General types of drug tests
Urine drug screening
When an employer requests a drug test from an employee, the employee is instructed to go to a collection site. There, the employee's urine is collected in a specially designed secure cup and sealed with a tamper resistant tape. The cup is then sent by express delivery service to a testing laboratory where it will be tested for several drugs. The first step at the testing site is to split the urine into two aliquots. One aliquot is first screened for drugs using an analyzer that performs immunoassay as the initial screen. If the urine screen is positive then another aliquot of the sample is used to confirm the findings by gas chromatography - mass spectroscopy (GC-MS) methodology. All test results are relayed to an MRO (Medical Review Office) where a medical physician reviews the results. If the result of the screen is negative, the MRO informs the employer that the employee is clean and has no detectable drug in the urine. However, if the test result of the immunoassay and GC-MS are positive, the MRO contacts the employee and tries to determine if there is any legitimate reason for the employee to have a positive result such as a medical treatment or prescription. The efficacy of urine testing is debatable due to systematic cheating as well as its questionable accuracy. In addition to false positive test results, it is widely reported that sample substitution and adulteration occur frequently, and both are effective methods of avoiding would-be positive tests. While most laboratories performing drug screens test for adulterants routinely, they can not keep pace with the various forms of adulterants available.
Adulteration tests analyze the properties of the urine to identify if the sample is abnormal. Such properties include the pH and specific gravity of the urine. They also test the level of creatinine, nitrite, glutaraldehyde, specific gravity, bleach and pyridinium chlorochromate.
Also, the wide availability of at-home drug screens allows an individual to take their own test before they receive one, thus knowing the results ahead of time- giving the user further opportunity to dilute the sample or to find a substitute. Yeast can be detected 9 to 11 days after consumption but will not show levels consumed.
