Pediatric Echo Z-Score Calculator (BSA Normalized)

In pediatric cardiology, absolute measurements of cardiac structures are clinically insufficient due to somatic growth. A 12mm aortic root is normal for an infant but critical for a neonate. To assess pathology, measurements must be normalized against the patient's Body Surface Area (BSA) to generate a Z-score. The Z-score represents the number of standard deviations a measurement falls above or below the population mean for a child of that size.

This tool aggregates regression data from major multicenter studies, including the Boston Children's Hospital (Colan et al.) and Detroit (Pettersen et al.) datasets. It automatically computes BSA using the Haycock formula-widely considered the most accurate for infants-and applies the specific heteroscedastic regression models to output precise Z-scores. Scores falling outside the range of ±2 are flagged as statistically significant outliers.

First, Body Surface Area (BSA) is calculated using the Haycock formula:

The Z-score (Z) is derived by comparing the observed value (x) to the predicted mean (μ) and standard deviation (σ) for that BSA:

Note: Some datasets use log-transformation. In those cases, the calculation occurs in log-space before converting back or calculating the Z-score directly on the transformed variable.