Temporal stability of the Unified Dyskinesia Rating Scale

Background: The objective of this study was to establish temporal stability characteristics for objective components of the Unified Dyskinesia Rating Scale (UDysRS). The UDysRS has strong internal consistency and a reliable factor structure, but the important issue of temporal stability has not been established. Methods: Using intraclass correlation coefficient (ICC) analyses, we examined UDysRS temporal stability for the objective scale components (Part III and IV) over an 8-hour observation period. We assessed ICCs for the single centralized rater, the on-site raters, and the agreement between the single centralized rater and the on-site raters. Kappa statistic assessed agreement between the single centralized and on-site raters for clinical state (ON vs OFF). Results: For both the single centralized rater and the on-site raters, there was high temporal stability of the UDysRS Part III, Part IV, and Total Objective UDysRS in both ON and OFF states, with ICCs ranging from 0.822 (P<.0005) to 0.513 (P<.013). The agreement between the 2 rating techniques (centralized vs on-site) was significant for ON and OFF ratings of Part III, Part IV, and Total Objective UDysRS, ranging from 0.821 (P<.0005) to 0.703 (P<.0005). Conclusions: The UDysRS is highly stable for ON and OFF. Our data suggest that a single UDysRS evaluation for ON and for OFF states is highly representative of that state regardless of time. Likewise, if appropriate protocols need to assess dyskinesia in a field or community setting, the UDysRS can be filmed without an on-site rater and rated centrally with retained validity. (C) 2011 Movement Disorder Society