If the qualitative screening test is negative the donor is cleared. If not, a second
confirmatory test must be carried out by a certified laboratory, testing another
portion of the primary sample, using a different methodology: gas chromatography
- mass spectrometry (GC-MS).
Similarly the police performs an initial (random) breath alcohol test and a
blood test for confirmation - or performs a confirmatory test with an evidential
breath test (EBT) device that prints out readings and calibration
status etc. Normally, when doing road side testing, the police are not
interested in testing of urine specimens as they will not provide any evidence of impairment
- or driving under the influence (DUI).
As a golden rule, screening and confirmation testing should be performed by
using the same specimen - or specimens with similar "Window of Detection"
(i.e. blood/breath/oral fluid/saliva).
Workplace drug testing has long been based
on urine testing, which can be performed: