Cheung 2017.

Methods	3‐arm RCT. 2013 to 2016. Country: Hong Kong Setting: Shopping malls and public areas in all 18 districts in Hong Kong
Participants	1143 participants in the Hong Kong 4th QTW Contest in 2013. Adult daily smokers who smoked at least 1 CPD in the past 3 months with exhaled CO ≥ 4 ppm. Intervention groups: early‐informed (EI) n = 379, late‐informed (LI) n = 385; Control group: 379 Mean age 45. 208 (16.4%) women. Mean 15.2 CPD at baseline. Had secondary education (64.1%). Ethnicity not reported. Monthly household income (HKD) (USD 1 = HKD 7.8) Below 10,000 EI: 94 (24.8) LI: 108 (28.0) CG: 115 (30.3), 10,000 – 19,999 EI: 128 (33.8) LI: 129 (33.5) CG: 116 (30.6) 20,000 or more EI: 140 (36.9) LI: 131 (38.4) CG: 124 (32.8)
Interventions	All groups offered cash incentive if biochemically validated quit rate at 3 months (HKD 500/USD 64) Control Group: The control group was not informed about the incentive at any telephone follow‐up, but the validated quitters at either 3‐ and 6‐month follow‐up received the incentive at 6‐month follow‐up At 3‐month follow‐up, validated quitters participated in a lucky draw organised by the Council on Smoking and Health (COSH), in which each of the 5 winners obtained a gift voucher of HKD 10,000 (USD 1282). All participants were informed about this grand prize at the enrolment To ensure fairness, all quitters received the incentive, and once only All participants received brief smoking cessation advice based on the AWARD protocol at enrolment, 1‐week and 1‐month follow‐up, a pocket‐sized self‐help education card and a 12‐page self‐help booklet Experimental Groups: Early informed group ‐ At 1‐week and 1‐month telephone follow‐up, the early‐informed group was informed about the incentive, which was offered to the validated quitters at 3‐month follow‐up Late informed group ‐ At 3‐month follow‐up, the late‐informed group was informed that they would receive the incentive if they quit and passed the biochemical validation at 6‐month follow‐up. Theoretical basis for intervention: Health Action Process Approach (HAPA) model Duration of intervention: 6 months Length of follow‐up: 6 months
Outcomes	Point prevalence abstinence at 6 months follow up, verified by exhaled CO ≤ 4 ppm and saliva cotinine level ≤ 10 ng/ml. Quit attempts (longest duration and number of quit attempts (no smoking for at least 24 hours)); cessation aids.
Notes	New for 2019 update ‘loose inclusion criteria for the study might have led to the inclusion of low‐rate/nondaily/light smokers who might simply stop smoking for a day in order to win. Such “cheating” was possible’ Funding: "This work was supported by the Hong Kong Council on Smoking and Health (COSH)." Decarations of interest: "Prof. Tai‐hing Lam is the principal investigator of the FAMILY project, which was funded by the Hong Kong Jockey Club Charities Trust. All other authors do not have connection with the tobacco, alcohol, pharmaceutical or gaming industries, and nobody was substantially funded by these organizations."
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Block randomisation was used to individually and randomly allocate the participants recruited on each recruitment day into 3 RCT groups. One investigator (YTCD) used random.org to generate random permutations of the 3 RCT groups and allocated these permutations to the blocks with a size equal to 3, 6 or 9. These blocks of permutations were assigned to the participant lists on each recruitment day. Other research staff conducted the telephone call and the intervention based on the allocation list at 1‐week and 1‐month telephone follow‐up
Allocation concealment (selection bias)	Low risk	All participants and recruitment staff were prevented from knowing the allocation procedures at enrolment
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemically validated
Incomplete outcome data (attrition bias) All outcomes	Low risk	Data completion at 6 months above 50% in all arms and no substantial between‐group differences: Early informed: n = 228, 60.2%; Late informed: n = 221, 57.4%; Control group: n = 228, 60.2%
Other bias	Unclear risk	Participants took part in a Quit and win contest (and may have already been randomised as part of that study) before being randomised to this trial. Potentially already motivated sample (incentivised by competition)