Cummings (Priv) 1989.

Methods	Country: USA Design: Randomized controlled trial; Nested; Clustered Objective: To test if physicians who are trained to use the 'Quit for Life' (QFL) program are more effective in helping patients to quit smoking Methods of analysis: Chi² test for proportions and t‐tests for means; Multiple logistic regression (for proportions) and ordinary least‐squares (for means) and calculated adjustment rates from the partial slopes associated with a dummy variable; Individual patients were the unit of analysis Clustering adjustment made: No adjustment to presented data but separate analyses tested clustering effects Significance of cluster adjustment: Clustering effects were tested in separate analyses; These adjustments had no discernible effect on significance levels and did not alter the conclusion
Participants	Therapist description: Primary care physicians in private practice Eligible for study: n= 844 Randomized: Intervention n= 31; Control n= 28 Completed: Intervention n= 20; Control n= 18 Age: Not reported Gender: Intervention females n= 4; Control females n= 2 Patient description: n= 916 smoking patients not selected by motivation to quit Eligible for study: Not reported Randomized: Intervention n= 470; Control n= 446 Completed: Intervention n= 360; Control n= 364 Age: Intervention mean = 43 years; Control mean = 45 years Gender: Intervention mean = 53%; Control mean = 61%
Interventions	Setting: Private primary care internal medicine and family practice (primary care) in San Francisco, USA; Local hospitals at times that fit with the schedules of the participating physicians; Four who were unable to attend the second sessions received the training privately in their office Training of those delivering the intervention to the health professional: Not described Intervention description: Training (personalised advice, quit date, one follow‐up visit, self help materials and nicotine gum) Control description: Normal care (no training) Duration of intervention: Three, one hour seminars Intervention delivered by: Internist or psychologist Intensity: Three, one hour seminars, second seminar one or two weeks after the first, third seminar four to twelve weeks later
Outcomes	Pre‐specified outcome data: Demographic characteristics; Smoking history; How much do you want to quit smoking; How confident are you that you will not be smoking one year from now; Pressure to quit from family and friends; Was smoking discussed; Did you receive a self‐help booklet; Did you receive a follow‐up appointment about smoking Follow‐up period: Twelve months
Notes	Process measures: None reported Validation: Expired carbon monoxide and serum cotinine Manual adjustment for potential clustering effects performed in the meta‐analyses for primary outcome data
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Authors state patients were randomly assigned however methods not described
Allocation concealment (selection bias)	Unclear risk	Methods not described
Blinding (performance bias and detection bias) of participants	High risk	Due to the nature of the intervention blinding of participants was not possible for this study
Blinding (performance bias and detection bias) of outcome assessors	Low risk	Authors state outcome assessors were blinded
Incomplete outcome data (attrition bias) All outcomes	Low risk	Participants assumed smokers if lost to follow‐up or abstinence unable to be biochemically verified; Missing outcome data accounted for in analyses
Selective reporting (reporting bias)	Low risk	All expected outcomes, including those that were pre‐specified were reported
Other bias	Low risk	No other biases identified
Imbalance of outcome measures at baseline	Low risk	Imbalances adjusted for using logistic regression
Comparability of intervention and control group characteristics at baseline	Low risk	Imbalances adjusted for using logistic regression
Protection against contamination	Low risk	Members of the same group practice were assigned to the same condition to minimise cross‐over
Selective recruitment of participants	Unclear risk	More control participants were recruited by practice staff than intervention subjects; Methods of recruitment not clearly described