Cummings 1989a.

Study characteristics
Methods	Design: Cluster‐randomized controlled trial Setting: Private practices of internal medicine and family practice, USA Recruitment: Patients were recruited by primary care staff, or by research staff in clinics
Participants	916 adult who smoked (446 control, 470 intervention). 56% F, 20 cpd, av.age 44
Interventions	Intervention: • Physicians received training on smoking cessation counseling in 3 x 1‐hour seminars • Practices were provided with free self‐help materials, stickers, quit date prescription pads, and posters. Nurses and office staff were coached on the program and supporting materials by a member of the research staff Control: usual care. No further description on what the usual care entailed was reported
Outcomes	Continuous abstinence at 12m Validation: CO levels (cut‐off not defined), salivary cotinine < 30 ng/ml Quit attempts Measures of provider implementation: Ask, Assist‐Self‐help, Assist‐Quit date, Assist‐Meds, Arrange
Funding Source	Grant # CA38337 from the National Cancer Institute and by the Henry J. Kaiser Foundation Faculty Fellowship in General Internal Medicine (SRC).
Author's declarations of interest	Not reported.
Notes	Strategy: Provider training + Outreach facilitation Level: Provider + Practice Comparison type: Multicomponent vs. standard care
Risk of bias
Bias	Authors' judgement	Support for judgement
Sequence Generation	Unclear risk	No details reported
Allocation concealment	Unclear risk	No details reported
Blinding of outcome assessors All outcomes	Low risk	Smoking status was biochemically validated
Incomplete outcome data All outcomes	Low risk	Attrition rates were under 50% and the difference between groups was less than 20%. The overall loss to follow‐up was 22.7% (n = 208/916 survivors); 24.9% (n = 117/470 survivors) in the intervention group and 20.4% (n = 91/446) in the control group were lost to follow‐up at 1 year
Recruitment bias (cluster RCTs only)	Low risk	Participants were affiliated with the practice before randomization
Balanced baseline characteristics? (cluster RCTs only)	Low risk	Balanced between arms
Adjustment for clustering in analysis? (cluster RCTs only)	Low risk	QUOTE: "Individual patients were the units of analysis for the results we are presenting. A few physicians were clustered by offices and patients were clustered by physician. We tested the effect of this clustering in other analyses in which the sampling variances were adjusted for cluster sampling. These adjustments had no discernible effect on significance levels and did not alter our conclusions. We also analysed our results using the physician as the unit of analysis... These results were similar to the results of the analyses in which patients were the units of analysis. Thus, we omitted them to simplify the presentation"