Currently utilized clinician-rated symptom scales for tardive dyskinesia (TD) have not kept up with the expanding spectrum of TD phenomenology. The objective of this study was to develop and test the reliability of a new instrument, the CTI.

A movement disorder neurologist devised the outline of the scale. A steering committee (four neurologists and two psychiatrists) provided revisions until consensus was reached. The resulting instrument assesses frequency of abnormal movements of the eye/eyelid/face, tongue/mouth, jaw, limb/trunk, complex movements (e.g., handwringing, self-caressing), and vocalizations. The CTI rates symptoms from 0–3 with 0 = absent, 1 = infrequent/intermittent or only present with activating maneuvers, 2 = frequent intermittent, brief periods without movements, 3 = constant or nearly constant. Functional impairments including activities of daily living (ADL), social impairment, symptom bother, and harm are rated 0–3 with 0 = patient is unaware or unaffected, 1 = symptoms mildly impact patient, 2 = symptoms moderately impact patient, 3 = symptoms severely impact patient. Following institutional review board approval, the CTI underwent inter-rater and test-retest reliability testing. Videos of patient TD examinations were obtained and reviewed by two movement disorder specialists to confirm the diagnosis of TD by consensus and the adequacy to demonstrate a TD-consistent movement. Vignettes were created to include patients’ symptom descriptions and functional, social, or occupational impairments/limitations. Four clinicians rated each video/vignette. Selected videos/vignettes were also subject to an intra-rater retest. Interrater agreement was analyzed via 2-way random-effects interclass correlation (ICC) and test-retest agreement assessment utilizing Kendall’s tau-b.

45 video/vignettes were assessed for interrater reliability, and 16 for test-retest reliability. ICCs for movement frequency were as follows: abnormal eye movement .89; abnormal tongue/mouth movement .91; abnormal jaw movement .89; abnormal limb movement .76; complex movement .87; abnormal vocalization .77; and functional impairments including harm .82; social embarrassment .88; ADLs .83; and symptom bother .92. Retests were conducted on mean (SD) 15 (3) days later with scores ranging from .66–.87.

The CTI is a new instrument with good reliability in assessing TD symptoms and functional impacts. Future validation study is warranted.

Neurocrine Biosciences