Unified Parkinson's disease rating scale characteristics and structure

Our purpose was to verify some basic aspects of validation of the Unified Parkinson's Disease Rating Scale (UPDRS). One hundred and sixtyseven Parkinson's disease (PD) patients were included. Group A (n=40) was simultaneously assessed by five raters who applied the UPDRS and other PD rating scales (PDRS). A set of timed tests, the Mini-Mental State Examination (MMSE), and the Hamilton Scale for Depression (HSD) were administered by an independent examiner. Group B (n = 127) was individually assessed through the UPDRS and the other PDRSs by one neurologist in four different hospitals. The UPDRS was administered in 16.95 ± 7.98 min. The internal consistency was high (Cronbach's alpha = 0.96). Nevertheless, the items related to depression, motivation/initiative, and tremor were scarcely consistent. The Interrater reliability was satisfactory (all the items had k > 0.40). There was a high correlation of the UPDRS with the Hoehn and Yahr staging (r_s = 0.71; p < 0.001) and some timed tests (finger tapping; arising from chair), but also with the MMSE and HSD (r_s = 0.53; r_s = 0.64; p < 0.001). The convergent validity with the other PDRS (Intermediate Scale and Schwab and England Scale) was very high (r_s = 0.76−0.96; p < 0.001). The factor analysis identified six factors that explained 59.6% of the variance. The dimension “tremor” showed a remarkable independence. The UPDRS is a multidimensional, reliable, and valid scale, with some inconveniences derived from its internal consistency, discriminant validity, and pragmatic application.