They do the quick test first and if it comes up negetive they don't go to GC.It varies some as to how soon they get the results back. Depends on whether there is a lab in your area or whether it has to be shipped out but usually 3 days is the max.Usually an MRO would contact you within 2 or 3 days to ask you if you were taking any prescription meds or why you would show positive.With a DOT type job they always get the results back within 3 days.