
Hair Testing
When THC metabolites are in the blood, they go through the blood vessels in the head, and deposited into the hair. THC metabolites remain in the hair as a permanent record. The hair test costs a little less than a hundred dollars (anywhere from $65-$95) and is not used as often as urinalysis because urinalysis is cheaper (approximately $40-$70). Hhair tests are widely used in the casino industry. They cut approximately 50 strands of hair close to the scalp, and send it in to the testing lab where they wash it is washed then liquefied. A hair sample is dissolved in a series of solvents which extract the drug metabolites and then are analyzed via GC/MS. It can take several hours to days just to extract metabolites. Average hair grows 1/2 inch per month. Typically they just use hair one and a half inches from the scalp giving about 90 days of history. It has been rumored that labs can test as far back as 3-6 years. This is false. A lab will not test more than history the 1-1/2 inches of hair will reveal. If a collector splits, for example, 3 inches of hair into two separate samples and submits them as being from different donors, the labs cannot know the specimens are from the same hair. Labs frown on this as it would be considered fraud and is not common practice. The liquid is run through the GC/MS machine, and can detect as little as 1 ng/mL. Psychemedics Corporation has a home collection kit for $69. This home test kit is available if you want to test yourself before applying for a job. Also, parents can test their children.
Beating the hair test is extremely hard, Bleaching or dying your hair is reported to work, but it is very hard on the hair and permanent damage can be expected from such harsh treatments. I imagine you can shave every hair on your body and claim that you're a swimmer, but if you had hair at the interview, and suddenly, after you are informed of an impending hair test, you have no hair; you might be seen as trying to avoid the test.
Currently, the two most prevalent laboratories for hair tests are Psychemedics and Quest Diagnostics. Approximately 90% of all hair tests sent to laboratories are sent to one of these two powerhouses.
