Tourette syndrome and persistent tic disorders (collectively, TS) are impairing childhood-onset neuropsychiatric conditions. Utilizing evidence-based assessments (EBA) is standard for effective and accurate screening, diagnosis, and monitoring of TS. EBAs consist of brief screening instruments, structured/semi-structured clinician-administered interviews, self-report, and parent-report and child-report. This article provides an overview of the quality, utility, and psychometric properties of available assessments to determine the presence of TS, evaluate symptom severity, and capture associated phenomenology (eg, premonitory urges, quality of life). The article concludes with considerations for best clinical practices and future directions for the EBA of TS.
Key points
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Tourette syndrome and other persistent tic disorders (collectively referred to as TS) share similar features with other neuropsychiatric conditions (eg, obsessive–compulsive disorder). The use of evidence-based assessments (EBA), particularly diagnostic interviews, can assist clinicians with the accurate diagnosis and evaluation of TS symptomatology.
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Psychometrically validated instruments allow clinicians and researchers to evaluate, target, and monitor clinical improvement of tic symptoms and associated features of TS (eg, premonitory urges, functional impairment, quality of life, family accommodation, functional consequences of tics) over the course of intervention.
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When conducting EBA of TS, assessors should strive to balance utilizing the most relevant and psychometrically valid instruments with what is feasible given the goals/constraints of the patient assessment.
Introduction
Tourette syndrome and other persistent tic disorders (collectively referred to as TS) are impairing childhood-onset neuropsychiatric conditions that affect up to 0.77% individuals. The hallmark symptoms of TS are tics—involuntary motor movements and vocalizations. While tics are the most overt symptom of TS, individuals with TS may also experience aversive somatosensory sensations that precede tics called premonitory urges. , Beyond tics and premonitory urges, individuals with TS commonly experience challenging, co-occurring affective states (eg, anxiety, irritability, anger) and psychiatric comorbidity (eg, anxiety disorders, attention-deficit hyperactivity disorder [ADHD], obsessive–compulsive disorder [OCD]). , , Collectively, tics, premonitory urges, psychiatric comorbidities, and co-occurring difficulties with emotion regulation can contribute to significant impairment and reduced quality of life (QoL) for many individuals with TS across the lifespan.
Evidence-based assessment (EBA) is instrumental in the identification of TS and the evaluation of its clinical presentation. First, EBA plays an important role in screening for TS symptomatology and allowing for an accurate differential diagnosis of TS from other neuropsychiatric conditions that may share similar features. Second, EBA for TS allows clinicians to gauge tic severity in a standardized fashion. This allows clinicians to select the most appropriate form of evidence-based treatment of individuals with TS based on clinical practice guidelines. Third, psychometrically sound instruments that are reliable, valid, and treatment-sensitive allow clinicians to monitor changes in symptom severity and measure improvement over treatment and clinical research. By precisely capturing symptom severity and associated clinical features, treatment providers and researchers alike can gain insight into optimal treatment targets for TS. This review aims to provide a summary of TS measures with psychometric properties to guide clinicians in the application of EBA to tics and associated phenomena.
Screening for Tourette syndrome
When time is limited, assessors can take advantage of brief, cost-effective screening assessments to gauge the presence of tics. While screening measures should not be used to definitively diagnose TS, these instruments can be used to inform next steps in the clinical evaluation process. The Motor or Vocal Inventory of Tics (MOVeIT-14) is a brief screener in which parents or youth rate the presence and frequency of a variety of motor and vocal tics on a 3 point scale. Evidence suggests that both parent-report and child-report versions of the MOVeIT-14 demonstrate strong internal validity, excellent convergent validity with the Yale Global Tic Severity Scale (YGTSS), good parent–child agreement, and reasonable diagnostic sensitivity and specificity. , , The Description of Tic Symptoms (DoTS) is another brief parent-report and child-report questionnaire that captures information on the presence of tics, their onset, and other clinical features of TS. , Although it is still undergoing psychometric evaluation, preliminary evidence suggests that parent-report and child-report versions of the DoTS exhibit strong diagnostic sensitivity and specificity. , At this time, the MOVeIT-14 has the best evidence as a screener for tic symptoms. However, more research is needed to validate the properties of these instruments; furthermore, it is imperative to recognize that these tools are meant to serve as screeners for tic symptoms and should not replace a diagnostic interview.
