Comparative responsiveness of Parkinson's disease scales to change over time.

The objective of the study is to examine the comparative responsiveness of outcome measures to assess progression over time in Parkinson's disease (PD). One hundred twenty-eight patients participating in a clinic-based naturalistic study of PD were assessed with the Hoehn and Yahr, UPDRS, MMSE, PDQ-39, PDQL, EQ-5D, and BDI scales at baseline and at 1 year. In addition, 82 patients in a community-based study of patients with PD who had completed self-rated Schwab and England, PDQ-39, EQ-5D, and BDI scales at baseline, were sent the same questionnaires at 1 and 4 years. Responsiveness was assessed using t-tests, standardised effect size, and standardised response mean. In both samples, the Hr-QoL measures were less responsive to change over time than the impairment and disability scales (Hoehn and Yahr, UPDRS, Schwab and England scales). In addition, in the clinic-based sample, Hoehn and Yahr and UPDRS ADL scale ("on") were more responsive to progression over time than UPDRS motor part and ADL part ("off"). Hr-QoL measures are less responsive to change over time than measures of impairment and disability. Although this suggests that these measures are less accurate in detecting subtle changes, it may also indicate that the multifactorial subjective assessment of Hr-QoL adapts to changes over time. Global assessment of overall impairment and disability (which incorporates motor and nonmotor features of PD), however, appeared relatively responsive to change over time in patients in a naturalistic setting.