Ambulatory blood pressure monitoring: mean blood pressure and blood pressure load

Ambulatory blood pressure monitoring (ABPM) is commonly used to diagnose pediatric hypertension. Using ABPM, hypertension is usually defined as a mean BP greater than the 95th percentile for height. A BP load > 30% (% of BP readings greater than the 95th percentile) is also used for the diagnosis of hypertension. The objective of this study was to determine the agreement between mean BP greater than the 95th percentile and 30% BP load for the diagnosis of hypertension using ABPM. All ABPM records (n =1,009) of patients referred for hypertension to a pediatric center were retrieved. Scans were excluded if: age was > 19 and height < 115 cm or > 185 cm. Mean BP and BP loads were calculated for 728 scans. Agreement between mean BP greater than the 95th percentile for height and various BP loads were calculated using the kappa coefficient. The kappa coefficient of agreement between mean BP greater than the 95th percentile and 30% BP load was 0.56 and 0.57 for daytime systolic and diastolic BP, respectively. The agreement between mean night-time BP greater than the 95th percentile and 30% BP load was 0.70 and 0.66 for systolic and diastolic BP, respectively. Agreement between mean BP greater than the 95th percentile and 30% BP load is only moderate to good. Maximum agreement between mean BP greater than the 95th percentile and BP load is achieved at 50% BP load.