The Unified Dyskinesia Rating Scale: Presentation and clinimetric profile

Abstract

We developed and tested a rating scale aimed to capture the essential features of dyskinesia in Parkinson's disease (PD). Although several scales assess selected attributes of PD-dyskinesias, no comprehensive rating tool exists. Available rating scales were evaluated by the investigators and patient focus groups. Modifications were finalized into the Unified Dyskinesia Rating Scale (UDysRS). The UDysRS has four parts: I: Historical Disability (patient perceptions) of On-Dyskinesia impact (maximum 44 points); II: Historical Disability (patient perceptions) of Off-Dystonia impact (maximum 16 points); III: Objective Impairment (dyskinesia severity, anatomical distribution over seven body regions, and type (choreic or dystonic) based on four activities observed or video-recorded (28 points); IV: Objective Disability based on Part III activities (maximum 16 points). For clinimetric testing, 70 PD patients with all severities of dyskinesia were interviewed and videotaped. Twenty movement disorder experts rated the videotapes with the UDysRS. Internal consistency was examined with Cronbach's alpha. Inter- and intra-rater reliability was evaluated with generalized weighted and nonweighted Kappa coefficients, and intraclass correlation coefficients. Both subjective (Sections I and II) and objective (Sections III and IV) demonstrated high internal consistency (alpha: 0.915, 0.971). Interrater reliability for the objective sections was acceptable for all items and likewise for intrarater reliability except for right leg. Reliable factor structures were found for both subjective (six factors) and objective sections (five factors). The UDysRS is a clinimetrically sound rating scale for dyskinesia in PD, demonstrating acceptable levels of internal consistency and inter- and intra-rater reliability. Testing scale responsivity to treatment interventions is planned.