Ulbricht 2014.

Methods	Country: Germany Setting: community (home and telephone) Type: RCT
Participants	917 households with parents of children younger than 4 years of age, where at least 1 parent was a smoker
Interventions	Intervention: 15 to 30‐minute in‐person behavioural change counselling session, a computer‐generated feedback letter (including the child's urine cotinine level), and a 5‐ to 15‐minute phone counselling session Control: received the same leaflet as the intervention group about the adverse effects of ETS on children. A letter containing information about the child urine cotinine level at baseline and 12 months later was sent after the 12‐month follow‐up assessment.
Outcomes	Child exposure: child urine cotinine and self‐reported SHS exposure, smoking status, and home smoking ban Target behavioural change: home smoking ban
Type of intervention	Community‐based
Notes	Conflict of interest: none declared Source of funding: German Cancer AID (Deutsche Krebshilfe, grant no. 107539) and DZHK (German Centre for Cardiovascular Research), partner site Greifswald, Germany (grant no. 81/Z540100152)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Not specified
Allocation concealment (selection bias)	Low risk	Screening team blinded to allocation and separate from intervention team
Incomplete outcome data (attrition bias) All outcomes	Low risk	89.7% follow‐up in intervention group; 96.4% follow‐up in control group
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Objective biological measure, although assessors of baseline and 12‐month follow up data were not blind to study group assignment