Assessment of upper limb capacity in children with unilateral cerebral palsy: construct validity of a Rasch-reduced Modified House Classification.

AIM The aim of this study was to test and improve the unidimensionality and item hierarchy of the Modified House Classification (MHC) for the assessment of upper limb capacity in children with unilateral cerebral palsy (CP) using Rasch analysis. The construct validity of the Rasch-reduced item set was evaluated. METHOD Modified House Classification items were scored from 369 videotaped assessments of 159 children with unilateral CP (98 males, 61 females; median age 6y 6mo, range 2y 1mo-17y 5mo). Construct validity was tested in 40 other children with unilateral CP (21 males, 19 females; median age 8y 2mo, range 3y 3mo-17y 6mo) by comparing total scores with the Manual Ability Classification System (MACS) and the ABILHAND-Kids scale. RESULTS Fifteen MHC items could be included in the Rasch analysis. The excluded items were either too easy or too difficult. Fourteen items fitted the unidimensional model (χ(2) =41.3, df=39, p=0.37). The hierarchy of these items was different from the original MHC. There was a significant correlation with the MACS (r=-0.901, p<0.001) and the ABILHAND-Kids scale (r=0.558, p<0.001). INTERPRETATION The original item hierarchy of the MHC can be improved in order to use its sum score for the assessment of upper limb capacity in children with unilateral CP. The Rasch-reduced 14-item MHC with weighted sum score shows good construct validity to measure functional capacity of the affected hand in children with unilateral CP.