Item hierarchy of the Chinese version of cerebral palsy quality of life for children

BackgroundThe Chinese Cerebral Palsy Quality of Life for Children (C CP QOL-Child) is the first instrument developed to measure quality of life of (QOL) children with cerebral palsy in Chinese speaking populations.ObjectiveThe aim of the study was to examine the psychometric properties of C CP QOL-Child using Item Response Theory Models. We were particularly interested to know how intervention strategies could be designed for individuals based on the item scores.Methods145 primary caregivers (mostly mothers; mean age: 39.2) of children with cerebral palsy aged 4–12 were invited to complete the 65-item C CP QOL-Child questionnaire. Data were analyzed using Rasch analysis.ResultsItem difficulty estimates were aligned with person ability values, indicating that the items in the scale generally demonstrated an appropriate depth and width for measuring QOL of persons in the target population. The results also showed that after dropping the 8 items in the dimension pain and impact of disability in the 65-item scale, the revised 57-item scale exhibits unidimensionality (separation index = 4.43, r = 0.95); hence the total score computed from the 57 items adequately reflects the level of QOL of the child as perceived by the caregiver. We further found that the Rasch item difficulty estimates demonstrated an overall item hierarchy; hence therapists can expect a pattern of performance by a child with CP that is based on the established order of item difficulty.ConclusionsThe hierarchical structure identified in the study may be useful for designing tailor-made interventions with an aim of improving QOL.