Many organizations require all of their representatives or employees to be free of any illegal or unwanted drugs. Some government and high-level corporate positions require a drug test or screening before hiring to ensure a candidate's qualifications. The high demands of law enforcement and military officers require drug-free personnel as well. Even competitive sports often include such tests to guarantee fair matches. However, drug screens are not synonymous with drug tests; there are important differences between the two.
Drug screens are used more frequently than drug tests because screens are more affordable, the results are easier to interpret and they are processed more quickly. Drug screens are highly reactive, meaning that they can reliably react to the presence of a drug. However, drug screens are not very selective, meaning that they can sometimes react to other, legal drugs as though they were illegal. Because they lack selectivity, drug screens often result in a false positive, which occurs when a test incorrectly indicates the presence of a drug.
Drug tests, unlike screens, are much more accurate in determining the presence of a drug. Drug tests are both reactive and selective: they reliably detect the presence of drugs but only very rarely result in a false positive. The drawback, however, is that drug tests are more expensive to conduct than are screens. Drug tests also require more expertise from the tester and a longer waiting period for the results.
Many institutions need a reliable drug testing process but either lack the resources to conduct testing regularly or have too many employees for drug testing to be practical. On the other hand, the unreliable drug screens are not a good choice either. However, it is possible to combine the two procedures. First, people are put through a drug-screening procedure. If they pass, they are done testing. If they fail, their sample is put through a drug test to determine whether their positive result was valid. This way the organization can enjoy the benefits of both types of testing without spending as much time or money in most cases.
Random Drug Tests
Another method of preventing drug use is through random drug tests. A random drug test is a scheduled drug-testing period, but the subjects are chosen at random. Although the people chosen to take the test are a small number of the overall group, most people will not risk drug use in case they are randomly chosen. Furthermore, because these tests have only a few participants, companies can generally afford the more accurate test rather than the screen.