Dignan 2019.

Study characteristics
Methods	Study design: 2 x 2 x 2 x 2 incomplete factorial RCT (15 possible treatment combinations) Country: USA Recruitment: self‐referral following promotion via radio, newspaper, flyers at community events, organised activities by American Indian Health organisations, markets, casinos, tribal headquarters, chapter houses. Participants were referred by pharmacists and healthcare providers at one study site.
Participants	254 American Indian smokers; willing to stop smoking within 3 months from date of recruitment. 36% men, age range: 18 to 80 years (63% under 50 years old), average cigarettes per day: 13, mean FTND: 6
Interventions	2 x 2 x 2 x 2 incomplete factorial design (15 possible treatment combinations) 1) NRT component: Minimal: 1 NRT product (nicotine patch or fast‐acting oral NRT) Intense: 2 NRT products (nicotine patch and/or fast‐acting oral NRT) 2) Pre‐cessation telephone counselling component: Minimal: 2 counselling sessions Intense: 3 counselling sessions 3) Cessation in‐person counselling component: Minimal: counselling on the quit date plus 2 additional sessions Intense: counselling on the quit date plus 3 additional sessions 4) mHealth intervention component: Minimal: 2 text messages daily Intense: 4 text messages daily Behavioural therapy components 2, 3 and 4 were collapsed for inclusion in meta‐analysis as no interactions between components were detected.
Outcomes	PPA at 18 months after target quit date Validation: CO monitoring (< 10 ppm) Adverse events: not reported
Notes	Funding: National Cancer Institute, United States of America, R01CA170336 Conflicts of interest: the authors declare no potential conflicts of interest. This study is new to the 2023 review update.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "Subjects were assigned at random to one of 15 groups…". No further information provided.
Allocation concealment (selection bias)	Unclear risk	Not specified
Blinding (performance bias and detection bias) All outcomes	High risk	No placebo or blinding
Incomplete outcome data (attrition bias) All outcomes	High risk	Total sample followed‐up at 18 months: 16 participants, < 50% of the total sample