A Patient-Reported Measure of Locomotor Function Derived from the Functional Assessment Questionnaire

BackgroundLocomotor function is often impaired in children diagnosed with cerebral palsy (CP). Improving locomotor function is a common goal of treatment. The current gold standard for assessing locomotor function in CP is the gross motor function measure (GMFM-66). The GMFM-66 requires an in-person assessment by a trained clinician. It would be useful to have a measure of function that is like the GMFM-66 but can be assessed through patient report. MethodsWe queried the clinical databases of two motion analysis centers (Gillette Childrens Specialty Healthcare and Shriners Hospital - Salt Lake City) for individuals with a diagnosis of cerebral palsy (CP) who were 18 years old or younger and had undergone instrumented clinical gait analysis that included the functional assessment questionnaire (FAQ). We computed the transformed FAQ (FAQt) as the weighted sum of the skills an individual was able to perform, where the weighting was the difficulty of the skills. We assessed concurrent and external validity of the FAQt by comparing it to the GMFM-66. ResultsThe FAQt exhibited strong concurrent and external validity. Linear regression showed that the GMFM-66 explained 54% of the variance in FAQt, and the linear fit was independent of center. The FAQt evolved with age in a manner similar to the GMFM-66, with higher functioning individuals, as measured by gross motor function classification system level, achieving higher levels of function at a higher rate and an earlier age compared to their lower functioning peers. The findings with respect to GMFM-66 did not depend on the center at which the data was acquired. ConclusionsThe FAQt demonstrates strong concurrent and external validity, making it a useful measure of locomotor function.