Ledgerwood 2014.

Methods	Country: USA Setting: University clinic, Michigan Design: 3‐arm randomized controlled trial
Participants	81 participants (17 Standard Care, 28 Traditional CM, 36 Early‐Treatment Enhanced CM). Participants were adult nicotine‐dependent smokers with Fagerström score ≥ 4 and English literacy. Exclusions: uncontrolled psychiatric disorders, substance dependence (except for nicotine and caffeine), in recover for pathological gambling, already receiving smoking cessation treatment. 50 (62%) female, average age 45 years, 27 (33%) European American, 53 (65%) African American, 1 (1%) Other ethnicity, average education 14 years, average cpd 16.6. Around average 1 year more education in CM participants than Standard Care participants.
Interventions	Standard Care: in weeks 2 to 5, CO and cotinine monitoring + 5 minutes counselling twice daily, 5 days a week. Participants received US$1 per sample submitted + bonus of US$20 for submitting all 10 samples in a week. Traditional CM: as Standard Care, + entry into prize draws. Prize urn contained 250 slips of paper, 50% with a reward: 44.8% Small (worth around US$1, e.g. snacks, toiletries), 4.8% Large (worth around US$20, e.g. gift certificates, electronics), 0.4% Jumbo (worth US$100, e.g. DVD player, gift certificate). On Day 1, participant drew for a prize if CO down by at least 3 ppm, and on subsequent days if CO down by at least 6 ppm. Number of draws available increased by 1 per day for every day abstinent, to a maximum of 5 at the end of the week. 5 bonus draws were awarded for Monday cotinine level ≤ 100 ng/mL in weeks 3 to 5. In total 180 regular draws and 15 bonus draws were possible. Enhanced CM: As for Traditional CM, but in the first week of prize draws a prize was guaranteed if test was negative. Cotinine‐negative tests also received a guaranteed prize. The guaranteed prize urn contained 91.2% Small, 8% Large, 0.8% Jumbo prizes. Subsequent weeks used a regular prize urn with 30% Small, 4% Large, 0.2% Jumbo prizes.
Outcomes	PPA, cotinine (≤ 100 ng/mL) and CO (≤ 6 ppm) verified, at 2 months and 6 months. Prize money won, attendance at CM schedules.
Notes	Traditional CM versus Standard Care is the comparison used in this review. Also in ISC.
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Statistician‐prepared sequentially numbered randomization envelopes concealed group assignment until assigned.
Allocation concealment (selection bias)	Low risk	As above.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical verification used.
Incomplete outcome data (attrition bias) All outcomes	Low risk	6m dropout by group: Standard Care 2/17, Traditional CM7/28, Enhanced CM 10/36. Differences not significant and ITT analyses performed.