A urine drug test is a process where a persons urine is analysed to detect the presence of illegal drugs. As with a regular urinalysis, it is vital to collect a midstream urine sample. This means that the first stream of urine is discarded, and only the middle part is collected in a sterile container. One to two ounces is sufficient for the test. It is recommended to clean the genital area prior to collection to ensure purity of the sample. Conventionally the first morning sample is most helpful.
1. Security Measures
To prevent switching samples with another personís urine, some testing methods call for the subject to be observed while urinating. This is obviously against the civil liberties of an individual however. One way to balance the personís right to privacy and the accuracy of the results of the test, some testing facilities require the subject to remove all personal belongings and wear a hospital gown. The collection is then done in a room where the subject does not have access to water that can be used to dilute the sample.
Some individuals attempt to subvert a urine test by drinking plentiful amounts of water. The testing facility, however, may counteract this by rejecting a sample due to its consequently clear color. In the event that such a sample is accepted, it is flagged and may be subjected to a specific gravity test. The normal specific gravity range of a urine sample is between 1.006 and 1.030 (higher numbers indicate higher concentration). A sample that is too dilute may be rejected; the dilution is noted in the report and sent back to the body that requested the test. As a general rule, the testing facility will not test a sample when the tamper-evident seal has been damaged.
2. Stages of Drug Testing
As with a routine urinalysis, the urine drug test may contain two discrete stages: (1) physical examination, where the color, specific gravity, clarity and concentration are noted; and (2) chemical examination, that tests for the specific illegal drugs of interest. A third stage in urinalysis, however, the microscopic examination, that identifies cells, casts and other components such as mucous and bacteris.
Analysis methods include:
- High performance liquid chromatography
- Immunoassay analysis
- Gas chromatography/mass spectrometry (GCMS)
GCMS is usually viewed as a confirmation test, as in the case when the result is contested when it turns out to be positive. There are some cases when a result turns out to be a false positive, where other interfering factors such as certain types of foods and prescription medication should be taken into account.
3. Home Tests
Another analysis method of the sample involves the on-site (or home) test, that usually consists of a chemical-laden card or dipstick that yields the result of the test in a very short period of time. Such devices can also be used to test saliva or sweat. As can be expected, these types of tests are prone to contamination and error. As such results from these are usually difficult to defend in a court of law, unless followed by an equivalent lab-based test.
Additionally, a full urine drug test (or routine urinalysis, for that matter) entail special apparatus and technical skills. These home kits only perform part of the full chemical tests, that may include urine glucose, urine pH, and urine ketones.
Drug testing in general has been a controversial subject ever since its introduction in the early twentieth century. Some have argued that it constitutes violations to a personís privacy.
Justification of its use has mostly been in the workforce scenarion, most notably in two situations: (1) pre-employment procedures, where the employer would want to minimize risk of hiring prospects with potential drug problems; and (2) post-accident drug testing, where certain circumstances may justify testing the employee involved to determine whether he or she was under the influence of the drug at the time of the accident.
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