FACTOR STRUCTURE OF THE UNIFIED PARKINSONS-DISEASE RATING-SCALE - MOTOR EXAMINATION SECTION

The Unified Parkinson's Disease Rating Scale (UPDRS) is widely used to assess Parkinson's disease (PD) disability but its metric properties have not been extensively studied. We investigated the factor structur e and internal consistency of the Motor Examination section of the UPD RS in a sample of 294 consecutive patients with idiopathic PD who were assessed while in the ''on'' state. There was a high degree of intern al consistency. Factor analysis revealed six clinically distinct facto rs, three bradykinesia measures (axial/gait, right and left), one rigi dity measure, and two tremor measures (rest and postural). These facto rs accounted for 78% of the variance. Total Motor Examination scores a nd selected factors correlated well with other examiner-determined glo bal ratings of PD disability (Hoehn and Yahr stage and Schwab-England Activities of Daily Living score). These results suggest that the Moto r Examination section of the UPDRS provides a useful measure of PD fun ction as well as severity measures of six clinical disability domains.