WHO height charts can be safely substituted when calculating BP Z-scores in a North American clinic setting

Area of Science:

• Pediatric cardiology
• Public health
• Growth assessment

Background:

• North American blood pressure (BP) Z-scores often rely on US Centers for Disease Control (CDC) height charts.
• The Public Health Agency of Canada has adopted World Health Organization (WHO) growth charts.
• Discrepancies between CDC and WHO height charts may impact BP Z-score accuracy, especially in young children.

Purpose of the Study:

• To evaluate the impact of substituting WHO height Z-scores for CDC height Z-scores on BP Z-scores in children.
• To assess the accuracy of BP Z-scores calculated using WHO height data in a large pediatric cohort.

Main Methods:

• Analysis of real-world BP measurements from over 22,000 children aged 2 to 18 years.
• Comparison of BP Z-scores derived from WHO and CDC height charts.
• Application of Bland-Altman limits of agreement (LOA) to quantify measurement agreement.

Main Results:

• WHO height Z-scores were systematically lower in toddlers (2-5 years) compared to CDC scores (bias = -0.30 SD).
• Systolic BP Z-scores showed excellent agreement between the two height chart methods (bias = 0.06 SD).
• Errors were smaller for older children and diastolic BP, with good agreement across all BP ranges (hypotensive, normotensive, hypertensive).

Conclusions:

• Clinicians can confidently use World Health Organization (WHO) height charts for calculating blood pressure (BP) Z-scores and percentiles.
• The substitution of WHO for CDC height data does not significantly compromise BP Z-score accuracy in children.
• This supports the integration of WHO growth charts for pediatric BP assessment in North America.