Tracking and prediction of blood pressure in children.

A significant but weak correlation between an initial and a subsequent blood pressure measurement in the same patient has been found in several previous longitudinal studies of blood pressure in children. In the current study, single determinations of blood pressure, weight, and height were recorded in 142 children at 5.9 to 9.5 years of age and again 9 years later. Both examinations were performed in a schoolroom. Body size at the first examination was associated with body size 9 years later. A significant correlation was noted between initial and subsequent raw systolic blood pressures (r = 0.36 in boys and in girls; P less than 0.01). Correlations of systolic blood pressure based on percentiles for age and for height and weight were smaller but also statistically significant. Correlations involving diastolic blood pressure, with use of raw blood pressure measurements, were significant only for boys (r = 0.24, P less than 0.05). Correlations were not improved when indices of body size were used. Single blood pressure measurements obtained under the usual conditions in a schoolroom had only slightly weaker correlations with subsequent blood pressure determinations than those obtained in studies in which considerable care was taken to achieve more "basal" measurements. This degree of blood pressure correlation is insufficient to allow accurate prediction of subsequent blood pressure levels on the basis of a single casual blood pressure measurement in an individual child. This result was indicated by a wide 95% confidence interval for the predicted subsequent systolic blood pressure, even when sex, initial diastolic blood pressure, weight, and change in weight were considered.