Minimal Clinically Important Difference in Abnormal Involuntary Movement Scale Score Based on Clinical and Patient Global Impression of Change in Patients With Tardive Dyskinesia Treated With Deutetrabenazine

Background: Deutetrabenazine is FDA approved for tardive dyskinesia (TD) based on two 12-week, placebo-controlled studies evaluating safety and efficacy in patients with baseline Abnormal Involuntary Movement Scale (AIMS) score ‚â•6. This analysis assessed Minimal Clinically Important Difference (MCID) in AIMS score in patients with TD treated with deutetrabenazine.

Methods: MCID analyses were performed based on Patient Global Impression of Change (PGIC) and Clinical Global Impression of Change (CGIC) as anchors described by Hauser et al., where MCID is the difference between patients treated with deutetrabenazine who were minimally improved and patients treated with placebo who were unchanged. Additional MCID definitions were explored: difference between patients who demonstrated treatment improvement versus those who did not (Method 2); difference between patients who demonstrated treatment success versus those who did not (Method 3).

Results: 295 patients were analyzed. Based on PGIC, the suggested MCID was –2.8. Results were similar for Method 2 (75% of patients had treatment improvement; MCID=–2.8) and Method 3 (38% of patients had treatment success; MCID=–2.6). Based on CGIC, the suggested MCID was –2.6. Results were similar for Method 2 (76% of patients had treatment improvement; MCID=–2.8) and Method 3 (41% of patients had treatment success; MCID=–3.0). Therefore, the suggested MCID for deutetrabenazine is –3. 

Conclusions: The MCID for change in AIMS score based on PGIC and CGIC for deutetrabenazine was –3 regardless of the analytical method. Findings suggest an AIMS score reduction of ~3 is associated with clinically meaningful improvement in TD symptoms.