Betson 1998.

Methods	Setting: government outpatient clinic, Hong Kong Recruitment: smokers aged < 65
Participants	865 smokers, 92% male, 49% smoking > 10 cpd
Interventions	∙ No intervention ∙ Self‐help materials (Chinese translation of American Cancer Society booklet) ∙ Physician advice (1 minute, based on 4 As) ∙ Physician advice and self‐help booklet
Outcomes	Abstinence at 1 year (sustained from 3 months) Validation: poor response to request for urine specimen, so data based on self‐report
Notes	2 vs 1, self‐help with face‐to‐face contact 4 vs 3, self‐help as adjunct to advice Full paper provided by Professor Lam
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Table of random numbers used to allocate questionnaires to 4 groups placed in sealed numbered envelopes
Allocation concealment (selection bias)	Unclear risk	"Every doctor was given a set of sealed envelopes" Considerable imbalance in numbers in each group; unclear whether this was due to randomisation procedure or selection bias
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Abstract only; unclear if participants were aware of what other arms received, but within comparisons in this review, interventions varied by intensity
Incomplete outcome data (attrition bias) All outcomes	Low risk	36% lost to follow‐up, included in ITT analysis