title: Evidence for the validity of the modified dynamic gait index across diagnostic groups.
abstract: BACKGROUND
  The modified Dynamic Gait Index (mDGI) measures the capacity to adapt gait to complex tasks utilizing 8 tasks and 3 facets of performance. The measurement stability of the mDGI in specific diagnostic groups is unknown.
  
  
  OBJECTIVE
  This study examined the psychometric properties of the mDGI in 5 diagnostic groups.
  
  
  METHODS
  This was a cross-sectional, descriptive study.
  
  
  METHODS
  A total of 794 participants were included in the study: 140 controls, 239 with stroke, 140 with vestibular dysfunction, 100 with traumatic brain injury, 91 with gait abnormality, and 84 with Parkinson disease. Differential item functioning analysis was used to examine the comparability of scores across diagnoses. Internal consistency was computed using Cronbach alpha. Factor analysis was used to examine the factor loadings for the 3 performance facet scores. Minimal detectable change at the 95% confidence level (MDC95%) was calculated for each of the groups.
  
  
  RESULTS
  Less than 5% of comparisons demonstrated moderate to large differential item functioning, suggesting that item scores had the same order of difficulty for individuals in all 5 diagnostic groups. For all 5 patient groups, 3 factors had eigenvalues >1.0 and explained 80% of the variability in scores, supporting the importance of characterizing mobility performance with respect to time, level of assistance, and gait pattern.
  
  
  CONCLUSIONS
  There were uneven sample sizes in the 6 groups.
  
  
  CONCLUSIONS
  The strength of the psychometric properties of the mDGI across the 5 diagnostic groups further supports the validity and usefulness of scores for clinical and research purposes. In addition, the meaning of a score from the mDGI, regardless of whether at the task, performance facet, or total score level, was comparable across the 5 diagnostic groups, suggesting that the mDGI measured mobility function independent of medical diagnosis.
authors.affiliation: P.N. Matsuda, PT, PhD, DPT, Department of Rehabilitation Medicine, Division of Physical Therapy, University of Washington, 1959 NE Pacific St, Box 356490, Seattle, WA 98195 (USA). pmatsuda@u.washington.edu.
authors.forename: Patricia Noritake
authors.initials: PN
authors.lastname: Matsuda
authors.affiliation: C.S. Taylor, PhD, College of Education, University of Washington.
authors.forename: Catherine S
authors.initials: CS
authors.lastname: Taylor
authors.affiliation: A. Shumway-Cook, PT, PhD, FAPTA, Department of Rehabilitation Medicine, Division of Physical Therapy, University of Washington.
authors.forename: Anne
authors.initials: A
authors.lastname: Shumway-Cook
mesh_terms: D000222:Adaptation, Physiological; D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001930:Brain Injuries / Q000503:physiopathology; D003430:Cross-Sectional Studies; D003953:Diagnosis-Related Groups; D005260:Female; D005684:Gait / Q000502:physiology*; D020233:Gait Disorders, Neurologic / Q000503:physiopathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D051346:Mobility Limitation; D010300:Parkinson Disease / Q000503:physiopathology; D011594:Psychometrics; D020521:Stroke / Q000503:physiopathology; D015837:Vestibular Diseases / Q000503:physiopathology; D016138:Walking / Q000502:physiology*; D055815:Young Adult