Biochemically confirmed 7-day point prevalence abstinence was assessed at end-of-treatment (8 weeks post-quit). All of participants′ self-reports of abstinence during study visits were confirmed by an expired CO level of less than 10 parts per million. Relapse was defined as any smoking on 7 consecutive days after the target quit date. Time of relapse was determined via timeline follow-up assessment (33, 34)and was available for 1015 subjects.
