Sutton 2007.

Methods	Setting: community, UK Recruitment: callers to UK Quitline (smokers planning to quit in next 30 days or who quit in last 14 days)
Participants	1506 including 344 (23%) recent quitters; 66% female, average age 38, average cpd 21
Interventions	All participants received telephone counselling and Quit information pack ∙ Standard letter ∙ Tailored 3‐page letter (based on social‐cognitive theory and perspectives on change model. Aimed to encourage and support smokers. Medium‐ or high‐dependence smokers advised to talk to their GP about cessation products)
Outcomes	Abstinence at 6 months; self‐reported as sustained for 3 months Validation: none
Notes	Tailoring; subgroup of baseline smokers showed larger effect of intervention, but effect was still not significant
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	"Randomization was effected by dividing days randomly within each of a series of consecutive 56‐day blocks into two equal sets, with allocation to group depending on which day the participant called the Quitline"
Allocation concealment (selection bias)	Low risk	"Randomization was carried out by a member of the research team who had no direct contact with the counsellors or the participants. Counsellors were unaware of which condition the participant was allocated to and would have remained blind unless the participant had happened to mention during a subsequent telephone conversation that they had or had not received a tailored letter"
Blinding (performance bias and detection bias) All outcomes	Low risk	Although no biochemical validation, participants received same telephone counselling and one‐off written material, so risk of differential misreport judged to be low
Incomplete outcome data (attrition bias) All outcomes	Low risk	Loss to follow‐up non‐significantly higher in control (24.4%) than in intervention (20.8%) Losses treated as smoking