Clark 1999.

Methods	RCT Risk of Bias: Moderate Allocation concealment: Clients interviewed by the client interviewers had been ill for a longer period than those interviewed by the staff members. Small number of interviewers (four at each of the two facilities). An interviewer effect could have been related to the personality of the interviewers rather than to the distinction client interviewer vs staff interviewer. Trial aim: To look for differences in data collected by consumers compared to data collected by health professionals in a patient satisfaction survey.
Participants	120 outpatient clients, aged 18 to 65 years who had a diagnosis of a major mental illness were randomly assigned to be interviewed by either a consumer or a professional about their satisfaction with services . Setting: Clarke Institute of Psychiatry and Queen Street Mental Health Centre in Toronto. Country: Canada.
Interventions	Type of process: Consumer involvement in research. The intervention group (60) was interviewed by consumers. The control group (60) was interviewed by professionals.
Outcomes	Interviewer effect measured by between‐group difference in level of patient satisfaction with case management and physicians' services, and between‐group difference in the number of extremely negative or positive responses.
Notes	Consumers were involved in research (patient satisfaction survey) as interviewers (data collectors).
Risk of bias
Bias	Authors' judgement	Support for judgement
Allocation concealment (selection bias)	Unclear risk	B ‐ Unclear