i was a patient in a pain managment clinic for two years. they preformed saliva drug screens for me only, i have little or no saliva, the swabs never once turned blue even though i was wearing fentanyl patches and also taking oxycodone daily. several screens came back negative for oxycodone? and the ones that did show oxycodone showed it at very low levels. i was discharged after 2 years because of saliva screen results.