title: Optimising mobility outcome measures in Huntington's disease.
abstract: BACKGROUND
  Many of the performance-based mobility measures that are currently used in Huntington's disease (HD) were developed for assessment in other neurological conditions such as stroke.
  
  
  OBJECTIVE
  We aimed to assess the individual item-response of commonly used performance-based mobility measures, with a view to optimizing the scales for specific application in Huntington's Disease (HD).
  
  
  METHODS
  Data from a larger multicentre, observational study were used. Seventy-five people with HD (11 pre-manifest & 64 manifest) were assessed on the Six-Minute Walk Test, 10-Meter Walk Test, Timed "Up & Go" Test (TUG), Berg Balance Scale (BBS), Physical Performance Test (PPT), Four Square Step Test, and Tinetti Mobility Test (TMT). The Unified Huntington's Disease Rating Scale (UHDRS) Total Motor Score, Functional Assessment Scale and Total Functional Capacity scores were recorded, alongside cognitive measures. Standard regression analysis was used to assess predictive validity. Individual item responses were investigated using a sequence of approaches to allow for gradual removal of items and the subsequent creation of shortened versions. Psychometric properties (reliability and discriminant ability) of the shortened scales were assessed.
  
  
  RESULTS
  TUG (β 0.46, CI 0.20-3.47), BBS (β -0.35, CI -2.10-0.14), and TMT (β -0.45, CI -3.14-0.64) were good disease-specific mobility measures. PPT was the best measure of functional performance (β 0.42, CI 0.00-0.43 for TFC & β 0.57 CI 0.15-0.81 for FAS). Shortened versions of BBS and TMT were developed based on item analysis. The resultant BBS and TMT shortened scales were reliable for use in manifest HD. ROC analysis showed that shortened scales were able to discriminate between manifest and pre-manifest disease states.
  
  
  CONCLUSIONS
  Our data suggests that the PPT is appropriate as a general measure of function in individuals with HD, and we have identified shortened versions of the BBS and TMT that measure the unique gait and balance impairments in HD. These scales, alongside the TUG, may therefore be important measures to consider in future clinical trials.
authors: School of Healthcare Sciences, Cardiff University, Cardiff, UK.
authors: Monica
authors: M
authors: Busse
authors: School of Healthcare Sciences, Cardiff University, Cardiff, UK.
authors: Lori
authors: L
authors: Quinn
authors: Department of Rehabilitation Sciences, Faculty of Applied Medical Sciences, Jordan University of Science and Technology, Irbid, Jordan.
authors: Hanan
authors: H
authors: Khalil
authors: Institute of Translation, Innovation, Methodology & Engagement Cardiff University School of Medicine, Cardiff, UK.
authors: Kirsten
authors: K
authors: McEwan
mesh_terms: D004185:Disability Evaluation; D005080:Exercise Test; D006816:Huntington Disease / Q000503:physiopathology* / Q000628:therapy*; D009043:Motor Activity / Q000502:physiology*; D017063:Outcome Assessment, Health Care; D026741:Physical Therapy Modalities / Q000592:standards*; D011446:Prospective Studies; D011594:Psychometrics; D011597:Psychomotor Performance / Q000502:physiology*; D012372:ROC Curve; D015203:Reproducibility of Results; D016138:Walking
keywords: Huntington's Disease; function; mobility; outcome measures