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Rating scales for dystonia: A multicenter assessment



The evaluation of dystonia requires a reliable rating scale. The widely used Fahn-Marsden Scale (F-M) has not been sufficiently tested across multiple centers and investigators. The Dystonia Study Group developed the Unified Dystonia Rating Scale (UDRS) and a Global Dystonia Rating Scale (GDS) to serve as instruments to assess dystonia severity. In this study, 25 dystonia experts evaluated the UDRS, F-M, and GDS for internal consistency and reliability. One hundred dystonia patients were videotaped using a standardized videotape protocol. Each examiner rated 20 patients using the UDRS, F-M, and GDS in random order. The examiner then assessed each scale for ease of use. Statistical analysis used Cronbach's α, intraclass correlation coefficients (ICC), generalized weighted κ statistic, and Kendall's coefficient of concordance. The UDRS, F-M, and GDS showed excellent internal consistency (Cronbach's α 0.89–0.93) and good to excellent correlation among the raters (ICC range from 0.71–0.78). Inter-rater agreement was fair to excellent (Kendall's 0.54–0.87; κ 0.37–0.91) being lowest for eyes, jaw, face, and larynx. The modifying ratings (Duration in the UDRS and Provoking Factor in the F-M) showed less agreement than the motor severity ratings. Among scales, the total scores correlated (Pearson's r, 0.977–0.983). Overall, 74% of raters found the GDS the easiest to apply. The GDS with its simplicity and ease of application may be the most useful dystonia rating scale. © 2002 Movement Disorder Society