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Parkinson’s Disease
Volume 2012 (2012), Article ID 719167, 10 pages
http://dx.doi.org/10.1155/2012/719167
Research Article

Confirmatory Factor Analysis of the Motor Unified Parkinson’s Disease Rating Scale

1UCLA Department of Neurology, Box 951769, C109 RNRC, Los Angeles, CA 90095-1769, USA
2VA Greater Los Angeles Healthcare System, Parkinson’s Disease Research, Education and Clinical Center, Los Angeles, CA 90073, USA
3UCLA Division of General Internal Medicine and Health Services Research, Department of Medicine, Los Angeles, CA 90095, USA
4UCLA School of Public Health, Los Angeles, CA 90095-1772, USA
5RAND, Santa Monica, CA 90407, USA
6Department of Neurology, Harbor-UCLA Medical Center, Torrance, CA 90502, USA

Received 19 April 2012; Revised 5 July 2012; Accepted 25 July 2012

Academic Editor: E. D. Louis

Copyright © 2012 Stefanie D. Vassar et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

The motor examination section of the unified Parkinson’s disease rating scale (UPDRS) is widely used in research but few studies have examined whether subscales exist that tap relatively distinct motor abnormalities. We analyzed data from 193 persons enrolled in a population-based study in Central California. Patients were examined after overnight PD medication washout (“OFF” state) and approximately one hour after taking medication (“ON” state). We performed confirmatory factor analysis of the UPDRS for OFF and ON state examinations; correlations, reliability, and relative validity of resulting subscales were evaluated. A model with five factors (gait/posture, tremor, rigidity, bradykinesia affecting the left extremities, bradykinesia affecting the right extremities) fit the data well, with similar results for OFF and ON states. Internal consistency reliability coefficients were 0.90 or higher for all subscales. The gait/posture subscale most strongly discriminated across levels of patient reported PD symptom severity and of how PD affects them on a daily basis. Compared to the right sided bradykinesia subscale, the left sided bradykinesia subscale had higher discrimination across levels of self-reported PD symptom severity and functional impairment. This supports motor UPDRS containing multiple subscales that can be analyzed separately and provide information distinct from the total score that may be useful in clinical studies.