OP60 – 2351: Reliability and discriminant validity of ataxia rating scales in early onset ataxia

Abstract

Objectives In children and young adults, Early Onset Ataxia (EOA) is frequently concurrent with other movement disorders, resulting in moderate inter-observer agreement among movement disorder professionals. To investigate whether phenotypic steps are replaceable by quantitative measures, we aimed to determine inter-observer agreement and discriminant validity of ataxia rating scales. Methods In 40 EOA patients (15 (5–34) years; mean (range)), three independent pediatric neurologists assessed quantitative ataxia rating scales (ICARS, SARA and BARS), and phenotyped the primary movement disorder characteristic (i.e. ataxic, dystonic, myoclonic, chorea, tics) in each patient. We determined inter- and intra-observer agreement and specified outcomes for “primary” (i.e. primary ataxia identification by all assessors and/or identified ataxic diagnosis (n=26)) and “secondary” (i.e. incomplete identification of ataxia as the primary movement disorder (n=12)) subgroups. Results Inter- and intra-observer agreement of ataxia rating scales revealed high intra-class correlation coefficients (ICC: 0.92–0.99; for ICARS, SARA and BARS), with no significant differences between “primary” and “secondary” subgroups. Total ataxia rating scale scores revealed higher outcomes in the “primary” than the “secondary” subgroup (p Conclusions In EOA, quantitative rating scales reveal high inter- and intra-observer reliability, reflecting reliable applicability. However, multivariable regression analysis revealed low discriminant validity between ataxia and other movement disorder characteristics. Despite high reliability of quantitative ataxia scores, these data implicate that preceding phenotypic characterization remains irreplaceable.