Sippel 1999.

Study characteristics
Methods	Design: Randomized controlled trial Setting: 2 university‐affiliated primary care clinics, USA Recruitment: Patients approached by research staff in practice
Participants	205 adults who smoked, average age 38 years, 62% F, 20 cpd
Interventions	Intervention: participants received advice and cessation information. Additionally, they spent 10 ‐ 15 minutes receiving spirometry, carbon monoxide analysis, interpretation and education Control: participants received advice and cessation information
Outcomes	Continuous abstinence at 6m Validation: None Secondary outcomes: Quit attempts > 24 hours
Funding Source	Funded by the American Lung Association of Oregon and the American Academy of Family Practice
Author's declarations of interest	Not reported.
Notes	Strategies: Spirometry + CO monitoring Level: Patient Comparison type: Multi‐component vs. standard care
Risk of bias
Bias	Authors' judgement	Support for judgement
Sequence Generation	High risk	QUOTE: "questionnaires were numbered consecutively at each clinic throughout the study period. Subjects receiving odd‐numbered questionnaires were selected as the intervention group and those receiving even‐numbered questionnaires were selected as the control group..."
Allocation concealment	High risk	QUOTE: "the nurses performing patient check‐in were blinded to the questionnaire numbers. As four to six nurses conducted patient check‐ins independently and simultaneously at each clinic, it is unlikely that any given patient would be preferentially enrolled into either study arm". It is unclear how the nurses were blinded to the questionnaire numbers.
Blinding of outcome assessors All outcomes	High risk	Smoking status was self‐reported and face‐to‐face was different between the groups
Incomplete outcome data All outcomes	Low risk	The overall loss to follow‐up was 15.6% (n = 32/205); 12.6% (n = 13/103) in the intervention group and 18.6% (n = 19/102) were lost to follow‐up at 6 months