Longitudinal change in the items of the Tardive Dyskinesia Impact Scale (TDIS), a disease-specific, patient-reported outcome measure using data from KINECT®3 (NCT02274558) and KINECT®4 (NCT02405091)
Introduction: Tardive dyskinesia (TD) is a potentially disabling involuntary movement disorder due to dopamine receptor-blocking agent exposure and can impair physical, psychological, functional, and socio-emotional well-being. The 11-item Tardive Dyskinesia Impact Scale (TDIS) is a reliable, valid, TD-specific, patient reported outcome measure evaluating TD symptom impact over the previous 7 days. Two domain scores and an overall score are computed. Item response theory analyses confirmed that TDIS has high reliability and discrimination, and each question captures distinct aspects of TD impact. We describe changes in TDIS individual items over time.
Methods: Combined data from 252 subjects with a baseline and ≥1 follow-up assessment, pooled across treatment assignments (Nf71 placebo; Nf181 active treatment), who completed Phase 3 TD trials KINECT®3 or KINECT®4 were analyzed. Mean TDIS scores (range 0-4) for each item were evaluated at baseline through Week 48. Higher scores indicate worse functioning; negative change scores indicate improvement.
Results: Results showed consistent downward trend across all items, suggesting treatment improved TDIS scores for both physical and socio-emotional domains. The most impacted items at baseline were self-consciousness (mean score: 1.99), embarrassment (1.89), mouth noises (1.80), unwanted attention (1.74), and writing (1.29). Improvements (≥1 point decline from baseline to week 48) were observed in self-consciousness (mean change –1.23), embarrassment (–1.20), and mouth noises (−1.05). Unwanted attention (−0.99) and writing (−0.75) also considerably improved.
Conclusions: All TDIS items showed improvement over 48 weeks, particularly social and emotional impacts. These results support the use of TDIS to show longitudinal change in TD burden.
