Content Validity of the Friedreich Ataxia Rating Scale in Patients with Spinocerebellar Ataxia

The Friedreich Ataxia Rating Scale–Activities of Daily Living (FARS-ADL) is a validated and highly utilized measure for evaluating patients with Friedreich Ataxia. While construct validity of FARS-ADL has been shown for spinocerebellar ataxia (SCA), content validity has not been established. Individuals with SCA1 or SCA3 (n = 7) and healthcare professionals (HCPs) with SCA expertise (n = 8) participated in qualitative interviews evaluating the relevance, clarity, and clinical meaningfulness of FARS-ADL for assessment of individuals with SCA. Interviews were recorded, transcribed, coded, and analyzed by ATLAS.Ti v22 software. FARS-ADL concepts most frequently reported by individuals with SCA were difficulty walking (n = 7/7), falls (n = 6/7), speech difficulties (n = 4/7), and swallowing (n = 3/7). Individuals with SCA reported that all FARS-ADL items were relevant; Gait and Walking (n = 7/7), Bladder Function (n = 6/7), and Falling (n = 6/7) were considered extremely relevant. All HCPs (n = 8/8) reported that most FARS-ADL items were relevant to individuals with SCA; Quality of Sitting Position was considered least relevant. HCPs reported meaningful change as 1–2 point score change in individual FARS-ADL items (n = 7/7), 1–3 point change in total score (n = 6/6), and stability on any item and/or total score over ≥ 1 year, depending on SCA subtype (n = 5/8). Cognitive debriefing supported clarity and comprehension of FARS-ADL. Suggested improvements included refining response options for Dressing, Falling, Walking, and Bladder Function items. The findings confirm the content validity of most FARS-ADL items for use in individuals with mild-to-moderate SCA1 and SCA3, and offer suggested improvements for response options.