Smith 2013.

Study characteristics
Methods	Study design: factorial RCT Country: USA Recruitment: callers to Wisconsin Tobacco Quitline from 1 April 2010 to 15 June 2010
Participants	987 smokers; aged ≥ 18 years, ≥ 10 cigarettes per day, willing to quit in next 30 days 42.4% men, average age 41.9, average cigarettes per day 20.7, 85% of participants' time to first cigarette was within 5 minutes, mode category for number of previous quit attempts was 2 to 5
Interventions	2 x 2 x 2 factorial design. There were 3 intervention components tested (detailed below) that were tested in different combinations, resulting in 8 study groups. 1) Nicotine patch versus nicotine patch plus nicotine gum 2) Two weeks NRT versus 6 weeks NRT 3) Standard counselling versus medication adherence counselling For the purposes of this review, we are interested in comparisons 1 and 2.
Outcomes	30‐day PPA at 6‐month follow‐up Other: 7‐day PPA at 6‐month follow‐up Validation: none Adverse events: not measured
Notes	Participants randomised to 6 weeks of NRT were sent an initial shipment of 4 weeks NRT. If they indicated interest in receiving additional NRT during a subsequent call, they were sent an additional 2 weeks supply of NRT. Factorial trial. Tests were carried out for interaction effects and none of these were found to be significant. We have therefore combined study arms to provide 2 comparisons (patch versus patch plus gum and 2‐week versus 6‐week duration). Participants received up to USD 50 for completing follow‐up assessments. Study supported by National Cancer Institute grants 1RC1CA144382 and K05CA139871 Conflicts of interest: "S.S.S. has served in the past 5 years as a co‐investigator on research studies at the University of Wisconsin–Madison that were funded wholly or in part by GlaxoSmithKline and Pfizer. T.B.B. has served as an investigator in the past 5 years on research studies at the University of Wisconsin– Madison that were funded in part by GlaxoSmithKline. T.B., B.M., and S.M.Z. are employees at Alere Wellbeing and also own stock in Alere Wellbeing (formerly Free & Clear, Inc.), an organization providing quitline services in Wisconsin. T.A.M. was employed by and owned stock in Free & Clear prior to being appointed Director of the Office on Smoking and Health, CDC, in September 2010. He was also an unpaid member of the Board of Directors of the nonprofit North American Quitline Consortium. T.A.M. has no current financial disclosures. M.C.F. has served in the past 5 years as an investigator on research studies at the University of Wisconsin‐Madison that were funded wholly or in part by Pfizer, GlaxoSmithKline, and Nabi. From 1997 to 2010, M.C.F. held a University of Wisconsin named Chair for the Study of Tobacco Dependence, made possible by a gift to the university from GlaxoWellcome."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "The 2 × 2 × 2 design yielded eight possible treatment combinations; participants were randomly assigned to the eight treatment combinations via a list of randomized numbers generated by SAS Proc Plan (SAS Institute Inc., Cary, NC)"
Allocation concealment (selection bias)	Unclear risk	Quote: "After initial phone screening by quitline registration staff, participants were transferred to a Quit Coach® (trained cessation counselor) at the quitline who completed consent, a baseline survey, enrollment, randomization to treatment, and provision of prequit counseling"
Blinding (performance bias and detection bias) All outcomes	High risk	No blinding of participants. Staff collecting outcome data were not affiliated with the quit‐line, but it is unclear whether they were blind to group allocation
Incomplete outcome data (attrition bias) All outcomes	Low risk	> 50% participants followed up at strictest quit time point. Similar follow‐up between arms