Methods of consumer involvement in developing healthcare policy and research, clinical practice guidelines and patient information material -Cochrane

http://mrw.interscience.wiley.com/cochrane/clsysrev/articles/CD004563/frame.html

"Two studies, which compared using consumer interviewers with staff interviewers as data collectors for patient satisfaction surveys, found small differences in satisfaction survey results, with less favourable results obtained when consumers were the interviewers."