The Boston Children’s Hospital z-score system is based on data gathered over the past 12 years on normal children, using methods described in references 1 & 2. The height, weight, and BMI regressions are based on the downloadable files available from the CDC and WHO. The echocardiographic z-scores are periodically updated and new regressions are made available and deployed in this system as they become available.

1. Sluysmans T, Colan SD. Structural measurements and adjustment for growth. In: Lai WW, Cohen MS, Geva T, Mertens L, editors. Echocardiography in Pediatric and Congenital Heart Disease. Wiley-Blackwell, West Sussex, UK, 2009. Chapter 5.
2. Colan SD. Normal echocardiographic values for cardiovascular structures. In: Lai WW, Cohen MS, Geva T, Mertens L, editors. Echocardiography in Pediatric and Congenital Heart Disease. Wiley-Blackwell, West Sussex, UK, 2009. Appendix 1, pp 765-785.