Rasch analysis of clinical outcome measures in spinal muscular atrophy

Stefan J. Cano, Anna Mayhew, Allan M. Glanzman, Kristin J. Krosschell, Kathryn J. Swoboda, Marion Main, Birgit F. Steffensen, Carole Bérard, Françoise Girardot, Christine A M Payan, Eugenio Mercuri, Elena Mazzone, Bakri Elsheikh, Julaine Florence, Linda S. Hynan, Susan T. Iannaccone, Leslie L. Nelson, Shree Pandya, Michael Rose, Charles ScottReza Sadjadi, Mackensie A. Yore, Cynthia Joyce, John T. Kissel

Research output: Contribution to journalArticlepeer-review

59 Scopus citations


Introduction: Trial design for SMA depends on meaningful rating scales to assess outcomes. In this study Rasch methodology was applied to 9 motor scales in spinal muscular atrophy (SMA). Methods: Data from all 3 SMA types were provided by research groups for 9 commonly used scales. Rasch methodology assessed the ordering of response option thresholds, tests of fit, spread of item locations, residual correlations, and person separation index. Results: Each scale had good reliability. However, several issues impacting scale validity were identified, including the extent that items defined clinically meaningful constructs and how well each scale measured performance across the SMA spectrum. Conclusions: The sensitivity and potential utility of each SMA scale as outcome measures for trials could be improved by establishing clear definitions of what is measured, reconsidering items that misfit and items whose response categories have reversed thresholds, and adding new items at the extremes of scale ranges.

Original languageEnglish (US)
Pages (from-to)422-430
Number of pages9
JournalMuscle and Nerve
Issue number3
StatePublished - Mar 2014


  • Clinical trials
  • Motor neuron disease
  • Outcome measures
  • Rasch analysis
  • Spinal muscular atrophy

ASJC Scopus subject areas

  • Physiology
  • Clinical Neurology
  • Cellular and Molecular Neuroscience
  • Physiology (medical)


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