Construct validity and responsiveness of Movakic: An instrument for the evaluation of motor abilities in children with severe multiple disabilities

Movakic is a newly developed instrument for measurement of motor abilities in children with severe multiple disabilities, with a satisfactory feasibility and content validity and good inter-observer and test-retest reliability. The objective of this study was to investigate its construct validity and responsiveness to change. Sixty children with severe multiple disabilities (mean age 7.7 years, range 2-16) were measured using Movakic six times during 18 months. Construct validity was assessed by correlating Movakic scores with expert judgment. In order to assess responsiveness, scores during 3-months intervals were compared (mean score-changes and intraclass correlations) during which some children experienced meaningful events influencing motor abilities and during which others experienced no such event. Forty-five percent of children had a lower cognitive development level than 6-month, 52% had Gross Motor Function Classification System level V and 37% had level IV. For 27 children all measurements were completed, six children dropped out. Construct validity was good (r=0.50-0.71). Responsiveness was demonstrated by significantly larger score changes after events than when such events did not occur. Movakic is a valid instrument for measuring motor abilities in children with severe multiple disabilities. Results suggest responsiveness to change in motor abilities after meaningful events.