Drug testing commonly involves the analysis of urine samples; however, it can also involve other forms of testing, including the analysis of hair samples. In a study published in May 2014 in the journal Drug and Alcohol Dependence, researchers from two U.S. universities and a private institution compared the accuracy of using hair samples to detect drug use to the accuracy of self-reports of drug use gathered through a questionnaire called the Alcohol, Smoking and Substance Involvement Screening Test, or ASSIST.
Drug Testing And Hair Samples
Drug testing of hair samples is based on the principle that a number of drugs enter the hair growing on the scalp after leaving the bloodstream. The procedure is also based on the principle that analysts can use the location of a given drug within a strand of hair to determine the general period of time during which drug use occurred. As a rule, it takes about a week to 10 days for a drug or the breakdown product of a drug to make its first appearance inside a growing hair.
This is considerably longer than the time it takes for drugs and drug byproducts to show up in urine. However, analysts can potentially detect substances in hair samples long after urine samples no longer produce usable results. Specific substances that may show up in hair include the breakdown products of marijuana, opioid drugs/medications and the breakdown products of opioid drugs/medications, phencyclidine (better known as PCP or angel dust) and the stimulant drug cocaine and its breakdown products.
The ASSIST Substance Questionnaire
The Alcohol, Smoking and Substance Involvement Screening Test comes from substance experts working for the UN’s World Health Organization. In addition to pinpointing the use of alcohol and tobacco, the questionnaire uses eight relatively brief questions to pinpoint the use of a range of other addictive or otherwise harmful substances, including amphetamine and the related stimulant methamphetamine, marijuana and hashish, opioid drugs, opioid medications, cocaine, inhalants, benzodiazepines and other sedative-hypnotic or tranquilizing medications, and LSD and other types of hallucinogens.
Specific issues covered by the eight ASSIST questions include lifetime involvement in the use of various substances, recent involvement in the use of various substances, frequency of substance intake, frequency of substance-related personal or social impairment, the relative ability to limit substance use, the level of concern that others express about your substance intake and any degree of involvement in injection drug use.
Comparing Accuracy Of Hair Sample Drug Testing vs. ASSIST Questionnaire
In the study published in Drug and Alcohol Dependence, researchers from the University of Maryland, Wayne State University and the Friends Research Institute used an examination of 360 adults with a moderate level of risk for drug use to compare the accuracy of hair sample drug testing to the accuracy of the reports made by people taking the ASSIST questionnaire. The hair testing, which covered a potential drug use period of three months, was performed with a well-established, widely used procedure and confirmed with a second standard procedure. The ASSIST questionnaire also covered a three-month time frame.
The researchers concluded that the highest degree of overlap between positive “hits” from hair sampling and results on the ASSIST questionnaire (86.5 percent) occurred when the subject was cocaine use. The next-highest degree of overlap between the two forms of testing occurred for amphetamine use (85.8 percent), then opioid drug or medication use (74.3 percent) and marijuana use (57.5 percent). Generally speaking, the results of hair testing detected the presence of various substances more than nine times out of 10.
However, self-reports of drug use made through the ASSIST questionnaire still provided more accurate results for all forms of drug intake under consideration. In addition, the researchers concluded that, in the case of marijuana and cocaine use, study participants with negative results on hair testing typically also reported lower levels of intake on their ASSIST questionnaires.
The study’s authors concluded that the proper testing of hair samples can play a helpful role in the detection of drug use in certain populations. However, since hair sampling can result in the underestimation of drug intake, they recommend that future research efforts on the subject either combine this form of testing with self-admissions of drug use or set a lower threshold for determining a positive “hit” during hair sample-based testing.