Yale Global Tic Severity Scale (YGTSS): Psychometric Quality of the Gold Standard for Tic Assessment Based on the Large-Scale EMTICS Study

Abstract

The Yale Global Tic Severity Scale (YGTSS) is a clinician-rated instrument considered as the gold standard for assessing tics in patients with Tourette's Syndrome and other tic disorders. Previous psychometric investigations of the YGTSS exhibit different limitations such as small sample sizes and insufficient methods. To overcome these shortcomings, we used a subsample of the large-scale “European Multicentre Tics in Children Study” (EMTICS) including 706 children and adolescents with a chronic tic disorder and investigated convergent, discriminant and factorial validity, as well as internal consistency of the YGTSS. Our results confirm acceptable convergent and good to very good discriminant validity, respectively, indicated by a sufficiently high correlation of the YGTSS total tic score with the Clinical Global Impression Scale for tics (rs = 0.65) and only low to medium correlations with clinical severity ratings of attention deficit/hyperactivity symptoms (rs = 0.24), obsessive–compulsive symptoms (rs = 27) as well as internalizing symptoms (rs = 0.27). Internal consistency was found to be acceptable (Ω = 0.58 for YGTSS total tic score). A confirmatory factor analysis supports the concept of the two factors “motor tics” and “phonic tics,” but still demonstrated just a marginal model fit (root mean square error of approximation = 0.09 [0.08; 0.10], comparative fit index = 0.90, and Tucker Lewis index = 0.87). A subsequent analysis of local misspecifications revealed correlated measurement errors, suggesting opportunities for improvement regarding the item wording. In conclusion, our results indicate acceptable psychometric quality of the YGTSS. However, taking the wide use and importance of the YGTSS into account, our results suggest the need for further investigations and improvements of the YGTSS. In addition, our results show limitations of the global severity score as a sum score indicating that the separate use of the total tic score and the impairment rating is more beneficial.

Endocannabinoid Modulation Using Monoacylglycerol Lipase Inhibition in Tourette Syndrome: A Phase 1 Randomized, Placebo-Controlled Study

“…On the other hand, both the YGTSS-TTS and the ATQ had to be adapted to the single-dose study design and used several times within a short period instead of tic assessment based on information from the previous week as instructed in the original versions. Furthermore, although the YGTSS has only recently been revised 31 further limitations of the YGTSS have been identified 32 . The ATQ shows a strong correlation with the YGTSS 32 ; however, it has not yet been widely used and further validation is missing 26 .…”

“…Furthermore, although the YGTSS has only recently been revised 31 further limitations of the YGTSS have been identified 32 . The ATQ shows a strong correlation with the YGTSS 32 ; however, it has not yet been widely used and further validation is missing 26 .…”

Correlation Between Tic Disorders and Serum 25-Hydroxyvitamin D Levels in Chinese Children

“…Five sum scores are then created: the total motor tic score (range 0–25), the total phonic tic score (range 0–25), the total tic score (TTS; sum of the total motor tic score and total phonic tic score), the overall impairment rating (one item; range 0–50), and the global severity score (sum of the TTS plus the overall impairment rating; range 0–100). TD cases with a total YGTSS score of less than 25 are considered mild; 25–50 as moderate; and greater than 50 as severe ( 15 ).…”

How brain networks tic: predicting tic severity through rs-fMRI dynamics in Tourette syndrome

“…In clinical practice, the YGTSS is used to track changes in tic behaviour or to monitor treatment outcomes (12) . A recent study has shown YGTSS to be robust against the effects of comorbidities such as OCD and ADHD, making it a good choice to investigate the pathophysiology of tics independently of other comorbidities (13) .…”