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

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.

The Heart in Friedreich Ataxia

“…The ICARS consists of 19 items addressing oculomotor function, speech, kinetic functions, posture, and gait. 14,15 Patients who were able to walk at least 10 m with or without walking aids but without the help of an accompanying person were classified as ambulatory. For assessment of the ICARS score, in every center a rater and a backup rater were trained and certified by the study's clinical research physician, using study-specific training materials (including video training).…”

The scale for the assessment and rating of ataxia correlates with dysarthria assessment in Friedreich's ataxia

“…SARA underwent a validation for SCAs and FRDA as well, and showed to measure ataxia linearly over a wide range of disease severity. Besides, SARA yielded a high correlation with the Friedreich's ataxia Rating Scale (FARS) and International Cooperative Ataxia Rating Scale (ICARS) [9,10]. The milestones of disease assessment is a widely used four-point scale for evaluating a person's mobility status ranging from normal to bed-ridden and death [11].…”

Evaluating the progression of Friedreich ataxia and its treatment

“…Later, in a study in which three neurologists independently assessed videotaped examinations of patients with FRDA or autosomal dominant spinocerebellar ataxia, the ICARS was shown to have high inter-rater reliability [14]. In addition, the psychometric properties of the ICARS for use in FRDA were assessed in a study of 77 individuals [15]. The following aspects of the ICARS were tested: (a) item-total correlation, (b) item-own scale correlation, (c) floor and ceiling effects, (d) skewness, (e) internal consistency, (f) test-retest reproducibility, (g) inter-correlations between total score and sub-scale scores, and (h) correlations between total and sub-scale scores and age and disease duration.…”