A SHORTENED VERSION OF THE MOTOR SECTION OF THE UNIFIED HUNTINGTONS-DISEASE RATING-SCALE

Objective assessment of clinical findings of patients with Huntington' s disease (HD) is necessary for an evaluation of the individual progre ssion of the disease and the effect of therapy, and it requires specif ic assessment scales. The Unified Huntington's Disease Rating Scale (U HDRS) is an overall scale to assess clinical performance and functiona l capacity. In the course of carrying out studies in HD, several items in the motor function section were found to be difficult to score, ha d high cognitive loading, and appeared to be redundant. The objective of this study was to shorten the motor section of the UHDRS to the sma llest number of items, without loss of internal consistency, while sti ll assessing the important clinical features of HD. Shortening the tot al motor score of the UHDRS was carried out on the UHDRS data set of t he Leiden University Hospital using four methods. The first two method s employed principal-component analysis with Varimax rotation. Strongl y interrelated test items were uncovered, resulting in a reduction of test items to a smaller set. The third method reduced items so that th e internal consistency (Cronbach's alpha) was maximal. The fourth meth od omitted items subjectively. The results of the Dutch data set were validated on follow-up data and on a data set from the University of R ochester Medical Center, New York. This study determined that the numb er of items in the motor function section could be reduced from 31 to 15. The reduced set maintains the relationships between the motor and other sections of the UHDRS and still assesses the major clinical feat ures of HD.