The process of regular SAMHSA-mandated drug testing includes two basic steps: immunoassay check and more precise gas chromatographic analysis. Registered cutoff concentrations are different for different drugs. The samples taken from the tested person should come with detailed formal documentation.
Specimens
These days the main specimen for most of the drug tests is urine. In some cases hair, saliva or sweat may also be used (see the Table below for detailed information on the use of the listed specimens). Blood tests are getting rare since the half-life of drugs in blood is considerably shorter than that in urine, saliva, sweat and hair. However, in some cases blood test may also be taken in order to specify the concentration of drug in the donor’s body. This is used to understand how much time has passed since the last intake of drugs by the tested individual.
Table: Effectiveness of drug tests by different specimens.
| Specimen |
Positive
sides |
Negative
sides |
| Blood |
- Can be used to specify the concentration of drug
- Almost impossible to adulterate
|
- Considerably shorter half-life of drugs
- Phlebotomy is needed
- Low drug concentration is difficult to register
|
| Hair |
- Preserves high concentration of drug even long after the last intake
|
- Difficult testing procedure is required
- Drug deposition is different for different hair types
- High price of testing
|
| Saliva |
- Almost impossible to adulterate
|
- Comparatively low drug concentration
- Only a small volume can be obtained
|
| Sweat |
- Preserves a noticeable concentration of drug for 3-7 days after the
last intake
|
- Difficult testing procedure is required
- Only a small volume can be obtained
- High possibility of environmental contamination
|
| Urine |
- Can easily be obtained
- Easy to get the volume required for testing
- Preserves a noticeable concentration of drug for 2-3 days after the
last intake
|
- Easy to adulterate when collected without supervision
|
Long hair preserves a noticeable concentration of drug for weeks or even months after the last intake. However, the process of testing is a very complicated one, plus, it doesn’t show whether the tested individual uses drugs regularly or occasionally, whereas urine test does.
It is much more difficult to adulterate saliva or sweat than it is to adulterate urine. However, the process of testing saliva and sweat samples is very complicated too since the concentration levels are much lower there then they are in urine. Sweat samples are collected with the help of special sweat patches that are appropriate for one-time testing. Collecting enough material for further testing is almost impossible though.
For most drug tests the preferred specimen is urine. It is easily obtained in volumes large enough for the whole series of tests. The concentration of drug in urine remains high enough to be registered for two to three days after the last intake (for some substances, such as THC, this period is even longer – up to several weeks, especially in regular abusers). However, a positive result of the THC drug test doesn’t mean that the tested person is intoxicated, since it usually takes THC as short as several minutes (several hours for larger doses) to be deactivated by the liver.
