Creating a Disability Variable for Children with Disability Using the WHO ICF-CY Classification System

Aims: To create a single disability variable in 332 children with different disability severities, ICD-10 diagnoses, and ages by employing the WHO ICF-CY body functions coding system.

Study Design: Open field pilot research study.

Place and Duration of Study: H. C. Andersen Children’s Hospital and Centre for Clinical Epidemiology, Odense University Hospital, Odense Denmark, between October 2010 and November 2011.

Methodology: We included 332 children (144 boys and 188 girls; age range 1.0–15.9 years) with spina bifida, spinal muscular atrophy, muscular disorders, cerebral palsy, visual impairment, hearing impairment, mental disability, and disabilities following treatment for a brain tumour. A set of 47 body function codes (b codes) representing a broad spectrum of functions in daily living and with five qualifiers each was scored during interviews with parents. Psychometric and Rasch data analyses were performed.

Results: Mean code score for each child was 32.17 (range 0–159). The corrected code-total correlation was high (0.70). Inter-code correlation was mean 0.50 (range 0.01–0.97), and Cronbach´s alpha 0.98. Following Rasch analysis and due to disordering of Andrich thresholds (τs) and infit and outfit mean square values >1.5, the number of codes was reduced from 47 to 33. Retained codes all had ordered τs and mean square and corresponding Z-standardised values within the recommended range of 0.5–1.5. The t-statistic for differential item functioning across codes and diagnosis group, age, and gender was between 2.0 and 3.0. Graphical data for disability variable, the child-code map, paralleled clinical expectations across the total population of children.

Conclusion: WHO ICF-CY b codes can provide a coherent measure of the severity of disability in children across various diagnoses, age, and gender and add important information to WHO ICD-10 diagnosis codes when employed in daily clinical practice.