Validating the Rett Syndrome Gross Motor Scale

PLoS One. 2016 Jan 22;11(1):e0147555. doi: 10.1371/journal.pone.0147555. eCollection 2016.


Rett syndrome is a pervasive neurodevelopmental disorder associated with a pathogenic mutation on the MECP2 gene. Impaired movement is a fundamental component and the Rett Syndrome Gross Motor Scale was developed to measure gross motor abilities in this population. The current study investigated the validity and reliability of the Rett Syndrome Gross Motor Scale. Video data showing gross motor abilities supplemented with parent report data was collected for 255 girls and women registered with the Australian Rett Syndrome Database, and the factor structure and relationships between motor scores, age and genotype were investigated. Clinical assessment scores for 38 girls and women with Rett syndrome who attended the Danish Center for Rett Syndrome were used to assess consistency of measurement. Principal components analysis enabled the calculation of three factor scores: Sitting, Standing and Walking, and Challenge. Motor scores were poorer with increasing age and those with the p.Arg133Cys, p.Arg294* or p.Arg306Cys mutation achieved higher scores than those with a large deletion. The repeatability of clinical assessment was excellent (intraclass correlation coefficient for total score 0.99, 95% CI 0.93-0.98). The standard error of measurement for the total score was 2 points and we would be 95% confident that a change 4 points in the 45-point scale would be greater than within-subject measurement error. The Rett Syndrome Gross Motor Scale could be an appropriate measure of gross motor skills in clinical practice and clinical trials.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Australia
  • Child
  • Databases, Factual
  • Denmark
  • Female
  • Humans
  • Motor Skills*
  • Movement / physiology
  • Reproducibility of Results
  • Rett Syndrome / diagnosis*
  • Rett Syndrome / physiopathology
  • Severity of Illness Index
  • Young Adult

Grants and funding

Funding for this study has been received from the National Health and Medical Research Council project grant #303189 (HL) and #1004384 (HL, JD), program grant #572742 (HL), and a research fellowship #572568 (HL) ( The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.