Developing and Validating the GMPM
Development and validation of an instrument to measure gross motor performance for evaluation of treatment outcomes in cerebral palsy
This project was designed to investigate the validity, reliability and responsiveness of the Gross Motor Performance Measure (GMPM). The GMPM is an observational instrument used to evaluate gross motor performance (i.e., quality of movement) in children with cerebral palsy. The instrument's primary purpose is to evaluate change over time in specific qualitative features or attributes of gross motor behaviour. The measure was found to be responsive to change over time.
Physical therapists from 3 children's treatment centres assessed 107 children with CP, 18 children with head injury and 33 children without physical disabilities. Assessments were conducted on 2 occasions, 4 to 6 months apart. The measurement protocol included assessment with the GMPM and the Gross Motor Function Measure (GMFM). Validity was tested by comparing changes in GMPM scores to parent and therapist independent ratings of the children's motor performance. Also, a sample (n=30) of paired assessments was videotaped for "masked" evaluation by therapists. Inter-rater, intra-rater and test-retest reliability studies (n=30) were conducted. Responsiveness to change was determined through parent and therapist ratings of the importance of observed changes in quality of movement.
Inter-rater, intra-rater and test-retest reliabilities were calculated using intra-class correlations, and
these were found to be high (0.93, 0.97 and 0.96, respectively). Several a priori hypotheses supported the GMPM's construct validity however relationships with parent and therapist judgements of change were not clearly demonstrated. The measure was found to be differentially responsive to changes in "stable" and "responsive" groups.
The GMPM is useful in evaluating change over time in the quality of a child's motor behaviour.
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