How representative are patients in general practice morbidity surveys?

This study examined differences arising from the sampling of patients from general practice and household surveys. When 25 general practitioners, who agreed to participate in one week morbidity survey in inner western Sydney, were compared with all general practitioners (192) identified in the area, they were not significantly different in terms of socio-demographic variables and practice details. When the demographic characteristics of a sample of patients at 539 encounters with the 25 participating general practitioners were compared with those of a sample of 500 patients identified from a household survey who had consulted with any general practitioner within 2 weeks of the interview, few differences were found. Few significant differences were found in the reasons for encounter and diagnoses treated as recalled by the patients of the two groups. No differences were found in management--specifically prescription, investigations and referral--or with respect to health status. This study suggests that sampling of patients from randomly selected general practitioners can produce useful representative samples for studies of morbidity even when doctor participation rates are as low as 29%.