Minimal Clinically Important Difference of the Scale for the Assessment and Rating of Ataxia

BACKGROUND: The Scale for the Assessment and Rating of Ataxia (SARA) is the most used outcome measure in clinical trials for cerebellar ataxias. The minimal clinically important difference (MCID), a parameter used to assess meaningful change, is not clearly defined. OBJECTIVE: To help define MCID for SARA. METHODS: Sixty-two individuals with cerebellar ataxias participated in a home-exercise clinical trial. Participants had outcomes assessed [SARA, Timed Up and Go (TUG), Dynamic Gait Index (DGI), gait speed, Patient Global Impression of Change (PGIC)] at 0-, 6-, 9-, and 12-months. Three methods were used to determine the MCID for SARA: anchor-based method, distribution-based method, and distribution-based mapping. RESULTS: The MCID for SARA using anchor-based method was 1.75. The distribution-based method and distribution-based mapping identified a median MCID score of 1.23. CONCLUSION: Synthesizing methods, we determined an MCID of 1.5 points. An accurate MCID is critical to ensure future treatments are clinically relevant.