Clinical relevance of treatment with onabotulinumtoxina in patients with cervical dystonia: Results from the cd probe study

Objective: To explore minimal clinically important change perceived by patients as beneficial by the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) using data from the Cervical Dystonia Patient Registry for Observation of OnabotulinumtoxinA Efficacy (CD PROBE) study. Background: Although ≥10-point or ≥30% difference has been reported for defining clinically important change, there is no validated definition of clinically meaningful response to onabotulinumtoxinA treatment for CD. Design/Methods: CD PROBE is a multicenter, prospective clinical registry that recruited CD patients from 88 US sites. CD patients who were new to botulinum toxin therapy or had not received it for >16 weeks and were deemed suitable for onabotulinumtoxinA received 3 cycles of drug. Changes from baseline in TWSTRS scores were correlated with clinical improvement as assessed by the Patient or Clinical Global Impression of Change (PGIC/CGIC) scales. The model was discriminated using logistic regression; good discrimination was defined as >70% correct classification of PGIC or CGIC based on TWSTRS scores. We report on the 479 patients who completed the study. Results: Mean TWSTRS score significantly decreased from baseline to final visit (39.2 to 27.1, P