Making a Tourette syndrome diagnosis
According to the Diagnostic and Statistical Manual of Mental Illness, fifth edition (DSM-5), TS diagnoses are conferred on the basis of several criteria, including age of onset; type of tic(s) present; and absence of any rule-out conditions. The diagnoses of provisional tic disorder, chronic motor/chronic vocal tic disorder, and Tourette syndrome all require the onset of tic symptoms before the age of 18 years, along with the absence of other possible contributing medical conditions or substance use. To meet criteria for a diagnosis of provisional tic disorder, individuals must exhibit either a single tic, or multiple tics, for a period of less than 1 year. The diagnosis of chronic motor or chronic vocal tic disorder is warranted when only motor tics or only vocal tics have been present for more than 1 year, respectively. A Tourette syndrome diagnosis is appropriate when multiple motor and one or more vocal tics have been present for a period of longer than 1 year. TS can oftentimes present alongside co-occurring conditions, making diagnosis challenging. Indeed, approximately 86% of patients with TS have one or more comorbid psychiatric conditions.
Several validated diagnostic interviews exist for TS and co-occurring conditions, such as the Mini International Neuropsychiatric Interview for Children and Adolescents, the Diagnostic Interview Schedule for Children, the Diagnostic Interview for Anxiety, Mood, and Obsessive–Compulsive and Related Neuropsychiatric Disorders (DIAMOND), and the DIAMOND in Children and Adolescents (DIAMOND-KID). While comprehensive structured and semi-structured diagnostic assessments offer the improved ability to differentiate TS from other diagnoses, clinicians should be mindful of the limitations of these instruments. Comprehensive semi-structured and structured interviews are time intensive and should only be administered to improve diagnostic clarity and inform the selection of evidence-based interventions.
Clinician-Rated Measures of Tic Symptom Severity
Yale Global Tic Severity Scale/Yale Global Tic Severity Scale-Revised
While many instruments have been used to capture tic severity (see Ref for a comprehensive review), the YGTSS is recognized as the gold-standard outcome measure in clinical trials of TS. The YGTSS is a clinician-rated, semi-structured interview that captures the presence and severity of motor and vocal tics over the course of the past week. The YGTSS is made up of two elements. The first component is a Symptom Checklist, in which clinicians endorse the presence of motor and vocal tics separately. Then, clinicians use information from the Symptom Checklist to guide ratings on the severity scale, in which raters score the number, frequency, intensity, complexity, and interference of motor and vocal tics separately over the past week. Ratings are tabulated to produce Motor (range 0–25) and Vocal (range 0–25) Tic Scores, which are then summed to yield a Total Tic Score (range 0–50). The YGTSS also includes a single item that captures tic-related impairment, generating an impairment score (range 0–50). Both scores are summed to provide the global severity score (range 0–100). Since its initial development, the YGTSS has been found to have strong psychometric properties, including good internal consistency, test–retest reliability, and appropriate convergent and divergent validity ( Table 1 ). , , The YGTSS has demonstrated treatment sensitivity in clinical trials among adults and youth with TS.
| Measure | Brief Description | Reliability | Validity | Treatment Sensitivity |
|---|---|---|---|---|
| Yale Global Tic Severity Scale (YGTSS)/Yale Global Tic Severity Scale-Revised (YGTSS-R) | A semi-structured interview assesses motor and vocal tic symptoms in past week comprised of a Symptom Checklist, and Severity subscales. Motor and Vocal Severity subscales are summed to create a Total Tic Severity score. A Global Tic Severity score is generated by adding the Tic Impairment score to the Total Tic Severity score. , | Internal consistency: α = 0.92–0.94 ; Ω = 0.56–0.58 ; Global Tic Severity : α = .67, Tic Subscales : α = .80–.87 Inter-rater reliability: Intraclass correlation coefficient (ICC) = 0.62–0.91 Test–retest reliability: ICC = .77–.90 | Convergent validity : Scores correlate with other clinician-reports ( r = 0.46–.91) and parent-reports of tics ( r = .58–.67) ; Total Tic Score correlates with measures of impairment ( r = 0.5–0.65) Discriminant validity : Nonsignificant correlations with measures of ADHD, moderate correlations with measures of OCD ( r = .30–.39) ; small correlations with measures of OCD ( r = 0.21–0.27) and ADHD (r = 0.20–0.25) ; nonsignificant correlations to clinician-rated OCD severity ( r = .01–.15), parent-reported externalizing and internalizing behavior ( r = −.07–.20), child-report of depression ( r = .02–.26) and anxiety ( r = −.06–.28) | Yes , , |
| Hopkins Motor / Vocal Tic Scale (HM/VTS) | Top five nominated motor and top five vocal tics are rated by a clinician on a five point bothersomeness scale. | Inter-rater reliability: ρ = 0.88–0.93 | Convergent validity: Large correlations with other measures of tic severity ( ρ = .71–.87) Discriminant validity: Nonsignificant correlations to ADHD, OCD symptoms | Not available |
In recent years, the YGTSS has been updated to enhance its precision (Yale Global Tic Severity Scale-Revised [YGTSS-R]). Changes in the YGTSS-R include minor revisions to anchor point descriptions for three severity dimensions (ie, frequency, complexity, and interference) to promote full use of scales for these dimensions, as well as an expanded Vocal Tic Symptom Checklist. The revisions to the YGTSS do not contraindicate the reliability, validity, and/or treatment sensitivity of the original scale. It is important to note that these revisions do not negate prior work using the measure but rather enhance the precision of its use moving forward.
