Types of Tests

Nov 1, 2010

Different bodily specimens can be chemically tested to detect evidence of recent drug use.

Urine. Urine is the most commonly used specimen for illicit drugs and the one most widely accepted by federal and state regulators. Urine tests show the presence or absence of drug metabolites—residues that remain in the body after the effects of a drug have worn off. A positive urine test does not necessarily mean a person was under the influence of drugs at the time of the test. Rather, it detects and measures use of a particular drug within the previous few days and has become the de facto evidence of current use. Because alcohol passes rapidly through the system, urine tests must be conducted very quickly after alcohol consumption to ensure accuracy.

Breath. A breath alcohol test is the most common method for determining how much alcohol is currently in the blood. It entails blowing into a breath-alcohol device, and the results are given as a number, known as the blood alcohol concentration. This number shows the level of alcohol in the blood at the time the test was taken. These levels have been correlated with impairment, and the legal limit of 0.08 for driving has been set in all states. Under U.S. Department of Transportation regulations, a blood alcohol concentration of 0.02 is high enough to stop someone from performing a safety-sensitive task for a specific amount of time, usually 8 to 24 hours, and a reading of 0.04 or higher is considered to be a positive drug test and requires immediate removal from safety-sensitive functions. Under Transportation Department regulations, a person who tests at the 0.04 level may not resume job duties until a specific return-to-duty process has been completed.

Blood. A blood test measures alcohol or drugs in the blood at the time of the test. Blood samples provide an accurate measure of the physiologically active drug present in a person at the time the sample is drawn. Although a blood sample is a better indicator of recent consumption than a urine sample, there is a lack of published data correlating blood levels for drugs and impairment with the same degree of certainty that has been established for alcohol. In cases of serious injury or death as the result of an accident, the only way to determine legal intoxication is through a blood specimen. There is a very short detection period, as most drugs are quickly cleared from the blood and deposited into the urine.

Hair. Analysis of hair provides a much longer "testing window" than other methods, giving a drug-use history going back as far as 90 days. Like urine testing, hair testing does not provide evidence of current impairment, but rather only past use of a specific drug. Hair testing cannot be used to detect alcohol use. It is the least invasive form of drug testing; therefore, privacy issues are decreased.

Oral fluids. Saliva is easy to collect, harder to adulterate or substitute, and may be better at detecting specific substances, including marijuana, cocaine, and amphetamines and methamphetamines. A swab of the inner cheek is the common collection method. Because drugs do not remain in oral fluids as long as they do in urine, this method shows promise in determining current use and impairment.

Sweat. Collection relies on a skin patch that measures drugs in sweat. The patch looks like a large adhesive bandage, is applied to the skin and is worn for some length of time. A gas-permeable membrane on the patch protects the tested area from dirt and other contaminants. Although relatively easy to administer, this method has not been widely used in workplaces and is more often used to monitor compliance for individuals on probation and parole.

Source: U.S. Department of Labor.


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