Minimally clinically important decline in the parkinsonian variant of multiple system atrophy

INTRODUCTION: We provide the first characterization of the minimally clinically important difference on the Unified Multiple System Atrophy Rating Scale in patients with the parkinsonian variant of early MSA. METHODS: Data from a randomized controlled trial of rasagiline were analyzed using clinical global impression as an anchor. Because too few patients improved with treatment, analyses were limited to defining scale cutoffs that discriminated between minimal worsening and no change. RESULTS: Based on receiver operating characteristic curves, minimally clinically important differences were 1.5 points on the activities of daily living scale, 1.5 points on the motor scale, and 3.5 points on the total scale. CONCLUSIONS: Appreciation of the minimally clinically important difference is important when deciding if statistically significant effects should influence practice. For the Unified Multiple System Atrophy Rating Scale, further work is required to establish cutoffs for improvement, extend relevance to cerebellar-predominant disease, and characterize progression rates at different disease stages.