Drug abuse and addiction can cause serious psychological and physical health problems. In 2006, there were 1,742,887 drug-related emergency room visits nationwide, according to the National Institute on Drug Abuse. In 2009, 32.8 percent of 12th-grade students used marijuana. There are situations in which drug testing is advisable, and hair drug testing is used by law enforcement officials, employers and parents. It is effective and accurate for long-term drug use and can detect even small amounts of a drug.
Which Drugs Can Be Tested
Cocaine, marijuana, opiates, methamphetamine and phencyclidine, or PCP, can be detected through a hair drug test. Nicotine, methadone, simple benzodiazepines, some antidepressants and mescaline have been detected in hair, too, but these tests are still in the process of research and development. To rule out the possibility of external contamination, such as by marijuana smoke, testing labs look for both drug and its metabolites, or by-products, produced by the body.
Hair Sample
According to Omega Laboratories, a standard hair test requires 60 or more milligrams of hair, cut as close to the scalp as possible, or approximately 90 to 120 strands, depending on the hair thickness. Each half-inch of head hair provides a 30-day history of drug use. The standard is to test 1.5 inches of hair, or a period of approximately 90 days. If there is not enough head hair, body hair can also be used, but due to the slower growth, the time-frame represented is approximately one year.
Laboratory Analysis
After consuming drugs, the body processes them into drug metabolites, which the bloodstream carries to the hair. They enter the hair follicle and move into the hair strand where they remain embedded inside the hair shaft. Specialized laboratories extract the drug metabolites from the hair sample and purify and concentrate them. They test them by various chromatography methods -- laboratory techniques that separate and analyze specific components in a mixture, and also by antibodies that can recognize specific drug molecules.
Confirmation
Antibodies that test for the drugs can sometimes mistake prescription medications for drugs, and thus cause a false positive screening result. To eliminate that possibility, laboratories have to confirm all positive results for methamphetamine, opiates, PCP, cocaine and marijuana. The method used is gas chromatography-mass spectrometry, or GC-MS, which combines two standard chemical techniques to identify different substances within a test sample.
Advantages and Disadvantages
When compared to the standard urine testing, hair drug tests can detect a longer period of drug use. Many drugs, with the exception of marijuana, are rapidly excreted from the body, making them undetectable in urine if the test is done more than two to three days after use. Since the drug metabolites reside inside the hair shaft, bleaches, shampoos and other chemicals cannot alter the sample. Additional advantages include non-invasive collection procedures and easy sample storage. The limitations of hair drug testing are hair length, high cost and the inability to detect very recent drug use.
