Advantages of a modified scoring method for the Rush Video-Based Tic Rating Scale.

Previously, we published a video-based objective rating scale of tics that met reliability and validity criteria for measurement of five domains of tic disability. In the original form, the scale's metric properties did not permit internal comparison of each of the five domains of impairment and did not provide a total score for use as a primary outcome measure. In this study, we retained the original scale and videotape protocol but tested whether a modified scoring system corrected these limitations. The new scoring method rated assigned tic data to ratings of 0-4 on five disability categories: number of body areas, frequency of motor tics, frequency of phonic tics, severity of motor tics, and severity of phonic tics. The sums of these ratings yielded a total score of overall tic disability (0-20). In a series of 31 patients with Gilles de la Tourette syndrome, we assessed Spearman correlation coefficients for the old and new scoring systems as well as the correlation of the new ratings with the objectively derived sections of the Yale Global Tic Severity Scale (YGTSS), another valid and reliable scale used in clinical practice and research. For each domain, the rank order for the scores on the original scale was well retained in the new scores. Likewise, for each domain, ranking with the new scoring system correlated well with scores on the comparable objective item from the YGTSS. The new total score accurately captured the rank order of the combined five domains from the original scale and correlated well with the total objective motor plus phonic tic score from the YGTSS and the YGTSS Tourette Syndrome Overall Impairment Rating. These data demonstrate that the modified videotape-based scoring system retains the essential information gathered in the original Rush scale. The modification provides comparisons among the five assessed domains and a total objectively based disability score that can be used as a single outcome measure for assessing tic disability.