The primary outcome was 7-day point prevalence abstinence (biochemically confirmed) at the EOT and 6-month follow-up. Participants were classified as abstinent if (1) they self-reported abstinence and (2) they had a cotinine reading of ≤15 ng/ml. Of the total 412 self-identified Caucasian individuals successfully genotyped, 187 participants self-reported abstinence at EOT (45%) and 133 of these individuals (71%) provided a sample for cotinine verification. At 6-months, 118 participants reporting abstinence (29%) and 89 (75%) of these individuals provided a sample. Those who failed to complete the follow-up or failed to provide a biosample for biochemical verification were presumed to have relapsed, as per convention (67). Of the 412 individuals, 112 were biochemically verified as abstinent at EOT and 90 during 6-month follow-up.
