Urinalysis Drug Tests
Testing is most frequently performed on small samples of urine, although hair, saliva, and blood can also be used. Urine samples are collected by personnel under carefully controlled circumstances to avoid mismatches resulting in false positives, and to prevent adulteration of the specimen by the swapping of samples or the addition of foreign substances. In particular, urine samples heavily diluted with water can skewer results, and so highly diluted specimens are routinely rejected. In certain legal cases involving individuals known to be repeat drug offenders, personnel are usually required to witness the sample being provided in order to ensure that no adulteration has taken place.
Samples can be tested at the same site in which they were provided. More frequently, it is shipped to a large facility that specializes in mass-testing specimens. Care must be taken in shipping to ensure the integrity of the specimen, and those that indicate contamination are not processed. A special tamper-proof seal is routinely placed on bottles to indicate whether or not this has occurred.
A urinalysis test is then run to indicate the presence of various chemicals within the sample. This initial procedure is known as the screening test. A positive result for any of the substances marked for testing will result in the sample being run for a confirmation test. In this case, more advanced and expensive processes are used to ensure the validity of the positive result. A common process used in this second stage is GC/MS (gas chromatography/mass spectometry) in which the sample is analyzed at a molecular level for the specific substance that tested positive in the screening; GC/MS is known to be highly reliable.
Hair Sample Drug Tests
Hair is occasionally preferred to urine for purposes of testing, as it can indicate drug use that occurred up to three months prior to the taking of the sample, while urinalysis has an effective testing limit of 24 hours to seven days, depending on the substance being tested (with the exception of routine marijuana use, indications of which can linger in the system for several months). Blood is infrequently used for testing, but can be useful for determining the degree of alcohol ingestion. Blood testing must naturally be performed under extremely careful and sterile conditions.
Employment Drug Tests
Drug testing is usually performed for purposes of employment, and is also used in social work and the court system to ensure that an individual is responding to drug rehabilitation. An employer may also choose to have his present employees routinely screened for drug use. This has become a controversial procedure, raising questions of privacy rights, but has become extremely widespread in recent years. A less contentious issue is that of post-accident testing, performed to ensure that an individual sustaining a workplace injury was not operating under the influence of drugs at the time the injury was sustained.
