Weissfeld 1991.

Methods	Study design: Randomized controlled trial Setting: Veterans Administration outpatient clinics, USA Recruitment: veterans attending walk‐in and general medicine clinics invited to attend quit smoking programme
Participants	466 male smokers av. age 55 years, av. cpd 26
Interventions	Therapists: smoking cessation counsellors 1. Control: Pamphlet on hazards of smoking 2. Low‐Intensity counselling: Single session 20 ‐ 30 mins and S‐H booklet 3. High‐intensity counselling: Same initial session, with sustained contact of 3 m. 1 further face‐to‐face session, telephone calls and mailings, behavioural S‐H manual. Prescription and sample of nicotine gum and instructions for use
Outcomes	Abstinence for 1 m at 6 m (9 m for high‐intensity group, 6 m after last contact) Validation: nicotine metabolites in urine
Notes	Using validated quit rates there was no difference between 2 and 3, although self‐reported quitting was greater in 3. Main analysis uses 2 and 3 vs 1 with sensitivity analysis of 2 vs 1. Comparison of intensity uses 3 vs 2 39% of group 3 used nicotine gum vs 8% and 7% in 2 and 1
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Randomization: 2 stages; initially in 1:2 to control or intervention, then 1:1 to high or low intensity occurred after delivery of low‐intensity session. Random number table
Allocation concealment (selection bias)	Low risk	Consecutively‐numbered envelopes containing treatment assignment
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Biochemical validation of abstinence
Incomplete outcome data (attrition bias) All outcomes	Low risk	34 (7.3%) died or lost to follow‐up included in ITT analysis. More lost in high‐intensity group