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International cooperative ataxia rating scale (ICARS): Appropriate for studies of Friedreich's ataxia?

Authors

  • Stefan J. Cano PhD,

    1. Department of Clinical Neurosciences, Royal Free & University College Medical School, London, United Kingdom
    2. Neurological Outcome Measures Unit, Institute of Neurology, London, United Kingdom
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  • Jeremy C. Hobart PhD,

    Corresponding author
    1. Neurological Outcome Measures Unit, Institute of Neurology, London, United Kingdom
    2. Department of Clinical Neurosciences, Peninsula Medical School, Derriford Hospital, Plymouth, United Kingdom
    • Department of Clinical Neurosciences, Peninsula Medical School, Derriford Hospital, Plymouth PL6 8DH, United Kingdom
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  • Paul E. Hart MD,

    1. Department of Clinical Neurosciences, Royal Free & University College Medical School, London, United Kingdom
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  • L.V. Prasad Korlipara MD,

    1. Department of Clinical Neurosciences, Royal Free & University College Medical School, London, United Kingdom
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  • Anthony H.V. Schapira MD,

    1. Department of Clinical Neurosciences, Royal Free & University College Medical School, London, United Kingdom
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  • J. Mark Cooper PhD

    1. Department of Clinical Neurosciences, Royal Free & University College Medical School, London, United Kingdom
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Abstract

Clinicians require scientifically rigorous, clinically meaningful rating scales to evaluate the health impact of disease and treatment that cannot be measured using conventional laboratory instruments. This study evaluated the psychometric properties of the International Cooperative Ataxia Rating Scale (ICARS), a commonly used clinician-rated measure, in Friedreich's ataxia (FRDA). People with confirmed FRDA were assessed by using the ICARS. Two assumptions of its measurement model were tested: the legitimacy of reporting ICARS scores in FRDA, and the acceptability, reliability, and validity of total and subscale scores. Seventy-seven people with FRDA were assessed. The ICARS total score effectively satisfied all psychometric criteria tested. The posture and gait disturbances subscale also performed well. The other three subscales did not pass standard criteria for tests of scaling assumptions, reliability, and validity. This small study recommends only the use of the ICARS total score as a measure of FRDA. However, the extent to which this score quantifies the true extent of FRDA remains uncertain as our validity testing was limited, partly by the lack of appropriate validating measures. Further validity testing, and examination of responsiveness, is required before the ICARS can be recommended as an outcome measure for treatment trials of FDRA. © 2005 Movement Disorder Society

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