OBJECTIVE: To develop a Rasch-based version of a mobility questionnaire (MobQues28) for children with cerebral palsy (CP). DESIGN: Cross-sectional study. SETTING: Private physical therapy practices and outpatient departments of hospitals and rehabilitation centers. PARTICIPANTS: Parents of 323 ambulatory children with CP (Gross Motor Function Classification System [GMFCS] level I-IV; aged, 2-13y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The mobility questionnaire measures mobility limitations in children with CP by rating the difficulty of executing 47 mobility activities, as reported by the parents. Items for the Rasch-based version were selected based on fit to the Rasch measurement (partial credit) model and invariance of item characteristics across GMFCS level, age group, or sex. RESULTS: Analysis revealed a fitting model when nonambulant and/or 2- and 3-year aged children were excluded (leaving a final sample of n=246) and answering categories were collapsed from 9 to 5. Thirteen items were removed from the questionnaire due to misfit to the model, 5 because of disordered thresholds, and 1 because of invariance across age group. Twenty-eight items out of the original 47 items showed good fit to the model. CONCLUSIONS: The 28-item version of the mobility questionnaire (MobQues28) provides sound measurement properties for measuring mobility limitations in ambulant children with CP, aged 4 to 13 years, and shows promise as an instrument for research purposes.
OBJECTIVE: To develop a Rasch-based version of a mobility questionnaire (MobQues28) for children with cerebral palsy (CP). DESIGN: Cross-sectional study. SETTING: Private physical therapy practices and outpatient departments of hospitals and rehabilitation centers. PARTICIPANTS: Parents of 323 ambulatory children with CP (Gross Motor Function Classification System [GMFCS] level I-IV; aged, 2-13y). INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The mobility questionnaire measures mobility limitations in children with CP by rating the difficulty of executing 47 mobility activities, as reported by the parents. Items for the Rasch-based version were selected based on fit to the Rasch measurement (partial credit) model and invariance of item characteristics across GMFCS level, age group, or sex. RESULTS: Analysis revealed a fitting model when nonambulant and/or 2- and 3-year aged children were excluded (leaving a final sample of n=246) and answering categories were collapsed from 9 to 5. Thirteen items were removed from the questionnaire due to misfit to the model, 5 because of disordered thresholds, and 1 because of invariance across age group. Twenty-eight items out of the original 47 items showed good fit to the model. CONCLUSIONS: The 28-item version of the mobility questionnaire (MobQues28) provides sound measurement properties for measuring mobility limitations in ambulant children with CP, aged 4 to 13 years, and shows promise as an instrument for research purposes.