The Scale for Assessment and Rating of Ataxia (SARA) score progression may be dependent on baseline score and age at onset for patients with Friedreich ataxia (FA), according to a study published in Annals of Clinical and Translational Neurology.
During the study, the progression rate of SARA scores appeared to depend on baseline SARA scores, where patients with lower SARA scores had faster score changes than those with higher SARA scores at baseline.
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The annual progression rate ranged from 2 points for lower baseline scores (between 0 and 5 points) to 0.1 of a point for higher baseline scores (>30 points). Modeling indicated a decrease in the annual progression rate of .058 points for each point in the baseline score.
“Analyses of statistical properties of SARA suggest a variable sensitivity of the scale at different disease stages and provide important information for population selection and result interpretation in future clinical trials,” the authors wrote.
The researchers mentioned that the variability in progression rate might suggest a nonlinear progression for the disease. However, the SARA progression was substantially linear over the 4-year interval of the study.
The SARA scores were not normally distributed at either baseline or during the 4-year follow-up period, and many patients already had high SARA scores at baseline (around 30 points), with some individual items already at their maximum values. To account for the nonnormal distribution, the SARA progression rates were calculated using the scores at enrollment as continuous covariates.
Separate analyses found that age at evaluation and age at onset also were correlated with SARA score progression. Age at onset appeared to be more predictive than age at evaluation, however. FA disease duration was also investigated but did not appear to be correlated with the rate of SARA score progression.
Analysis of individual items within the SARA score showed a similar pattern of higher progression rate at lower values and slower progression at higher baseline values.
A total of 502 participants with typical-onset FA (age <25 at onset) who were participating in the European FA Consortium for Translational Studies longitudinal study were included in the current study. The median age of patients at baseline was 29 years, and roughly half (52.9%) were female. Data was collected from 11 clinical sites across Europe.
Porcu L, Fichera M, Nanetti L, et al. Longitudinal changes of SARA scale in Friedreich ataxia: Strong influence of baseline score and age at onset. Ann Clin Transl Neurol. Published online August 28, 2023. doi:10.1002/acn3.51886