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International Cooperative Ataxia Rating Scale (ICARS)
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Supplemental: Friedreich's ataxia (FA) and Mitochondrial Disease (Mito)
Short Description of Instrument
The International Cooperative Ataxia Rating Scale (ICARS) is a commonly used evaluation and is composed of four clinical sub-scores involving the following: posture and gait, limb coordination, speech and oculomotor function. It was initially designed for longitudinal assessment of pharmacological therapies in patients with cerebellar ataxia.
Scoring and Psychometric Properties
Scoring: The ICARS score is the total sum of the sub scores and ranges from 0 to 100, with a score of 100 indicative of the most severely affected outcome.
Psychometric Properties: See Metz et al., 2013; Schmitz-Huebsch et al., 2006 and Storey et al., for psychometric property data.
Friedreich's ataxia-Specific:
Interrater Reliability: Excellent Interrater reliability (Kendall's w = 0.994 / 95% Confidence Interval (CI) = 0.988 - 0.997) for full scale (n = 22) (Storey et al., 2004)
Internal Consistency: Poor Cronbach's alpha = 0.69 (Burk et al., 2009)
Criterion Validity (Predictive/Concurrent): Adequate predictive validity for disease progression of 2.5 points +/- 0.18 points for early onset patients (< 14 years of age for first 20 years of disease) and later onset (> 14 years of age) 1.8 points +/- 0.27 points (Metz et al., 2012)
Strengths: ICARS scores strongly correlate with the Ataxia Functional Composite Scale (AFCS) and with the Scale for the Assessment and Rating of Ataxia (SARA). ICARS is widely used and achieves a good inter-rater reliability. In addition to cerebellar ataxias, it has also successfully been applied in Friedreich's ataxia, the prototype of an afferent ataxia.
Weaknesses: ICARS scores improve during normal development, until at least 13 years of age; thus, when used in pediatric studies, ICARS values could lead to misinterpretation of longitudinal outcomes, with "improved" scores being mistakenly representative of a therapeutic effect. ICARS scores may be difficult in < 4 years of age (dependent on child) and/or cognitive dysfunction. ICARS takes much more time to be administered than the SARA.
Rationale: This scale was developed by an ad hoc Committee of the World Federation of Neurology who proposed a 100-point semi-quantitative International Cooperative Ataxia Rating Scale with compartmentalized quantification of postural or stance disorders, limb ataxia, dysarthria and oculomotor disorders, in order that a subscore relating to each of these symptoms could be separately studied. The weight of each symptomatologic compartment was carefully designed with precise definition of the tests, to minimize interobserver variations. The overall goal was to develop a cooperative ataxia rating scale that could be used in multicenter double-blind studies. A semi-quantitative 100-point scale was chosen. The entire assessment is meant to last less than 30 minutes.
Key Reference:
Trouillas P, Takayanagi T, Hallett M, Currier RD, Subramony SH, Wessel K, Bryer A, Diener HC, Massaquoi S, Gomez CM, Coutinho P, Ben Hamida M, Campanella G, Filla A, Schut L, Timann D, Honnorat J, Nighoghossian N, Manyam B. International Cooperative Ataxia Rating Scale for pharmacological assessment of the cerebellar syndrome. The Ataxia Neuropharmacology Committee of the World Federation of Neurology. J Neurol Sci. 1997 Feb 12;145(2):205-11.
Additional References:
Burk K, Malzig U, Wolf S, Heck S, Dimitriadis K, Schmitz-Hubsch T, Hering S, Lindig TM, Haug V, Timmann D, Degen I, Kruse B, Dorr JM, Ratzka S, Ivo A, Schols L, Boesch S, Klockgether T, Klopstock T, Schulz JB. Comparison of three clinical rating scales in Friedreich ataxia (FRDA). Mov Disord. 2009 Sep 15;24(12):1779-84.
Cano SJ, Hobart JC, Hart PE, Korlipara LV, Schapira AH, Cooper JM. International Cooperative Ataxia Rating Scale (ICARS): appropriate for studies of Friedreich's ataxia? Mov Disord. 2005 Dec;20(12):1585-91.
Metz G, Coppard N, Cooper JM, Delatycki MB, Durr A, Di Prospero NA, Giunti P, Lynch DR, Schulz JB, Rummey C, Meier T. Rating disease progression of Friedreich's ataxia by the International Cooperative Ataxia Rating Scale: analysis of a 603-patient database. Brain. 2013 Jan;136(Pt 1):259-68.
Schmitz-Huebsch T, Tezenas du Montcel S, Baliko L, Boesch S, Bonato S, Fancellu R, Giunti P, Globas C, Kang JS, Kremer B, Mariotti C, Melegh B, Rakowicz M, Rola R, Romano S, Schoels L, Szymanski S, van de Warrenburg BP, Zdzienicka E, Duerr A, Klockgether T. Reliability and validity of the International Cooperative Ataxia Rating Scale: a study in 156 spinocerebellar ataxia patients. Mov Disord. 2006 May;21(5):699-704.
Sival DA, Brunt ER. The International Cooperative Ataxia Rating Scale shows strong age-dependency in children. Dev Med Child Neurol. 2009 Jul;51(7):571-2.
Storey E, Tuck K, Hester R, Hughes A, Churchyard A. Inter-rater reliability of the International Cooperative Ataxia Rating Scale (ICARS). Mov Disord. 2004 Feb;19(2):190-2.
Document last updated March 2024