Types of Urine Drug Testing

When drugs are introduced to the human body, they pass through the liver and are metabolized. According to Merck, a research-based drug company, the metabolizing of drugs is a process by which the body chemically alters the drug and produces metabolites specific to the drug. Urine drug testing is a method of detecting these metabolites in urine for the purpose of determining whether someone has used drugs.

Types

• There are two major types of urine drug tests. The first and most common of these is the Enzyme Multiplied Immunoassay Test (EMIT). This test uses antibodies that react only with the specific drug being tested for. If the metabolites of the drug exist in the urine, the antibodies will attach to them and change the color of the urine sample. The second, less common test is Gas chromatography-mass spectrometry (GC-MS). Scientific Testimony explains that that this type of test takes the sample and vaporizes it, separating the different components of the urine. Each component produces a spectral peak that can be individually identified, including any drugs that may be present.

Function

• Urine drug tests may be used to test for drugs during employment, after an accident to determine if impairment existed, or as part of a probationary program. However, the average person would most likely encounter a urinalysis drug screening as part of a pre-employment investigation. The EMIT screening is used to test for a basic panel of five drugs: marijuana, cocaine, amphetamines, opiates and phencyclidine (as established by the Substance Abuse and Mental Health Services Administration). More expansive tests are available. If a positive result is found in an EMIT screening, a GC-MS test may be administered to the sample to confirm the result.

Accuracy

• The University of North Carolina quotes the accuracy of the EMIT at between 95 and 97 percent, and the accuracy of the GC-MS at between 98 and 99 percent. In addition, the EMIT only has the ability to detect whether drug metabolites are present, not the amount of metabolites. The GC-MS can detect more specific levels of drug presence along with its higher level of accuracy.

Time Frame

• The testing itself only takes a few minutes to complete, but it may be a day or two before you receive the results of your test depending on lab work load and capabilities. If the result is a positive, the test may be sent away to an outside lab for confirmation testing, in which case the results may be delayed anywhere from an additional day to a full week.

Considerations

• In addition to testing for the presence of drug metabolites, urine drug tests also look for signs that the person being tested tried to alter the test results. Such additional elements of the test could include checking urine temperature to make sure the sample is fresh, checking for dilution of the sample and checking for substances that may have been used to contaminate the sample. To avoid having your sample rejected for one of these reasons, do not drink too much water the day of the sample and be sure to catch a mid-stream sample---not the beginning or end of the stream of urine.