Influence of blood pressure level and age on within-visit blood pressure variability in children and adolescents.

Blood pressure (BP) is variable in children and this could affect BP assessment, but the magnitude of within-visit BP variability (BPV) over consecutive measurements has never been investigated. This study aimed to determine the direction and magnitude of, and factors affecting, within-visit BPV in children and adolescents. BP was recorded among 3047 children (aged 12 years [95%CI 12, 13], males 52%) from the 2011-2013 Australian Health Survey. BPV was defined as the absolute difference (∆SBPABS ) between the first (SBP1) and second systolic BP (SBP2) and the overall variability in three measures when available (SBPV). On average, ∆SBPABS was 6.7 mmHg (95%CI 6.3, 7.0) and SBPV was 8.2% (95%CI 7.8, 8.6). ∆SBPABS was greater with higher BP levels but lower with older age. From first to second measurements, SBP decreased in 58% (95%CI 56, 60), did not change in 10% (95%CI 9, 12), and increased in 32% (95%CI 29, 34) of the population.

CONCLUSIONS: BP is highly variable in children and adolescents, with the magnitude of variability being associated with both age and BP level. SBP increases on repeat measurement in a substantial proportion of the population. The optimal protocol of BP assessment to address this increased BPV needs to be determined. What is Known: • Diagnosis of elevated blood pressure (BP) is based on strict probabilistic criteria, the difference between the 90th (pre-hypertension) and 95th (hypertension) percentiles only being 3-4 mmHg. • BP variability could affect BP classification among children and adolescents. What is New: • The magnitude of BP change among children and adolescents is highly affected by BP level and age. • BP does not always drop on consecutive measurements, and evidence-based BP assessment protocols should be established to avoid misdiagnosis of hypertension.