title: Rasch analysis of clinical outcome measures in spinal muscular atrophy.
abstract: BACKGROUND
  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.
authors.affiliation: Clinical Neurology Research Group, Room N13 ITTC Building, Peninsula College of Medicine and Dentistry, Tamar Science Park, Plymouth, United Kingdom.
authors.forename: Stefan J
authors.initials: SJ
authors.lastname: Cano
authors.forename: Anna
authors.initials: A
authors.lastname: Mayhew
authors.forename: Allan M
authors.initials: AM
authors.lastname: Glanzman
authors.forename: Kristin J
authors.initials: KJ
authors.lastname: Krosschell
authors.forename: Kathryn J
authors.initials: KJ
authors.lastname: Swoboda
authors.forename: Marion
authors.initials: M
authors.lastname: Main
authors.forename: Birgit F
authors.initials: BF
authors.lastname: Steffensen
authors.forename: Carole
authors.initials: C
authors.lastname: Bérard
authors.forename: Françoise
authors.initials: F
authors.lastname: Girardot
authors.forename: Christine A M
authors.initials: CA
authors.lastname: Payan
authors.forename: Eugenio
authors.initials: E
authors.lastname: Mercuri
authors.forename: Elena
authors.initials: E
authors.lastname: Mazzone
authors.forename: Bakri
authors.initials: B
authors.lastname: Elsheikh
authors.forename: Julaine
authors.initials: J
authors.lastname: Florence
authors.forename: Linda S
authors.initials: LS
authors.lastname: Hynan
authors.forename: Susan T
authors.initials: ST
authors.lastname: Iannaccone
authors.forename: Leslie L
authors.initials: LL
authors.lastname: Nelson
authors.forename: Shree
authors.initials: S
authors.lastname: Pandya
authors.forename: Michael
authors.initials: M
authors.lastname: Rose
authors.forename: Charles
authors.initials: C
authors.lastname: Scott
authors.forename: Reza
authors.initials: R
authors.lastname: Sadjadi
authors.forename: Mackensie A
authors.initials: MA
authors.lastname: Yore
authors.forename: Cynthia
authors.initials: C
authors.lastname: Joyce
authors.forename: John T
authors.initials: JT
authors.lastname: Kissel
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D016208:Databases, Factual / Q000706:statistics & numerical data; D004185:Disability Evaluation; D005260:Female; D006801:Humans; D007223:Infant; D008297:Male; D008875:Middle Aged; D009134:Muscular Atrophy, Spinal / Q000145:classification / Q000175:diagnosis* / Q000503:physiopathology*; D017063:Outcome Assessment, Health Care; D011594:Psychometrics; D015203:Reproducibility of Results; D055815:Young Adult
keywords: Rasch analysis; clinical trials; motor neuron disease; outcome measures; spinal muscular atrophy