Home blood pressure monitoring in children: how many measurements are needed?

Objective: To investigate the minimum schedule of blood pressure (BP) measurements necessary to provide a reliable assessment of home BP (HBP) in children and adolescents.

Methods: Subjects aged 6-18 years referred for elevated BP were assessed with HBP monitoring (6 workdays, duplicate morning and evening measurements) and 24-h ambulatory BP monitoring (ABP). Criteria for HBP reliability were its reproducibility (test-retest correlations and SD of differences (SDDs) between repeated measurements), its stability (average home BP of an increasing number of readings and its SD), and its relationship with ABP.

Results: Data from 100 subjects were analyzed (mean age 13 +/- 2.8 (SD) years, 61 boys). The reproducibility of 3-day HBP (r 0.88/0.79, SDDs 5.1/4.9, systolic/diastolic) was superior to that of a single (r 0.79/0.65, SDDs 7.6/7.1) or 2-day HBP (r 0.85/0.72, SDDs 6.1/5.4). By averaging up to 12 readings (3 days), there was a progressive decline in average HBP, with no further decline thereafter. The SD of average HBP was also progressively reduced, with little change after day 3. The association of HBP with ABP was improved by averaging more readings up to 12, with no further improvement when more readings were averaged. The exclusion of first-day measurements slightly increased the SD of average HBP and weakened the correlation with ABP, probably due to reduced number of readings.

Conclusions: In children and adolescents, 3-day monitoring with duplicate morning and evening measurements appears to be the minimum schedule for the reliable assessment of HBP.