Improvement of SF-36 scores in cervical dystonia patients-Is there a treatment effect when evaluating subscales?

BackgroundTo evaluate treatment effects of abobotulinumtoxinA in cervical dystonia (CD) using multilevel modelling and beta-binomial regression on different dimensions of the Short-Form-36 (SF-36) health-related quality-of-life questionnaire.MethodsThis study involved a post hoc analysis of patient-reported outcomes (PROs) from a Phase III, double-blind, randomised, placebo-controlled multicentre trial that had evaluated abobotulinumtoxinA's efficacy in patients with CD, including assessment using the SF-36 at baseline and 8 weeks. Multilevel modelling was used to explore between-centre and between-patient variability in these outcomes. In addition, the outcomes were assessed using beta-binomial regression, since this provides a good fit with the non-normal distribution of SF-36 data and allowed all eight health domains to be analysed by a single method.ResultsCompared with placebo, abobotulinumtoxinA produced significant improvement in the physical health component of SF-36 from baseline to week 8. Reduction in the physical health component score was associated with patients' age (p = 0.008), being male (p = 0.009) and investigator's visual analogue scale for symptoms (p = 0.006). The abobotulinumtoxinA group was 1.6 times more likely than the placebo group to show improvement in the physical functioning domain (p = 0.01). Significant improvements for the role-emotional and mental health domains were 2.4 (p = 0.0001) and 1.5 times (p = 0.007) more likely with abobotulinumtoxinA than with placebo.ConclusionsAbobotulinumtoxinA's clinical efficacy in relieving symptoms of CD is associated with significant HRQoL benefits. Compared with placebo, abobotulinumtoxinA therapy is associated with statistically significant improvements at week 8 on the physical health component of SF-36, as well as in the physical functioning, role-emotional and mental health domains.