Drug assays or drug screening assays are tests that are performed to check for doping in sports or the presence of narcotic substances in the blood or in urine. Typically, due to the speed of results, gas chromatography, and mass spectrometry are the generally used methods of testing. However, for drugs that are made up of proteins and enzymatic material, assays are the preferred method. A common use of an assay is the immunoassay ELISA that gained popularity for being the preferred quick test for HIV positive patients. This test is also used for a whole variety of other diseases as well. This is because the test basically checks antigens against antibodies.
A drug screening assay is usually conducted prior to being employed. The test can either be asked of from a prospective employer or can be federally mandated. This is usually the case when one is going to be driving or operating some kind of heavy equipment. Pilots, drivers, and law enforcement officers are regularly asked to take drug tests before reporting for duty. Screening by private employers is usually only done once during joining.
An assay is a test for organic material specifically proteins. This can be used in drug testing through tests like ELISA and MTT. The MTT, and more recently MTS, are tests that are used to measure cytotoxicity to cells. The governing logic is that the test measures the amount of metabolic disturbance in the body. This can be used as a marker for narcotic substances since many of these do disrupt metabolic pathways.
There is absolutely no preparation that is required to be done for an assay. In fact, this is one aspect that most testers will insist on. What this means is that testers will try to achieve a picture of reality as much as possible. This is because there are many methods of trying to foil detection during drug tests. A statistic that is quite scary is that nearly 5% of random drug testing that is done in the States reveals a positive result and those that are done after specific incidents and accidents are much higher in positive results. One of the more crude yet effective methods of foiling a urine test is simply by having lots of water. What this does is to dilute the sample of urine so much that nothing significant shows up in the tests.