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Original Contribution
January 2010

The Clinically Important Difference on the Unified Parkinson's Disease Rating Scale

Author Affiliations

Author Affiliations: Departments of Neurology (Drs Shulman, Anderson, Fishman, Reich, and Weiner), Epidemiology and Preventive Medicine (Dr Gruber-Baldini), and Psychiatry (Dr Anderson), University of Maryland School of Medicine, Baltimore.

Arch Neurol. 2010;67(1):64-70. doi:10.1001/archneurol.2009.295

Objective  To determine the estimates of minimal, moderate, and large clinically important differences (CIDs) for the Unified Parkinson's Disease Rating Scale (UPDRS).

Design  Cross-sectional analysis of the CIDs for UPDRS total and motor scores was performed on patients with Parkinson disease (PD) using distribution- and anchor-based approaches based on the following 3 external standards: disability (10% on the Schwab and England Activities of Daily Living Scale), disease stage (1 stage on the Hoehn and Yahr Scale), and quality of life (1 SD on the 12-Item Short Form Health Survey).

Setting  University of Maryland Parkinson Disease and Movement Disorders Center,

Patients  Six hundred fifty-three patients with PD.

Results  A minimal CID was 2.3 to 2.7 points on the UPDRS motor score and 4.1 to 4.5 on the UPDRS total score. A moderate CID was 4.5 to 6.7 points on the UPDRS motor score and 8.5 to 10.3 on the UPDRS total score. A large CID was 10.7 to 10.8 points on the UPDRS motor score and 16.4 to 17.8 on the UPDRS total score.

Conclusions  Concordance among multiple approaches of analysis based on subjective and objective data show that reasonable estimates for the CID on the UPDRS motor score are 2.5 points for minimal, 5.2 for moderate, and 10.8 for large CIDs. Estimates for the UPDRS total score are 4.3 points for minimal, 9.1 for moderate, and 17.1 for large CIDs. These estimates will assist in determining clinically meaningful changes in PD progression and response to therapeutic interventions.