of the blood thinners i'm on from my heart catheterization/stents procedure i had done. i was worried about nose bleeds from the swab being jammed up my nose, which i sometimes get from the meds i'm on, so they let me do the saliva test instead. non-invasive/a lot less stressful for me. even though sometimes it's hard to produce enough saliva for the sample when you're under pressure to get it done.