Drug Detection in Urine and Hair
Drug abuse in the labor force is just one more challenge for the prospective employer, one that we all pay for in increased health costs and decreased worker productivity. Concerns about growing costs to companies and lost worker hours explain how, once such testing was possible, its use grew exponentially.
An article in Monthly Labor Review points out that 18% of Fortune 500 companies ran drug tests on their employees in 1985, 40% by 1991, and today more than half of these companies do so. A study from the late 90s found that 63% of employers overall did some type of drug testing, while the number was up to 75% in 2009.
The theory is that the money invested in drug detection and testing pays off for a company. The U.S. Navy claims it has a drug-free workplace, incorporating random drug tests that cost nearly $20 million a year. The price tag is large, but the Navy asserts that it has decreased the number of sailors who use alcohol or drugs by 57%, a savings of over $210 million a year. This computes to saving about $10 for every $1 spent on drug testing.
There are a number of ways to detect drug abuse.
Urine analysis is the cheapest, and can detect a recent single use, and thus it remains, to date, the most common means of drug testing in the U.S.
Saliva and sweat analysis is accurate and afford less opportunity for switching of samples. At this point they are significantly more expensive than a urine test. Neither is in frequent use at this time, although saliva testing is making inroads, particularly because it is less invasive than a urine test and equally accurate.
The most accurate--and by far the most expensive, and invasive--testing is blood analysis. It is currently not allowed in the Federal drug testing program and is therefore not a part of the following discussion.
Finally, good information about drug use can come from an odd source--your hair, perhaps the least invasive way of accessing a person’s system. Because the bloodstream actually fuels hair growth, hair analysis can detect drugs for longer periods of time after use. However, this method really only reveals heavy and continuous drug use.
A drug tester's purpose and pocketbook will mandate which type of analysis he/she will do.
Urine tests commonly screen for the following:
- Cannabinoids, a term which refers to a group of substances found in the cannabis plant. Usually the tester is looking for marijuana or hashish usage.
- Opiods, which include illegal heroin and opium plus legal--with a prescription--codeine or morphine, along with drugs like Vicodin (hydrocodone) and Oxyctontin (oxycodone).
- Amphetamines. This category also includes illegal drugs, particularly methamphetamine, plus prescription medications used to treat attention deficit hyperactivity disorder.
- Phencyclidine, commonly referred to as 'PCP,' or "angel dust."
- Benzodiazepines, which are psychoactive drugs referred to as hypnotics or anti-anxiety treatments. Common ones are Xanax (alprazolam) or Ativan (lorazepam).
If we throw in LSD, methaqualone, and anti-depressants, these drugs comprise over 85% of drug abuse cases.
Urine Drug Testing
There are two types of urine drug testing, the screening test, and the confirmatory test.
The screen looks for the classes of drugs listed above, using what's called an immunoassay.
This is a lab technique that uses binding between an antigen and an antibody. An antigen is any substance that causes your immune system to produce antibodies against it. In this case it's the drug. These antibodies are proteins the body's immune system produces when it detects harmful substances (antigens).
Antibodies are initially created by injecting the drugs into rabbits or sheep. Their immune systems will produce the specific antibodies. These antibodies are then extracted and utilized in drug screenings. When a urine (or hair) sample is combined with these, drug metabolites (or products of the breakdown of drugs within the system) in the sample bind with the antibodies, providing positive test results. [If there are no drugs in the sample, there is no reaction with the antibodies, and the test will be negative.]
The antibodies in the test are tagged with a fluorescent dye or radioactive substance, so the amount of fluorescent light or radioactivity measured after the test reveals the concentration of the tested drug.
The confirmatory urine screen is much more sensitive, and is generally used to test for the presence of a specific drug, as opposed to just a class of drugs.
It is also more complex, accomplished via gas chromatography/mass spectrometry (GC/MS) or high-performance-liquid chromatography (HPLC).
In gas chromatography, the sample is vaporized, or turned into gas, in the presence of a solvent, which will dissolve the vaporized substances. Each substance is unique, and will stay dissolved in the solvent for its own particular period of time, known as the retention time.
Thus the substance comes out of the gas at an expected time, and is then absorbed by a solid or liquid, which is put through a drug detection machine. During analysis, the machine plots the retention time. Because each drug of abuse has its own retention time, the presence of specific drugs will be revealed by the retention time plot.
Below is a comparison found in Compton, 2007; Heit and Gourlay, 2004; and Reisfeld, et al, 2007, of the initial screen versus the confirmatory one.
There is good reason for running both the screening and the confirmatory urine tests.
