DIFFERENCE BETWEEN CLINIC AND DAYTIME BLOOD-PRESSURE IS NOT A MEASUREOF THE WHITE COAT EFFECT

The purpose of the present study was to evaluate whether the differenc e between blood pressure measured in the clinic or physician's office and the average daytime blood pressure accurately reflects the blood p ressure response of the patient to the physician (''white coat effect' ' or ''white coat hypertension''). We studied 28 hypertensive outpatie nts (mean age, 41.8+/-11.2 years; age range, 21 to 64 years) of 35 con secutive patients attending our hypertension clinic, in whom (1) conti nuous noninvasive finger blood pressure was recorded before and during the visit, (2) blood pressure was measured according to the Riva-Rocc i-Korotkoff method (mercury sphygmomanometer) with the patient in the supine position, and (3) daytime ambulatory blood pressure was monitor ed with a SpaceLabs 90207 device. The peak blood pressure increase rec orded directly during the visit was compared with the difference betwe en clinic and daytime average ambulatory blood pressures. Compared wit h previsit values, peak increases in finger systolic and diastolic blo od pressures during the visit to the clinic were 38.2+/-3.1 and 20.7+/ -1.6 mm Hg, respectively (mean+/-SEM, P<.01 for both). Daytime average systolic and diastolic blood pressures were 135.5+/-2.5 and 89.2+/-1. 9 mm Hg, with both lower than the corresponding clinic blood pressure values (146.6+/-3.6 and 94.9+/-2.2 mm Hg, P<.01), These differences, h owever, were <30% of the peak finger blood pressure increases during t he physician's visit, to which these increases showed no relation. Alt hough the visit to the physician's office was associated with tachycar dia (9.0+/-1.6 bpm, P<.01), there was no difference between clinic and daytime average heart rates. These data indicate that the clinic-dayt ime average blood pressure difference does not reflect the alerting re action and the pressure response elicited by the physician's visit and thus is not a reliable measure of the white coat effect.