Buffels 2006.

Study characteristics
Methods	Design: Randomized controlled trial Setting: General practices, Belgium Recruitment: All patients screened for tobacco use
Participants	16 providers 1206 adults who smoked. Characteristics not described
Interventions	Common components in both groups: general practitioners received a 4‐hour training in giving advice to quit smoking Intervention: • General practitioners received training in performance and interpretation of spirometry, using a microspirometer • Participants received the minimal intervention strategy during a 12‐week period; those in a motivation stage 3 or 4 were asked to set a quit day and were offered a follow‐up contact as well as NRT and/or bupropion • Participaents also underwent spirometry and were provided with lung function measurement values and their flow/volume curve Control: participants received the minimal intervention strategy as described above but no spirometry
Outcomes	Smoking abstinence (undefined) at 24m Validation: Urinary cotinine (completed by 24.2% of self‐reported quitters) (cut‐off not reported)
Funding Source	Unconditional grant by Voorzorgskas voor Geneesheren, Brussels, Belgium
Author's declarations of interest	Not reported
Notes	Strategy: Provider training, spirometry Level: Provider, patient Type: Active vs. active (isolates spirometry) Unable to extract abstinence data for intervention group from full‐text. Attempt was made to contact authors unsuccessfully ‐ unable to include in meta‐analysis
Risk of bias
Bias	Authors' judgement	Support for judgement
Sequence Generation	Low risk	Coin toss
Allocation concealment	Unclear risk	No details reported
Blinding of outcome assessors All outcomes	Unclear risk	Smoking status was validated by urinary cotinine, but response rate was very low.
Incomplete outcome data All outcomes	Unclear risk	No details reported