The Dyskinetic Cerebral Palsy Functional Impact Scale: development and validation of a new tool.

AIM To outline the development and examine the content and construct validity of a new tool, the Dyskinetic Cerebral Palsy Functional Impact Scale (D-FIS), which measures the impact of dyskinesia on everyday activities in children with cerebral palsy (CP). METHOD D-FIS content was informed by a systematic review of dyskinesia outcome measures, in collaboration with children with dyskinetic CP, parents, caregivers, and expert clinicians. The D-FIS uses parent proxy to rate impact of dyskinesia on everyday activities. Construct validity was determined by examining internal consistency; known groups validity with the Gross Motor Function Classification System (GMFCS), Manual Ability Classification System (MACS), Communication Function Classification System (CFCS), and Eating and Drinking Ability Classification System (EDACS); and convergent validity with the Barry-Albright Dystonia Scale (BADS). RESULTS Fifty-seven parents of children (29 males, 28 females, mean [SD] age 11y 8mo [4y 4mo], range 2y 6mo-18y) completed the D-FIS. Correlation between D-FIS and GMFCS was r=0.86 (95% confidence interval [CI]: 0.77-0.91, p<0.001); MACS r=0.84 (95% CI: 0.73-0.90, p<0.001); CFCS r=0.80 (95% CI: 0.67-0.88, p<0.001); and EDACS r=0.78 (95% CI: 0.66-0.87). Correlation between D-FIS and BADS was r=0.77 (95% CI: 0.64-0.86, p<0.001). Cronbach's alpha was 0.96. INTERPRETATION The D-FIS demonstrates good construct validity and high internal consistency. The D-FIS will be useful for identifying priorities for intervention. It adds to the measurement tool kit for children with dyskinetic CP by addressing functional impact of dyskinetic movements and postures.