Fair enough @fairlaneowner, I just wasn't sure if the red blood cells in the sample would react with the alcohol from the swab and create the PEth byproduct outside the body. Just a thought. I attached some information from the Substance Abuse and Mental Health Services Admin that has some interesting information on biomarkers including PEth test.
I still am waiting for my appointment with my provider who ordered the PEth test. The information in the SAMHSA brochure, which was directly referenced on my lab report, states that a single biomarker should not be damming and taken into context with other tests for a solid picture. This literature even says false positives are "unlikely but still unknown due to paucity of research".