What’s the procedure for lab-based testing of a urine specimen?
Sealed specimens are first examined and tested for possible adulteration, then subjected to two separate tests. If results of an initial screening (immunoassay) are positive for one or more drugs, then a second, confirmatory test (gas chromatography/mass spectrometry) is conducted for each drug showing up in the sample. This confirmation test, which is more sensitive and specific, helps determine whether substances are present at cutoff levels or above and whether over-the-counter medicines can be ruled out as possible causes of positive test results. Results from both tests must be positive in order for a positive result to be reported.
