Leung 2019.

Study characteristics
Methods	Study design: parallel RCT Country: China Recruitment: referral by doctors and nurses from 20 primary care clinics across Hospital Authority
Participants	560 smokers; ≥ 10 cigarettes per day for ≥1 year; 85.2% men; average cigarettes per day: 18.6; FTND: 5.71
Interventions	1) Single therapy (nicotine patch) for 8 weeks plus counselling 2) Combined therapy (nicotine patch and gum ‐ 2 mg every 1 to 2 hours, as required) for 8 weeks plus counselling Patch dose regime mixed based on dependence (number of cigarettes per day before quitting) for both intervention arms: 10 to 19 cigarettes per day: 4 weeks: 14 mg, 4 weeks: 7 mg ≥ 20 cigarettes per day: 4 weeks: 21 mg, 2 weeks: 14 mg, 2 weeks: 7 mg Both groups started treatment on target quit day. Counselling was delivered by registered nurse trained in smoking cessation.
Outcomes	7‐day PPA at 52 weeks' follow‐up Validation: CO validated (≤ 6 ppm) Other abstinence measures: 7‐day PPA at 4, 12 and 26 weeks follow‐up; CO validated (≤ 6 ppm) Adverse events: cardiac AEs measured up to 1 year
Notes	Funding: nil Conflicts of interest: the authors declare that they have no competing interests. This study is new to the 2023 review update.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: "A statistician who was not involved in the statistical analysis independently randomized participants by using a predetermined random table generated by Microsoft Excel 2002."
Allocation concealment (selection bias)	Unclear risk	Quote: "The counsellor who had been concealed from the randomisation and allocation sequence, then assigned the patient to their specified intervention according to the allocated number". No further information given and therefore method of concealment unclear.
Blinding (performance bias and detection bias) All outcomes	High risk	Pharmaceutical intervention with no placebo control group.
Incomplete outcome data (attrition bias) All outcomes	High risk	52‐week retention rate: patch group: 92/286 = 32%; patch and gum group: 88/274 = 32%