Hopkins Motor/Vocal Tic Scale
The Hopkins Motor/Vocal Tic Scale (HM/VTS) is designed to measure the most bothersome tic symptoms. The original scale was developed such that participants nominated up to five motor and vocal tics each (10 total tics max), which were then rated by a clinician on a visual analogue 10 cm scale to indicate “absent tics” to “severe tics.” The HM/VTS has since been modified for use in clinical trials. , In the adapted version, nominated tics are rated by a clinician on a five point scale as follows: 0 (none), 1 (mild), 2 (moderate), 3 (moderately severe), and 4 (severe). Clinicians consider the frequency, forcefulness, interference, and subjective distress of tics when making individual bothersomeness ratings. Motor and vocal tic ratings are summed to produce separate subscale scores, which are then added together to yield a Total Tic Score. The HM/VTS has strong inter-rater reliability values for both motor and vocal tic scores, good convergent validity with other measures of tic severity (ie, YGTSS), and good discriminant validity (ie, nonsignificant correlations with measures of ADHD, OCD; see Table 1 ).
Self-report measures of tic severity
Clinician-rated instruments are valuable to obtain a trained perspective on TS symptom severity but can be resource intensive. Self-report scales are an efficient strategy to gain insight into tic symptoms from patients’ perspectives. Self-report scales tend to be relatively easy to administer and score, and can add to the clinical picture when combined with other EBA for a comprehensive evaluation. Among available surveys, the Adult Tic Questionnaire (ATQ) and the Motor tic, Obsessions and compulsions, Vocal tic Evaluation Survey (MOVES) are widely used.
The Adult Tic Questionnaire
The ATQ is a brief self-report survey for adolescents and adults that captures tic severity over the past week. The assessment includes a list of 14 common motor tics and 13 common vocal tics. The reporter is instructed to indicate the presence of certain tics in the past week and then rate the frequency and intensity of each tic on a 4 point Likert scale. The ATQ yields Motor Tic Severity, Vocal Tic Severity, and Total Tic Severity scores. Additionally, subscale scores can be tabulated for the frequency and intensity of motor, vocal, and all tics. The ATQ was originally piloted during the original behavior therapy clinical trials for adults with TS. Psychometric analyses suggest that the Motor Tic Severity, Vocal Tic Severity, and Total Tic Severity scales all demonstrate strong internal consistency, with good test–retest reliability ( Table 2 ). ATQ scores demonstrate appropriate convergent and divergent validity, having large, positive correlations with other relevant metrics of clinician-rated tic severity (ie, YGTSS), and small correlations with non-TS assessments (ie, Yale-Brown Obsessive Compulsive Scale [Y-BOCS], ADHD Rating Scale [ADHD-RS]). The ATQ has not yet been evaluated for treatment sensitivity.
| Measure | Brief Description | Reliability | Validity | Treatment Sensitivity |
|---|---|---|---|---|
| Adult Tic Questionnaire (ATQ) | Self-report for adolescents and adults with TS captures frequency and intensity of 14 common motor tics and 13 vocal tics. | Internal consistency — Overall Severity Scores : α = 0.86–0.91; Total Tic Frequency Scores : α = 0.75–0.83; Total Intensity Scores : 0.73–0.83 Test–retest reliability: r = 0.81–0.88 | Convergent validity : Total score correlates with measures of impairment ( r = 0.52–0.73) when compared to YGTSS Discriminant validity : Small-to-moderate correlations with Y-BOCS and ADHD-RS ( r = 0.21–0.34) | Not available |
| Motor Tic, Obsession and Compulsion, and Vocal tic Evaluation Survey (MOVES) | 20 item adolescent and adult self-report survey measures frequency of symptoms over the past four weeks. Generates scores on five subscales: Motor Tics; Vocal Tics; Obsessions; Compulsions; and Associated Symptoms (echolalia, echopraxia, coprolalia, copropraxia). | Internal consistency: Split-half reliability coefficient = 0.87 Test–retest reliability: r = 0.54–0.72 | Convergent validity : MOVES Tic score correlates with measures of YGTSS ( r = 0.73), MOVES OCD Score correlates with Assessor’s Scale for OCD (r = 0.60) | Yes |
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