Methods	Cluster RCT, the hospital was the unit of randomisation.
Participants	Surgeons from 28 academic/community hospitals; Intervention: n=18 and Control: n= 10 Country: US Type of targeted behaviour: general management of a problem (breast cancer surgical care)
Interventions	Intervention Local Opinion Leaders + performance feedback Method of OL identification: Sociometric Proportion of Social Network that nominated OL: 50% Single OL or OL teams: single OL OL disseminated information: formal (grand rounds & dissemination of graphical material). Informal: NOT CLEAR OL frequency of involvement:UNCLEAR Control Performance feedback (distributing performance reports that contained data on the outcomes of interest)
Outcomes	Proportion of women who reported that their surgeons did not discuss surgical options prior to surgery for stage I or II breast cancer. Proportion of women who underwent breast conserving surgery
Notes
Risk of bias
Bias	Authors’ judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Pg.172/Col 2/Para 2 Hospitals in Minneapolis and St.Paul were assigned as clusters to separate treatment groups because crossover from one city to the other did not occur. Hospitals outside the metropolitan area and affiliated with a metropolitan hospital were assigned to the metropolitan hospital cluster, the without affiliations were randomly assigned to a hospital cluster. We randomly assigned a clusterof 18 hospitals to the opinion leader intervention and a cluster of 10 hospitals to the performance feedback group
Allocation concealment (selection bias)	Low risk	It was a cluster RCT, with the hospital as the unit of randomisation
Blinding (performance bias and detection bias) All outcomes	Unclear risk	Not mentioned in the paper.
Incomplete outcome data (attrition bias) All outcomes	Unclear risk	Not mentioned in the paper.
Selective reporting (reporting bias)	Unclear risk	Do not mention the outcomes of interest in the methods section
Other bias	Low risk
Similar baseline outcome measures?	Unclear risk	Not mentioned in the paper.
Similar baseline characteristics?	Low risk	p.173/Col2/Para2 The characteristics of patients treated at experimental and control hospitals were comparable
Protection against contamination?	Low risk	Randomisation was done at the hospital level.