Assessment of the Performance of a Modified Motor Scale as Applied to Juvenile Onset Huntington's Disease

Mike C. Horton, Peggy Nopoulos, Martha Nance, G. Bernhard Landwehrmyer, Roger A. Barker, Ferdinando Squitieri, Jean Marc Burgunder, Oliver Quarrell

Research output: Contribution to journalArticlepeer-review


Background: Huntington's disease can present at almost any age but traditionally, those with an onset =20 years are described as having juvenile onset Huntington's disease (JOHD). They are more likely to have bradykinesia and dystonia earlier in the course of the disease. The Total Motor Score of the Unified Huntington's Disease Rating Scale (UHDRS-TMS) is often used as the principal outcome measure in clinical trials. Objective: To identify a motor scale more suitable for JOHD patients. Methods: A working group reviewed the UHDRS-TMS and modified it by adding four further assessment items. Rasch analysis was used to study the performance of the modified scale in 95 patients with a mean age of 19.4 (SD 6.6) years. Results: The initial analysis showed a significant overall misfit to the Rasch model and a number of individual items displayed poor measurement properties: all items relating to chorea displayed significant misfit due to under-discrimination. Additionally, a number of items displayed disordered response category thresholds, and a large amount of dependency was present within the item set (96 out of 741 pairwise differences = 13%). An iterative process of scale re-structuring and evaluation was then undertaken, with a view to eliminating the largest sources of misfit and generating a set of items that would conform to Rasch model expectations.

Original languageEnglish
Pages (from-to)181-193
Number of pages13
JournalJournal of Huntington's disease
Issue number2
Publication statusPublished - Jan 1 2019

ASJC Scopus subject areas

  • Clinical Neurology
  • Cellular and Molecular Neuroscience


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