Diagnostic status, functional status and complexity among Canadian children with neurodevelopmental disorders and disabilities: a population-based study.

PURPOSE: To identify and describe selected key characteristics of children with neurodevelopmental disorders and disabilities (NDD/D) in a national disability survey database.
METHOD: Secondary analysis of data on children aged 5-14 years in the Canadian Participation and Activity Limitation Survey (PALS). Children with NDD/D were ascertained from ICD-10 diagnoses "fine-tuned" with functional limitation information, and classified into six predetermined NDD/D subtypes by independent expert evaluators.
RESULTS: Children with NDD/D accounted for 73.5% of children with disabilities. Amongst children with a single NDD/D type, 28.8% were in the Cognition-Learning subgroup, 22.2% Psychological, 19.9% Social interactive, 13.3% Sensory, 10.6% Motor and 5.2% Speech-Language disorders/disabilities. Complexity, both diagnostic (more than one ICD-10 diagnosis) and functional (more than one parent-identified functional limitation), was encountered frequently though variably across NDD/D subtypes. In aligning parent-identified functional limitation information with researcher-ascertained assignment of children to NDD/D subgroups, matching with additional limitations (61.3% of children) occurred far more commonly than simple 1:1 matches (14.0%) or non-matching (24.7%).
CONCLUSIONS: Conceptual, definitional and terminology issues affect population-based research on children with NDD/D. Ascertainment methods can use diagnostic as well as functional information. Diagnostic information alone is likely to under-represent the complexity and needs of children with NDD/D and their families.