Category: Pediatric Movement Disorders
Objective: The aim was to determine the minimal clinically important difference (MCID) on the Yale Global Tic Severity Scale (YGTSS), using the Clinical Global Impression of Tourette Syndrome Severity (CGI-TS-S) and Clinical Global Impression of Tourette Syndrome Improvement (CGI-TS-I) as anchors, in pediatric patients with Tourette syndrome (TS) receiving pharmacotherapy.
Background: Accurate assessment of treatment outcomes is essential for evidence-based clinical care. The MCID for an outcome of interest can be determined with an anchor-based approach, such as using the CGI-TS-S/CGI-TS-I as external criteria (anchors) to identify patients with perceptible improvement in TS severity and determine the corresponding change in YGTSS scores.
Method: The study included data from 2 trials of the investigational drug ecopipam (1 randomized controlled trial and its open-label extension). Receiver operating characteristic analysis determined the percentage improvement in YGTSS Total Tic Score (YGTSS-TTS) that distinguished patients with improvement from those with no change or worsening on the CGI-TS-S and CGI-TS-I. Spearman’s correlation, empirical cumulative distribution function, and probability distribution function analyses examined relationships between YGTSS-TTS and CGI-TS-S or CGI-TS-I.
Results: Overall, 133 patients were included (75.2% male; mean [SD] age, 12.7 [2.8] y); 63.2% had improvement on the CGI-TS-S; 78.2% on the CGI-TS-I. Percentage reduction in YGTSS scores that distinguished improvement from no change or worsening on the CGI-TS-S and CGI-TS-I ranged from 18.6% to 33.3% (AUC range, 0.71-0.81). Improvement on the YGTSS-TTS correlated with posttreatment CGI-TS-S (r=−0.65; P<0.001) and CGI-TS-I (r=−0.61; P<0.001) scores. The MCID for YGTSS-TTS was achieved by 67% and 62% with improvement on the CGI-TS-S and CGI-TS-I, respectively.
Conclusion: This analysis is the first to establish the MCID for YGTSS in a pediatric population with TS receiving pharmacotherapy. Whether using CGI-TS-S or CGI-TS-I as the anchor, a 25% reduction in YGTSS scores was an appropriate minimum threshold to define clinically meaningful improvement in this population. Results provide an objective threshold for classifying clinically meaningful improvement in children/adolescents receiving pharmacotherapy for TS in clinical practice.
To cite this abstract in AMA style:
J. Mcguire, G. Karkanias, R. Bittman, S. Atkinson, F. Munschauer, S. Wanaski, T. Cunniff, D. Gilbert. Determination of the Minimal Clinically Important Difference in the Yale Global Tic Severity Scale Total Tic Score in a Pediatric Population With Tourette Syndrome Receiving Pharmacotherapy [abstract]. Mov Disord. 2025; 40 (suppl 1). https://www.mdsabstracts.org/abstract/determination-of-the-minimal-clinically-important-difference-in-the-yale-global-tic-severity-scale-total-tic-score-in-a-pediatric-population-with-tourette-syndrome-receiving-pharmacotherapy/. Accessed October 5, 2025.« Back to 2025 International Congress
MDS Abstracts - https://www.mdsabstracts.org/abstract/determination-of-the-minimal-clinically-important-difference-in-the-yale-global-tic-severity-scale-total-tic-score-in-a-pediatric-population-with-tourette-syndrome-receiving-pharmacotherapy/