Ataxia at first assessment predicts four-year functional outcomes
Worse ataxia anticipates poor prognosis in people with Friedreich’s ataxia
Worse ataxia at an initial assessment predicted poor outcomes after four years in people with Friedreich’s ataxia (FA), according to a natural history study.
The speed of disease progression was different, fastest in those in the earliest disease stages and gradually slowing as it advanced. Being younger at the evaluation was also associated with a faster rate of ataxia progression. Gait was affected earlier in the disease course and had the highest annual progression rate.
The study, “Longitudinal changes of SARA scale in Friedreich ataxia: Strong influence of baseline score and age at onset,” was published in the Annals of Clinical and Translational Neurology.
Studying Friedreich’s ataxia natural history
FA is an inherited, progressive disease marked by loss of control of body movements (ataxia). It typically begins in childhood or adolescence, with walking difficulties as a common early symptom. People with FA usually need a wheelchair within 10 years of the onset of symptoms and may be completely incapacitated by middle age.
Two large observational studies were set up to better understand the disease’s natural history — how a disease progresses without treatment — and to define reliable outcome measures for potential therapies.
The European Friedreich’s Ataxia Consortium for Translational Studies (EFACTS; NCT02069509) includes 18 sites in Europe and the Friedreich’s Ataxia-Clinical Outcome Measures Study (FA COMS; NCT03090789) is collecting data from patients in the U.S., Canada, and Australia.
In this report, scientists in Europe examined EFACTS data to assess changes in patients’ functional abilities over time. The Scale for the Assessment and Rating of Ataxia (SARA) was used to assess on gait (walking), stance, sitting, speech disturbance, and limb coordination.
Among the 502 patients, (ages 6-68), 266 were women, with an age of onset from 1-24 and a disease duration of 1-55 years. SARA assessments were conducted at enrollment (baseline) and each year for four years.
At recruitment, 30% of participants already scored at the highest SARA values (31-40), with scores ranging from 0 (no ataxia) to 40 (most severe ataxia).
Mean SARA scores slowly increased from 23.4 at baseline to 26.9 at the four-year follow-up. At the same time, mode values, the most frequent values in the dataset, remained constant.
“The observation that the mean value gradually increased with time with the mode value remaining stable suggests a systematic difference in progression between patients with SARA score below and above 24-25 points,” the researchers wrote.
Over four years, total SARA scores for each patient showed a linear relationship (steady increase) with disease progression. A relationship between baseline SARA total score and time indicated the annual progression rate depended on baseline SARA scores.
The most rapid progression occurred in those with the lowest scores. Participants with baseline scores between 0-5 increased by about 2 points a year compared with those with baseline scores of 35-40, who showed a progression of 0.1 points per year. A younger age at onset was associated with a higher progression rate.
Differences in progression rates
The annual progression rate varied significantly between patients.
Consistent with total scores, the progression rate for individual items in the SARA assessment was highest for low baseline scores. For example, the maximum annual progression rate for gait was 0.84 points for a baseline score of 0 and it decreased to 0.12 points for a baseline score of 7.
Gait had the maximum annual progression rate, whereas speech and finger-chase items showed the lowest rates. For gait and stance, a 1-point change occurred after about a year of disease duration, while the median time to score change ranged between two and four years for the remaining items.
“Gait and stance not only are affected earlier in the course of the disease, but also their score progresses more rapidly than the other items,” the scientists noted. “The analyses of temporal [time-based] dynamics of the [SARA] scale and its items may provide further insights of relevant factors to be taken into account for population selection and result interpretation in future clinical trials.”
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