A longitudinal study of the SF-36 version 2 in Friedreich ataxia

The Medical Outcomes Study 36 item Short-Form Health Survey (SF-36) is one of the most commonly used patient reported outcome measure. This study aimed to examine the relationship between SF-36 version 2 (SF-36V2) summary scores and Friedreich ataxia (FRDA) clinical characteristics, and to investigate the responsiveness of the scale, in comparison with the Friedreich Ataxia Rating Scale (FARS), over 1, 2 and 3 years.

Descriptive statistics were used to examine the characteristics of the cohort at baseline and years 1, 2 and 3. Correlations between FRDA clinical characteristics and SF-36V2 summary scores were reported. Responsiveness was measured using paired t tests.

We found significant correlations between the physical component summary (PCS) of the SF-36V2 and various FRDA clinical parameters but none for the mental component summary. No significant changes in the SF-36V2 were seen over 1 or 2 years; however, PCS scores at Year 3 were significantly lower than at baseline (-3.3, SD [7.6], P=.01). FARS scores were found to be significantly greater at Years 1, 2 and 3 when compared to baseline.

Our findings suggest that despite physical decline, individuals with FRDA have relatively stable mental well-being. This study demonstrates that the SF-36V2 is unlikely to be a useful tool for identifying clinical change in FRDA therapeutic trials.