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. 2024 Oct;23(5):2095-2108.
doi: 10.1007/s12311-024-01707-9. Epub 2024 Jun 12.

Psychometric Validation of the Modified Functional Scale for the Assessment and Rating of Ataxia (f-SARA) in Patients With Spinocerebellar Ataxia

Michele Potashman  1 , Evan Popoff  2 , Lauren Powell  2 , Ainsley Mackenzie  3 , Melissa Wolfe Beiner  3 , Vlad Coric  3 , Jeremy Schmahmann  4 , Gilbert L'Italien  3
Affiliations

Psychometric Validation of the Modified Functional Scale for the Assessment and Rating of Ataxia (f-SARA) in Patients With Spinocerebellar Ataxia

Michele Potashman et al. Cerebellum. 2024 Oct.

Abstract

This study aimed to generate evidence to support psychometric validity of the modified functional Scale for the Assessment and Rating of Ataxia (f-SARA) among patients with spinocerebellar ataxia (SCA). Psychometric measurement properties and minimal change thresholds of the f-SARA were evaluated using data from a cohort of SCA subjects (recruited at Massachusetts General Hospital [MGH]; n = 33) and data from a phase 3 trial of troriluzole in adults with SCA (NCT03701399 [Study 206]; n = 217), including a subset of patients with the SCA3 genotype (n = 89). f-SARA item ceiling effects were absent within the MGH cohort, while floor effects were present. Excellent internal consistency reliability was demonstrated (αtotal = 0.90; αitems-removed = 0.86-0.90), and item-to-total correlations were strong (r = 0.82-0.91, per item). High test-retest reliability was demonstrated with intraclass correlation coefficients of 0.91 (total) and 0.73-0.92 (items). Convergent and divergent validity was supported, with strong correlations observed between the f-SARA and similarly constructed scales (FARS-FUNC, BARS, PROM-ADL, and FARS-ADL; all p < 0.001) and weaker correlations observed among measures of differing constructs. Mean item and total scores increased with disease severity (by FARS-FUNC quartile; p < 0.001). A 1-point threshold for meaningful changes was supported as 0.5 × SD = 0.89, SEM = 1.12, and mean changes from baseline for patients classified as "improved," "no change," or "deteriorated" were -0.68, 0.02, and 0.58, respectively. Similar trends were observed in Study 206 all-SCA and SCA3 cohorts. The measurement properties of the f-SARA provide evidence of its psychometric validity, responsiveness, and suitability as a clinical outcome measure in patients with SCA, including those with SCA3.

Keywords: Outcomes assessment; Psychometrics; Spinocerebellar ataxias; Validation study.

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Conflict of interest statement

Michele Potashman, Ainsley Mackenzie, Melissa Wolfe Beiner, Vlad Coric, and Gilbert L’Italien are employees of Biohaven Pharmaceuticals, Inc; Evan Popoff and Lauren Powell are employees of Broadstreet HEOR, which received funds from Biohaven Pharmaceuticals, Inc, for this work; Jeremy Schmahmann declares no conflict of interests. He consults for Biohaven Pharmaceuticals and is site PI for Biohaven Pharmaceuticals clinical trials NCT03701399, NCT02960893, and NCT03952806; receives royalties from Oxford University Press, Elsevier, MacKeith Press, and Springer; and is the inventor of the Brief Ataxia Rating Scale, Cerebellar Cognitive Affective/Schmahmann Syndrome Scale, the Patient Reported Outcome Measure of Ataxia, and the Cerebellar Neuropsychiatry Rating Scale, which are licensed to the General Hospital Corporation.

Figures

Fig. 1
Fig. 1
All-SCA f-SARA eCDF by CGI-I (Study 206). CFB, change from baseline; CGI-I, Clinical Global Impression-Global Improvement Scale; eCDF, empirical cumulative distribution function; f-SARA, modified functional Scale for the Assessment and Rating of Ataxia; SCA, spinocerebellar ataxia
Fig. 2
Fig. 2
All-SCA f-SARA PDF by CGI-I (Study 206). CFB, change from baseline; CGI-I, Clinical Global Impression-Global Improvement Scale; f-SARA, modified functional Scale for the Assessment and Rating of Ataxia; PDF, probability density function; SCA, spinocerebellar ataxia
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