Spinal muscular atrophy functional composite score: A functional measure in spinal muscular atrophy

Muscle Nerve. 2015 Dec;52(6):942-7. doi: 10.1002/mus.24670. Epub 2015 Oct 10.


Introduction: With clinical trials underway, our objective was to construct a composite score of global function that could discriminate among people with spinal muscular atrophy (SMA).

Methods: Data were collected from 126 participants with SMA types 2 and 3. Scores from the Hammersmith Functional Motor Scale-Expanded and Upper Limb Module were expressed as a percentage of the maximum score and 6-minute walk test as percent of predicted normal distance. A principal component analysis was performed on the correlation matrix for the 3 percentage scores.

Results: The first principal component yielded a composite score with approximately equal weighting of the 3 components and accounted for 82% of the total variability. The SMA functional composite score, an unweighted average of the 3 individual percentage scores, correlated almost perfectly with the first principal component.

Conclusions: This combination of measures broadens the spectrum of ability that can be quantified in type 2 and 3 SMA patients.

Keywords: SMA; clinical trial; composite score; motor function; outcome measure; spinal muscular atrophy.

MeSH terms

  • Adolescent
  • Child
  • Child, Preschool
  • Female
  • Humans
  • Male
  • Movement / physiology
  • Muscular Atrophy, Spinal / diagnosis*
  • Muscular Atrophy, Spinal / physiopathology*
  • Principal Component Analysis
  • Prospective Studies
  • Severity of Illness Index*
  • Upper Extremity / physiopathology
  • Walking / physiology
  • Young Adult