At least with urine tests though, in theory, a methamphetamine test is supposed to only react to methamphetamine since between 60-75% of a dose of meth is excreted unmetabolized. As in it comes out of you exactly the same chemically as when you ingest it....
idk how saliva tests work, but i have heard that methamphetamine urine tests are one of the least accurate tests in the sense of false positives from a plethora of otc/rx medications.
I wouldnt put money on any instant non lab test being able to differentiate that well between methamp and damp.
googling methamphetamine saliva test produced this manufacturers site
http://www.accubiotech.com/templates/T_yestem_News/index.aspx?nodeid=49&page=ContentPage&contentid=211
It lists damp as reactive, as an active metabolite that it checks for. Now given the ones you guys have or whatever could be completely different but yeah