Biochemical measures of substance use
Biochemical verification of tobacco, cannabis and other substances is completed at all study visits. Urine samples are collected and are tested for instant-read cotinine (a metabolite of nicotine; COT One Step Cotinine Test Device; cut-off of 200 ng/ml), cannabinoids (11-nor-9-carboxy-Δ9-tetrahydrocannnabinol [THCCOOH], cut-off of 50 ng/ml), and other substances (amphetamines, opioids, etc.). Instant-read cotinine tests are used to inform inclusion, as well as determining abstinence at weeks 2–12 to deliver incentives. Collected urine samples are aliquoted and frozen at all sites to be analyzed by a clinical laboratory for quantitative cotinine (level of detection of 50 ng/ml) and cannabinoid levels (11-nor-9-carboxy-Δ9-tetrahydrocannnabinol; THCCOOH; level of detection of 50 ng/ml). Breath CO samples are also collected at all in-person visits using the Micro+™ pro Smokerlyzer® from coVita.