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A New Era in Drug Testing

July 1, 2006
by Murray Lappe, MD
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Expanded collection options bring potential for tailored approaches

In the coming months, the U.S. Department of Health and Human Services will move to expand the kinds of specimens that may be tested under federal agency workplace drug testing programs. The proposed addition of hair, oral fluid, and sweat specimens to the currently sanctioned system of collecting urine samples results from a directed department process that began with a scientific meeting of SAMHSA's Drug Testing Advisory Board in 1997, where use of alternative specimens and new testing technologies for workplace drug testing programs was discussed.

In addition to the new alternative specimens, alternative technologies also will be allowed under the HHS proposal. These include the use of urine point-of-collection tests, or instant tests. This will mark the first time since 1989 that the “gold standard” drug testing program now overseen by SAMHSA has changed from a laboratory-based, urine-only testing standard.

Each of the alternatives that will be allowed under the HHS guideline brings unique changes to the process of specimen collection and analysis, as well as differences in the window of detection. From the shortest window of detection delivered by saliva samples (measured in hours to a few days), to the longest window of detection coming from hair samples (which can detect drug use for up to three months), these testing options will look at the human body from a variety of perspectives to seek better information.

It is still unclear how or when federal agencies will use these alternative tests. Each agency will take the guideline and determine which method best suits its needs. Although the guideline will not immediately apply to the U.S. Department of Transportation drug testing program, sources indicate that it may be only a matter of months before DOT begins the process of publishing a notice of proposed rule making, for all or part of the guideline, for DOT-covered employees. Although the regulatory process may begin as early as this summer or fall, these new methods are still more than a year from implementation because of the certification procedures that will be required for laboratories and allowed devices.

Examining testing options

Drugs can be detected in oral fluids within one hour of drug use, making this method useful in detecting very recent use. As with the other relatively new specimens for testing, less is known about the pharmacokinetics and disposition of drugs into oral fluid as compared to urine. Opiates, PCP, amphetamines, and cocaine enter oral fluid through passive diffusion of the drug from the bloodstream into oral fluid.

However, the active component of marijuana (delta-9-tetrahydrocannabinol) does not diffuse into oral fluid. The only way to detect marijuana use is through the presence of the parent drug (THC) in the oral fluid because the parent drug was present in the oral cavity. This raises some difficult technical questions, as second-hand marijuana smoke can enter the oral cavity and be detected at the extremely low levels of detection that must be employed to detect THC in the oral cavity. In addition, since the oral cavity is in a constant state of cleansing by oral fluids, THC detection may be possible for only up to six hours at these levels.

Positive oral fluid tests for marijuana will be helpful for post-accident and “reasonable suspicion” testing, since there will be a correlation between a positive test and the reason for testing. Preemployment oral fluid testing would have very limited value. Because of the variability of saliva swabs, HHS is proposing a “neat” read through collection of a “spit” sample.

Hair testing addresses the other end of the spectrum in detection. Since hair grows at a rate of approximately 1 cm per month, the 1.5-inch length of hair used in the testing will contain traces of drug deposited over the previous three months. Since the hair will not be cut all the way down to the scalp, several days or even weeks of recent drug use may go undetected if no drugs were used in the previous 90 days. Some controversy exists over hair testing, as data show that higher concentrations of some drugs (e.g., codeine, cocaine, amphetamines) are found in dark hair than in blond or red hair.

Unlike urine, hair, or oral fluids, use of a sweat patch detects drug use that occurred shortly before the patch is applied and continuously while the device remains applied to the skin. The window of detection for the sweat patch is for as long as the patch remains on the skin, offering a cumulative measure of drug ingestion. This method may be useful for addiction treatment programs and probation/parole testing to determine drug use while the patch is worn; a patch can be kept in place for up to one week.

With regard to possible test contamination caused by a drug present on the skin, HHS proposes that before the sweat patch is applied, the skin area be washed with soap and cool water or with a disposable towelette. The collector then must use alcohol wipes to clean thoroughly the skin area where the patch will be worn, prior to application.

The testing alternatives that could have the biggest impact on workplace drug testing programs offer opportunities for testing at the point of collection. Point-of-collection devices for drugs of abuse first became available in the early 1990s. These include noninstrumented devices with visually read endpoints as well as automated testing devices with machine-read endpoints. Drug tests conducted with these devices use competitive binding immunoassays, under the same scientific principle as the initial tests conducted in certified laboratories.

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