Prevalence of white coat effect in treated hypertensive patients in the community.

Patients receiving drug therapy for hypertension in the tertiary care setting frequently exhibit higher office readings compared to ambulatory blood pressure values (white coat effect). In this study, the prevalence of a white coat effect was determined in an unselected population of 147 hypertensive patients receiving treatment from their family physicians in the community. The proportion of patients with a white coat effect (defined as office - ambulatory blood pressure > or = 20/10 mm Hg) was significantly (P < .001) higher when based upon the family physician's routine blood pressure readings (91/147), compared to special readings taken by the family physician for the study (54/147) or readings taken by a research nurse (30/147). There was a higher correlation (P < .05) between the ambulatory systolic blood pressure and the nurse's readings (r = 0.62) or special physician's readings (r = 0.55) v the routine physician's readings (r = 0.34). Left ventricular mass index as measured by echocardiography correlated (P < .01) with the special physician (r = 0.27), nurse (r = 0.23), and ambulatory systolic blood pressure readings (r = 0.24), but not with the routine physician's readings (r = 0.06). A white coat effect is frequently present in treated hypertensive patients when blood pressure is recorded by family physicians in routine clinical practice.