The Unified Parkinson's Disease Rating Scale (UPDRS): status and recommendations

The Movement Disorder Society Task Force for Rating Scales for Parkinson's Disease prepared a critique of the Unified Parkinson's Disease Rating Scale (UPDRS). Strengths of the UPDRS include its wide utilization, its application across the clinical spectrum of PD, its nearly comprehensive coverage of motor symptoms, and its clinimetric properties, including reliability and validity. Weaknesses include several ambiguities in the written text, inadequate instructions for raters, some metric flaws, and the absence of screening questions on several important non-motor aspects of PD. The Task Force recommends that the MDS sponsor the development of a new version of the UPDRS and encourage efforts to establish its clinimetric properties, especially addressing the need to define a Minimal Clinically Relevant Difference and a Minimal Clinically Relevant Incremental Difference, as well as testing its correlation with the current UPDRS. If developed, the new scale should be culturally unbiased and be tested in different racial, gender, and age-groups. Future goals should include the definition of UPDRS scores with confidence intervals that correlate with clinically pertinent designations, "minimal," "mild," "moderate," and "severe" PD. Whereas the presence of non-motor components of PD can be identified with screening questions, a new version of the UPDRS should include an official appendix that includes other, more detailed, and optionally used scales to determine severity of these impairments.