Novel Scale Accurately Assesses Real-World TD Severity & Functional Impact

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The novel Clinician’s Tardive Inventory has been validated as a tool that reliably measures the real-world severity and impact of tardive dyskinesia.

“Current clinician-rated tardive dyskinesia (TD) symptom scales do not address expanding clinical signs and functional impacts,” researchers wrote in Parkinsonism and Related Disorders. “The Clinician’s Tardive Inventory (CTI) is a newly developed instrument documenting designed by movement disorder specialists and psychiatrists.”

The CTI includes six domains that describe the presence, frequency, amplitude, and functional impacts of 33 abnormal movements of the eye/eyelid/face, tongue/mouth, jaw, limb/trunk; complex movements, such as handwringing and self-caressing, indicating akathisia; and vocalizations, including volume. All of these can be observed during a patient encounter, the researchers noted.

The CTI was described in 2024 by Richard M. Trosch, MD, and colleagues. For the present validation study of the instrument, Dr. Trosch and the study team rated the CTI and the Abnormal Involuntary Movement Scale (AIMS) in the same patient. They determined construct validity based on agreement between the CTI combined severity score (CSS; CTI-CSS) and the AIMS dyskinesia score.

Scoring Systems Used in CTI

The frequency of symptoms is rated on a scale of zero to three:

• 0: Absent
• 1: Infrequent/intermittent or only present with activating maneuvers (<40% present during assessment)
• 2: Frequent intermittent: brief periods without movements (40% to 75% present during assessment)
• 3: Constant or nearly constant (>75% present during assessment)

Amplitude is also rated from zero to three, with zero being absent, one being low, two being moderate, and three being high. Movements with only one possible amplitude, such as bruxism (jaw clenching), were assigned default amplitudes.

Scored functional impairments include activities of daily living (ADL), leisure or occupation, social impairment, symptom distress, and physical harm. All are rated on a scale from zero to three, all based on the impact on the patient:

• 0: Patient is unaware or unaffected
• 1: Symptoms have a mild impact
• 2: Symptoms have a moderate impact
• 3: Symptoms have a severe impact

Correlations Between CTI, AIMS & Functional Scores

In total, Dr. Trosch and colleagues analyzed 70 videos with paired vignettes with both the CTI and AIMS. The mean age of patients was 59 years (range, 30–84 years) and 73.0% were women. The most frequent movements documented as present via the CTI were lip pursing, puckering, curling, or protrusion (71.0%), tongue darting (44.0%), jaw movements (36.0%), and leg swinging/bouncing (33.0%). The mean AIMS dyskinesia score was 9.3 (range, 2.0–25.0). The mean for the CTI-CSS was 8.1 (range, 1.0–26.0) and the CTI Functional Score was 1.8 (range, 0.0–3.0).

For the primary endpoint analysis, the CSS exhibited a strong correlation versus the AIMS dyskinesia score: 0.770 (95% CI, 0.654–0.851). The CSS was not well correlated with the CTI Functional Score, the AIMS question 9 (incapacitation due to abnormal movements), or the AIMS question 10 (patient awareness of abnormal movements).

However, the CTI Functional Score was sufficiently correlated with the AIMS functional question 9 (0.626; 95% CI, 0.458–0.750), and highly correlated with question 10 (0.771; 95% CI, 0.655–0.852) but not the AIMS dyskinesia score.

“Interestingly, in exploratory analysis, the AIMS dyskinesia score was also not well correlated with either AIMS functional questions 9 or 10,” Dr. Trosch and colleagues wrote.

Working Toward Use of CTI in Clinical Settings

 The CTI was developed to meet the need for a reliable, valid, easy-to-use TD screening tool that integrated real-world descriptions of TD movements in patients with exposure to a dopamine receptor-blocking agent, the authors continued.

“We believe this instrument can be utilized to document a TD exam, follow the course of TD motor signs, and serve as a rating scale to assess TD severity and functional impacts,” Dr. Trosch and colleagues wrote.

The researchers acknowledged that the study did not validate the instrument longitudinally but noted that the CTI has the potential to enable longitudinal patient follow-up, including as a tool to monitor patient responses to therapeutic interventions.

“The instrument shows face validity and construct validity in assessing the severity of TD signs,” Dr. Trosch and colleagues wrote. “Future studies are needed to determine validity in face-to-face clinical encounters, generalizability to routine clinical care, and to understand minimally clinically important differences in longitudinal patient follow-up in a clinical setting.”