A urine drug test detects the presence of alcohol and certain drugs in the body by measuring the interference of drug use with the body's capability to produce antigen-antibody complexes, explains Healthline. A person provides a urine sample in a specimen cup, and the nurse or technician examines the sample. A urine drug test usually consists of an initial screening method called an immunoassay and a confirmatory process called gas chromatography-mass spectrometry.
An immunoassay is the first part of a urine drug test, and it shows results on a color-changing test strip, according to Healthline. People who have positive results after an immunoassay undergo gas chromatography-mass spectrometry to confirm the results. Results are often immediately available after an immunoassay.
During the test, a person receives a specimen cup, leaves all belongings in another area, and sometimes wears a hospital gown, states Healthline. A nurse or technician may escort him to ensure he doesn't attempt anything that can change the results. The person covers the cup after providing a urine sample and brings it to the nurse afterward.
While immunoassays are fast and easy to take, there are possibilities of getting false positives, which means the test results are positive despite lack of alcohol or drug use, notes Healthline. In comparison, gas chromatography-mass spectrometry involves a longer waiting time but rarely leads to false positives.