Note that the confirmatory test has the advantage of identifying a specific drug in use, but, on the flip side, is slower and more expensive. However, the greater sensitivity of the confirmatory test greatly reduces the chances of false positives.
|Gas Chromatography-Mass Spectrometry (GC-MS) or High Performance Liquid Chromatography (HPLC)
|Sensitivity (power to detect a class of drugs)
|Low or none when testing for semi-synthetic or synthetic opioids
|Specificity (power to detect an individual drug)
|Varies based on assay used - can result in false positives and false negatives
|Qualitative analysis; detects classes of drugs (Heit and Gourley, 2004)
|Quantitative analysis; identifies a specific drug
|Inexpensive (FDA five-drug testing kit ~ $1)
|More expensive, may not be paid for by insurance
|On-site - rapid
|Intended for use in drug-free population; may not be useful in pain medicine context
|Legally defensible results
The length of time between drug consumption and the ability to detect it varies widely, depending both upon the drug itself, and upon what type of drug test is being utilized.
For example, amphetamines can be detected in saliva within 5-10 minutes, in urine 2-5 hours, and in hair 5-7 days. They disappear after 72 hours from the saliva, 2-4 days from the urine, and over 90 days from the hair.
Marijuana can be detected within an hour in the saliva, and 2-5 hours in the urine, but a full 5-7 days in the hair. It disappears after 12 hours from the saliva, a much longer 7-14 days from the urine, and, once again, over 90 days from the hair.
Clearly certain drugs (for example cocaine, methamphetamine, opiates and PCP) are quickly excreted from the body, and usually 72 hours after use cannot be detected in a urinalysis.
This is why hair analysis, with its long window, is making inroads in the testing community.
How Drugs are detected in Hair
For hair testing, 50-60 stands of hair are cut approximately one and a half inches from the scalp, and then a radioimmunoassay of hair (RIAH) is made.
Hair testing, as explained by the U.S. Department of Justice, relies on the fact that growing hair absorbs drugs and their metabolites into its composition. .
Due to the way hair grows, a drug metabolite becomes embedded in the hair sheath while the hair is being formed in its follicle--and thus the metabolite leaves a permanent record of its presence within the user's hair.
Due to this incorporation of metabolites, and to hair's growth, as fed by the bloodstream, the radioimmunoassay will provide a timeline of drug use--both the quantity and the number of times a drug (or multiple drugs, even) has been used over a period of timed
Hair analysis can test for cocaine, marijuana, opiates, methamphetamine and phencyclidine.
Although nicotine, benzodiazepines, some antidepressants and mescaline have been detected in hair, these tests are still in the process of development, and hair analysis is not currently utilized to find these substances.
The clipped hair is dissolved in several solvents. The RIAH measures the drug molecules entrapped in the hair, and a lab will then analyze the liquefied sample using the same gas chromatography technique as urine testing, and also, again, by assessing the number of antibodies recognizing the specific drugs.
Despite the added expense, hair testing has significant benefits over urine testing:
- It increases exponentially the time in which a drug can be detected.
- Short periods of abstinence will not yield a false negative.
- Hair is much easier to handle and store than urine.
- Purposely contaminating a sample of hair is much more difficult than doing so with a urine specimen.
However, hair analysis, aside from being much slower than a urinalysis, won't detect drug use within the past 5 days.
And as an added point of interest, the testing can be done on hair from any part of the body, so baldness is no barrier. Samples of body hair--even the eyebrows--allow participation in the screening process.
False Positives in Testing
Overall, the drug tests in current use are highly sensitive, and are unlikely to miss the presence of a drug. However, at times they're too sensitive.
A positive result when no drug is present, called a 'false positive,' occurs in 1-2.5% of tests. That percentage is quite low, and even though we list some causes for false positives below, this should not be cause for alarm. Being upfront with an employer about over-the-counter medicines, prescription pills, or supplements in advance of the test can eliminate much confusion.
Which over the counter medicationscan cause a false positive result on a drug test?
Nighttime cold medicines, particularly liquid cold relievers, often contain codeine, similar to the much more powerful morphine. Some weight loss products, and certain nasal sprays and OTC asthma products can yield a false positive. Even iburprofen, or products containing it, have caused positive test results for marijuana. Some OTC cough or cold medicines contain the common cough suppressant dextromethorphan, which can cause a false positive result for opiates.
Certain prescription medications can lead to a false positive test, as well.
Antibiotics like ampicillin and amoxicillin are well-known for obscuring urine tests. Certain older antidepressants, including Elavil (amitriptyline) and Tofranil (imipramine), have caused people to test positive for opiates. It has been reported that Valium (diazepam) has yielded false PCP screens.
Even certain foods can throw off the testing--although they need to be consumed in large amounts. Many people seem to have heard that poppy seeds can cause you to test positive for opiates. They can--but not in the amount you'd eat on a salad. A quirky food-substance, hemp-seed oil, used as a nutritional supplement, can apparently yield a positive test for marijuana.
With the Obama Administration currently pushing for additional workplace testing, we are likely to hear more about drug screening in the very near future.