Development and Validation of a Patient-Reported Outcome Measure of Ataxia.

BACKGROUND Assessment of cerebellar ataxia has been confined to rating scales, gait laboratories, and wearable sensors agnostic to patient input. OBJECTIVES The objective of this study was to develop a Patient-Reported Outcome Measure of Ataxia. METHODS (1) The conceptual framework, item pool development, and domain selection were developed using online surveys completed by 147 ataxia patients. Responses generated the 70-item Patient-Reported Outcome Measure of Ataxia, scored on a 0-4 Likert scale. (2) Cognitive debrief in 17 patients grouped by ataxia severity assessed content validity, readability, and comprehension. (3) Psychometric validation by 78 anonymized ataxia patients included test-retest reliability, responsiveness to ataxia severity, internal consistency (Cronbach's alpha), and item-total score correlations. (4) Validation was tested against measures of ataxia and quality of life in 20 patients. (5) Items were rank-ordered to develop the Patient-Reported Outcome Measure of Ataxia Short Form. RESULTS Three thousand eight hundred fifty-five symptoms were grouped into 3 domains (physical, activities of daily living, mental health) and 14 subdomains. The Patient-Reported Outcome Measure of Ataxia was comprehensible, important, and relevant. Internal consistency, reliability, and test-retest reliability were high. Scores were responsive to ataxia severity stages 1, 2, and 3: mean ± standard deviation 81.0 ± 37.0, 129.6 ± 32.0, and 151.1 ± 41.3, respectively (r = 0.58, P < 0.0001). The Patient-Reported Outcome Measure of Ataxia was validated against measures of motor ataxia, quality of life, and mental health. It had an R2 of 0.82 (P < 0.0001) with the preliminary Patient-Reported Outcome Measure of Ataxia Short Form. CONCLUSIONS The Patient-Reported Outcome Measure of Ataxia is valid and reliable in cerebellar ataxia patients. It has the potential to improve patient care and natural history studies and quantify the efficacy of novel therapeutics in clinical trials. © 2021 International Parkinson and Movement Disorder Society.