Measurement of physical function in childhood-onset facioscapulohumeral dystrophy

Facioscapulohumeral dystrophy (FSHD) is a rare slowly progressive autosomal dominant muscular dystrophy. Distinctive facial weakness and scapular winging are early signs of the disease. Muscle weakness progresses in a cephalocaudal direction affecting muscles of the trunk, pelvis, and lower limbs in an often, profoundly asymmetrical pattern. A younger age at onset of symptoms is thought to be associated with increased disease severity and a faster rate of progression. The low incidence of childhood-onset FSHD has limited collection of longitudinal natural history data and impaired development of disease-specific outcome measures suitable for children. These key knowledge gaps have impacted development of paediatric specific clinical practice guidelines and limited paediatric clinical trial design. This thesis, comprising four sub-studies, aimed to better understand available standardised measures of physical function and determine their appropriateness for use in children and adolescents with FSHD. A review identified instruments used to evaluate physical function in published research studies and critically appraised their measurement properties. Two subsequent studies evaluated reliability, validity and longitudinal utility of a novel disease-specific outcome measure identified in the review. Measurement properties of the FSHD-Composite Outcome Measure and paediatric version (FSHD-COM Peds) were evaluated in children and adolescents with FSHD. Finally, a survey asked clinicians working in FSHD care, to identify outcome measure instruments used and barriers to non-use in their clinical practice. Research revealed the small array of low-quality instruments available to evaluate physical function in general, and a shortage of instruments suitable for children and non-ambulant individuals with FSHD. The potential for the FSHD-COM Peds to successfully measure function in children is supported by excellent intra rater test re-test reliability, good convergent and discri