Validation of US cerebral palsy growth charts using a UK cohort

Abstract

Aim: Growth charts for cerebral palsy (CP) have been constructed using data for 24 920 Californian patients, covering ages 2 to 20 years, with separate charts for the five severity levels of the Gross Motor Function Classification System (GMFCS). Our aim was to test how the data for British children with CP fit these charts, compared with conventional local charts. Method: US CP growth reference was reanalysed using the lambda-mu-sigma (LMS) method to allow calculation of standard deviation z-scores. Growth data for 195 children with CP in Glasgow, UK, were retrieved and converted to z-scores using the CP reference as well as the combined World Health Organization and UK 1990 growth reference (UK-WHO). Results: Compared to the UK-WHO reference, measurements diverged progressively with increasing severity, with mean height for GMFCS level V being close to the second UK-WHO centile. Compared with the CP reference, mean height and weight z-scores were between the 50th and 75th centiles for all severity levels, while body mass index was just below the 50th centile. Interpretation: British children with severe CP seem relatively very small when their growth data are plotted on non-CP charts, but their data for weight and body mass index fit well to US CP charts and reasonably well for height. The LMS look-up tables will make it possible to calculate z-scores and produce charts in local formats.