Next, the sample must be made testable. Urine and oral fluid can be used "as is" for some tests, but other tests require the drugs to be extracted from urine. Strands of hair, patches, and blood must be prepared before testing. Hair is washed in order to eliminate second-hand sources of drugs on the surface of the hair, then the keratin is broken down using enzymes . Blood plasma may need to be separated by centrifuge from blood cells prior to testing. Sweat patches are opened and the sweat collection component is removed and soaked in a solvent to dissolve any drugs present.
Random, or “spot,” drug testing is a strong deterrent to drug users because it is conducted on an unannounced basis. Using a random selection process (., computer-generated), an employer selects one or more individuals from all the employees included in the employer’s workplace drug-testing program. By using a random selection process, employers ensure that there is no bias and that all employees have an equal chance of being selected, even those who have been drug tested recently. Random drug testing can be more effective at detecting and deterring drug use than pre-employment testing because employees do not know when they may be selected for testing.