Abdullah 2013.

Study characteristics
Methods	Study design: parallel RCT Country: China Recruitment: from a smoking cessation health centre ‐ smokers who called the booking line and attended the health centre during the study period were recruited by smoking cessation counsellor
Participants	562 smokers: aged ≥ 16 years, ≥ 5 cigarettes per day, clearly motivated to quit 78.3% men; average cigarettes per day: 18.8; average years smoking: 18.5
Interventions	1) 2 weeks of free NRT (patch or gum according to participant preference). However, participants were encouraged to use NRT for 8 to 12 weeks, sourcing the remainder themselves. 2) 1 week of free NRT (patch or gum according to participant preference). However, participants were encouraged to use NRT for 8 to 12 weeks, sourcing the remainder themselves.
Outcomes	PPA at 6‐month follow‐up; CO validated (< 9 ppm) Other abstinence measures: self‐reported 7‐day PPA at 6 months; self‐reported 24‐hour PPA at 6 and 12 months; self‐reported continuous at 6 and 12 months; quit for at least 24 hours at some point before 6‐ and 12‐month follow‐up Adverse events: not measured
Notes	70% of participants chose patch, 30% chose gum, with similar between‐group percentages The study was funded by the Hong Kong Council on Smoking and Health (COSH). Pfizer Consumers and Novartis partially sponsored the printing cost of the clinic pamphlets and provided some free NRT samples. Conflicts of interest: the authors declared no conflict of interests
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Quote: “The random numbers for group assignment were generated by the research assistant (not the counselors) of the project using a personal computer before subject recruitment.”
Allocation concealment (selection bias)	Low risk	Quote: “Eligible selected subjects signed the consent form and completed the baseline measures…before the counselor opened a serially numbered, opaque, and sealed envelope (SNOSE) to reveal the random assignment of each smoker to A1 or A2 group.”
Blinding (performance bias and detection bias) All outcomes	Low risk	Quote: “An independent interviewer, who was unaware of the subject’s group allocation, carried out the 6 and 12 months follow‐up interview.” Participants were aware whether they were provided 1 or 2 weeks of free NRT; however, it would be impossible to blind for this
Incomplete outcome data (attrition bias) All outcomes	Low risk	Dropout rates at 6 months were 75/278 in group 1 (2 weeks of free NRT) and 83/284 in group 2 (1 week of free NRT). There was therefore less than 50% dropout overall and rates were similar between groups.