Kornitzer 1987.

Study characteristics
Methods	Study design: parallel RCT Country: Belgium Recruitment: worksite primary care clinic
Participants	199 smokers (average cigarettes per day 24 to 25)
Interventions	1) Nicotine gum (4 mg) for at least 3 months 2) Nicotine gum (2 mg) for same time period
Outcomes	PPA at 12 months Validation: cotinine and carboxyhaemoglobin in a subsample of participants Adverse events: not reported
Notes	Funding and conflicts of interest not reported
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not stated
Allocation concealment (selection bias)	Unclear risk	Quote: "subjects were randomised"
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Quote: "in a double‐blind way"; blinding was broken at 3 months
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Losses evident in Tables II and IV