At the 7-month follow-up (83% response rate), the ITT 7-day PPA rate was 36%. Thus, the abstinence rates in the current study would appear to be consistent with the success rates achieved in another WTQL study conducted a year prior to the current study. Few quitline studies have included biochemical verification that would Rapamycin manufacturer allow examination of misreporting of smoking status but existing studies suggest that misreporting may range between 10% and 30% (Ferguson et al., 2012; Walker et al., 2011; Zhu et al., 1996). Assuming misreporting of 20% in the current study, 6-month abstinence rates would be 32% and 31% for the 6- and 2-week combination NRT groups, respectively, versus 25% for the 2-week patch-only group. In this scenario, the 6% improvement with 2 weeks of combination NRT would potentially result in an additional 33,000 annual quits nationwide.

Thus, there would still be strong public health benefit associated with combination NRT even if substantial misreporting occurred. However, we cannot determine whether misreporting varied with type of treatment and this limits the strength of inferences that can be made. Another limitation is that the current study may have been underpowered to detect certain effects given that actual 6-month rates were substantially higher (>38%) than we predicted (approximately 18% for an enhanced intervention). The study was powered to detect a 6.4% increase due to an enhanced intervention (e.g., 18.4% vs. 12% in a standard intervention) but power to detect such an effect size (6.4% increase) is substantially reduced as proportions approach 50% (given the same sample size).

Such a reduction in power likely accounts for the nonsignificant main effect for NRT duration and the failure to detect any interaction effects. In summary, the current study shows that combination NRT for either 2 or 6 weeks significantly boosts abstinence rates when used along with other tobacco quitline interventions (counseling, online support, etc.), with 2 weeks of combination NRT being the most cost-effective intervention tested. Combination NRT as a quitline adjuvant has the potential to produce significant public health benefit if widely used, with an estimated 30,000�C50,000 additional quitters in the United States each year. Table 3.

Batimastat Intent-to-Treat (ITT) 7-Day Point-Prevalence Abstinence (PPA) at 6 Months Postquit and Cost Analyses by Nicotine Replacement Therapy (NRT) Group Supplementary Material Supplementary Table 1 and Supplementary Appendices A and B can be found online at www.ntr.oxfordjournals.org Funding National Cancer Institute (NCI) grant 1RC1CA144382 to S.S.S.; T.B.B. was supported by NCI grant K05CA139871. Clinical Trial Registry: clinicaltrials.gov Identifier: NCT01087905; registered March 15, 2010 (prior to enrollment of study participants). Declaration of Interests S.S.S.