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(Hypertension. 2000;35:e8.)
© 2000 American Heart Association, Inc.

Hypertension Electronic Pages

Ambulatory Blood Pressure: Normality and Comparison With Other Measurements

Jan A. Staessen, MD, PhD

Study Coordinating Center Hypertension Unit, University of Leuven, Leuven, Belgium

Eoin T. O’Brien, MD, PhD

Blood Pressure Unit Beaumont Hospital, Dublin, Ireland

	Introduction

 
To the Editor:

Dr. Schettini and colleagues¹ recently proposed that ambulatory blood pressure measurements are within the normotensive range if the 24-hour average is <125 mm Hg systolic and 80 mm Hg diastolic and if the daytime averages are <129 mm Hg and 84 mm Hg, respectively. These investigators also stated that more elevated limits of the ambulatory measurements would yield an artificially high prevalence of white coat hypertension.¹ However, the opposite is true: higher thresholds for ambulatory blood pressure measurement would be associated with a lower prevalence of white coat hypertension.²

Schettini and colleagues determined normal ambulatory blood pressure limits as those that best correlated with 140/90 mm Hg on clinic measurement, using linear regression analysis. Several problems arise:

1. The regression line provides the point estimate for predicting the population mean of the ambulatory blood pressure at any given level of clinic pressure. However, reference values should not be based on a predicted population mean but on the upper 95% confidence boundary around the regression line for predicting the ambulatory blood pressure in individual subjects.³ This interval is much wider (Figure 1) than that for predicting the population mean.³

View larger version (28K): [in this window] [in a new window]   Figure 1. Regression line relating 24-hour systolic pressure to systolic pressure at home in 1057 subjects. For clarity, the plot depicts only the results from home pressure measurements ranging from 110 to 170 mm Hg, but all data were used to calculate the regression line. The 95% confidence interval for the prediction of the mean 24-hour systolic pressure at a . . . [Full Text of this Article]

Edgardo Sandoya, MD; Fernando Nieto, MD; Carlos Schettini, MD; Manuel Bianchi, MD; Hugo Senra, MD

The Hypertension Working Group, Departamento de Cardiología, Asociación Española Primera de Socorros Mutuos, Montevideo, Uruguay