Objective: Our study aims to assess the acceptability, validity and responsiveness of the EQ-5D-3L in SCA types 1, 2, 3 and 6.

Background: Although health-related quality of life (HRQoL) becomes an essential outcome parameter in clinical trials and the decision-making field of treatments [1,2], evidence about the psychometric performance of the HRQoL measure – EQ-5D-3L – in SCA 1, 2, 3 and 6 is inconclusive. We have performed analyses based on the classical test theory to obtain a valid picture of the EQ-5D-3Ls applicability in that disease group.

Method: The analysis was based on data from two prospective, longitudinal cohort studies with predominantly European SCA patients. Patients completed a set of health questionnaires at baseline and several annual follow-ups, assessing the EQ-5D-3L and EQ-VAS, the Scale for Assessment and Rating of Ataxia (SARA), Activities of Daily Living (ADL) as part of Friedreich´s ataxia rating scale, the Inventory of Non-Ataxia Signs (INAS) and the Patient Health Questionnaire (PHQ-9). EQ-5D-3L comprises five items to compute a health index (EQ-5D_Index) and consists of a visual analogue scale to measure general health (EQ_VAS). We analysed terms of acceptability (missing values), distribution properties, discriminative ability to distinguish between different health states, convergent validity (Spearman correlation coefficients) and effect size measures to examine health changes regarding ataxia severity.

Results: We analysed 842 SCA patients (mean age 49.9 ±13.7 years, female: 49%). Item non-response of the EQ-5D_Index was 0.8% and of the EQ_VAS 3.4%. Ceiling effects occurred in 9.9% (EQ-5D_Index) and 3.0% (EQ_VAS) with a mean EQ-5D_Index of 0.65±0.21. The EQ-5D_Index has been significantly differentiated between different stages of age, ataxia severity (SARA), limitations of ADL, INAS and PHQ-9. EQ-5D_Index and EQ_VAS show moderate to strong correlations with SARA (SARA_EQ-5DIndex=-0.562; SARA_EQVAS=-0.396), ADL (ADL_EQ-5DIndex=-0.713; ADL_EQVAS=-0.507), INAS (INAS_EQ-5DIndex=-0.381; INAS_EQVAS=-0.329) and PHQ-9 (PHQ-9_EQ-5DIndex=-0.474; PHQ-9_EQVAS=-0.453). Analysis of health change shows small effect sizes.

Conclusion: Subjective health states of SCA-patients can be adequately measured with the acceptable and valid EQ-5D-3L and besides well-established clinical ataxia instruments. Further HRQoL ataxia research is necessary, focused on health economic evaluations and treatment.

References: 1. Calvert M, Kyte D, Duffy H, Gheorghe A, Mercieca-Bebber R, Ives J, et al. Patient-reported outcome (PRO) assessment in clinical trials: a systematic review of guidance for trial protocol writers. PloS one. 2014;9(10):e110216.
2. Scoggins JF, Patrick DL. The use of patient-reported outcomes instruments in registered clinical trials: evidence from ClinicalTrials.gov. Contemporary clinical trials. 2009;30(4):289-92.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/validation-of-the-eq-5d-3l-in-spinocerebellar-ataxia-sca/