Mak 2020.

Study characteristics
Methods	Study design: RCT Location: Hong Kong Setting: primary care Recruitment: from 6 primary healthcare centres Study dates: 2012‐15
Participants	N = 144 Specialist population?: no Definition of smoker used: ≥ 1 cpd in the past 30 days Participant characteristics: 29% female; average age: 46 years; 22% primary education or less; 18% unemployed; 16% household income ≤ HKD 9999; 17% average cpd > 20; 38% high nicotine dependence
Interventions	Comparator: brief advice + self‐help materials Mode of delivery: face‐to‐face, written materials Intensity: brief 5 minute talk Pharmacotherapy: none Type of therapist/provider: not reported BCTs: 1.2 Problem solving, 4.1 Instruction on how to perform the behaviour, 5.1 Information about health consequences Intervention: ACT + self‐help materials Mode of delivery: face‐to‐face, telephone, written materials Intensity: 1 face‐to‐face ACT session and 2 telephone follow‐up sessions (each 15‐20 min) Pharmacotherapy: none Type of therapist/provider: experienced health counsellor trained in the principles of ACT applied in smoking cessation BCTs: 1.2 Problem solving, 4.1 instruction on how to perform the behaviour, 5.3 Information about social and environmental consequences, 12.6 Body changes
Outcomes	Definition of abstinence: 7‐day point prevalence Longest follow‐up: 12 months Biochemical verification: CO < 6 ppm was measured but validated quit rates are not reported Other relevant outcomes reported: none
Notes	Relevant comparisons: ACT + self‐help vs brief advice + self‐help Funding source: Health and Medical Research Fund of the Food and Health Bureau of the Hong Kong SAR Government (10111861) Author conflicts of interest: “The authors declare that they have no competing interests.”
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “The process of randomization was based on computer‐generated, block randomization with random block sizes, which were placed in sealed opaque envelopes."
Allocation concealment (selection bias)	Low risk	Quote: “The process of randomization was based on computer‐generated, block randomization with random block sizes, which were placed in sealed opaque envelopes."
Blinding of outcome assessment (detection bias) All outcomes	High risk	Although abstinence was biochemically verified, only unverified quit rates are reported and we were unable to obtain verified rates from the study authors.
Incomplete outcome data (attrition bias) All outcomes	High risk	Attrition was high: at 12‐month follow‐up 50.0% (35/70) were lost to follow‐up in the intervention group and 58.1% (43/74) in the control group
Selective reporting (reporting bias)	Unclear risk	Abstinence was defined as prespecified, although 12 month follow‐up was not prespecified. 6 month rates are not reported so unclear whether the reporting of 12‐month rates is an example of selective reporting