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. 2019 Oct 29;5(6):371.
doi: 10.1212/NXG.0000000000000371. eCollection 2019 Dec.

Psychometric properties of the Friedreich Ataxia Rating Scale

Christian Rummey  1 , Louise A Corben  1 , Martin B Delatycki  1 , S H Subramony  1 , Khalaf Bushara  1 , Christopher M Gomez  1 , Joseph Chad Hoyle  1 , Grace Yoon  1 , Bernard Ravina  1 , Katherine D Mathews  1 , George Wilmot  1 , Theresa Zesiewicz  1 , Susan Perlman  1 , Jennifer M Farmer  1 , David R Lynch  1
Affiliations

Psychometric properties of the Friedreich Ataxia Rating Scale

Christian Rummey et al. Neurol Genet. .

Abstract

Objective: To investigate the psychometric properties of the Friedreich Ataxia Rating Scale neurologic examination (FARSn) and its subscores, as well as the influence of the modifications resulting in the now widely used modified FARS (mFARS) examination.

Methods: Based on cross-sectional FARS data from the FA-Clinical Outcome Measures cohort, we conducted correlation-based psychometric analyses to investigate the interplay of items and subscores within the FARSn/mFARS constructs.

Results: The results provide support for both the FARSn and the mFARS constructs, as well as individually for their upper limb and lower limb coordination components. The omission of the peripheral nervous system subscore (D) and 2 items of the bulbar subscore (A) in the mFARS strengthens the overall construct compared with the complete FARS.

Conclusions: A correlation-based psychometric analysis of the neurologic FARSn score justifies the overall validity of the scale. In addition, omission of items of limited functional significance as created in the mFARS improves the features of the measures. Such information is crucial to the ongoing application of the mFARS in natural history studies and clinical trials. Additional analyses of longitudinal changes will be necessary to fully ascertain its utility, especially in nonambulant patients.

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Figures

Figure 1
Figure 1. Measurement model of the neurologic examination of the FARSn and the modified FARS (mFARS)
Maximum score/subscale/item scores are shown in brackets. Items in subscales B, C, and D are conducted separately on lateral sides; ** items A1 and A2 are excluded in the mFARS examination. FARS = Friedreich Ataxia Rating Scale; mFARS = modified FARS.
Figure 2
Figure 2. Heat map of individual items within the modified FARS
Data are grouped by subscales. Five blue hues (from light to dark) correspond to increasing item scores in steps of 20%. FARS = Friedreich Ataxia Rating Scale.
See this image and copyright information in PMC

Comment in

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