can usually only be dected through GCMS testing. Fentanyl
is in the same class as Morphine, however, it is synthetic and does not metabolize like other opiates, ie Vicodin, Morphine, Codeine. The urine test is testing for metabolites, ie norhydrocodone, hydromorphone. It depends on the test that is being used and that the assay cutoff is for that particular test.