Inter‐rater reliability of the International Cooperative Ataxia Rating Scale (ICARS)

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Abstract
We assessed the inter‐rater reliability of the 100‐point International Cooperative Ataxia Rating Scale (ICARS). Three neurologists independently rated videotaped ICARS examinations of 22 subjects with genetically determined ataxias (spinocerebellar ataxia [SCA] Type 1 in 11; SCA Type 2 in 1; Friedreich's ataxia in 10) and 4 controls. Scores on live ICARS assessment had ranged from 0 to 7 for controls and 11 to 74 for ataxic subjects (clinically very mildly affected to wheelchair‐bound). Inter‐rater correlation was very high for the total score (Kendall's ω 0.994, 95% confidence interval, 0.988–0.997), and high to very high for each component subscore (0.791 for speech to 0.994 for posture/gait). All correlations were significant at P < 0.00001. The ICARS exhibits very high inter‐rater reliability even without prior observer standardisation and is sensitive to a range of ataxia severities from very mild to severe. © 2003 Movement Disorder Society