A drug screening is a quick initial scan that tests urine (or other bodily fluids such as saliva or blood) for metabolites or illicit substances, including marijuana, cocaine, and opiates. These screenings are generally pretty accurate. However, due to their generality, they can produce false positives. Current estimates approximate that up to 10% of failed drug tests in the United States can be attributed to false positives. Fortunately, most employers understand this limitation. Whenever a test comes back positive, the initial sample will be sent off for further, more in-depth analysis. This is known as a drug test. Drug tests incorporate much more sophisticated technology to confirm the presence of metabolites of illicit substances. The MS/GC (Mass Spectrometry/Gas Chromatography) test is the most common type of drug test performed. When the result of a drug screening comes back positive, the urine sample will be sent off to a third-party MS/GC testing facility for confirmation of the suspected metabolites. Although these tests are highly accurate, they are not used in the initial detection due to cost and overall involvement of the procedure.