Assessment of data quality in a multi-centre cross-sectional study of participation and quality of life of children with cerebral palsy

1,174 children aged 8–12 years were selected from eight population-based registers of children with cerebral palsy; one further centre recruited 75 children from multiple sources. Families were visited by trained researchers who administered psychometric questionnaires. Logistic regression was used to assess factors related to family non-response and self-completion of questionnaires by children.431/1,174 (37%) families identified from registers did not respond: 146 (12%) were not traced; of the 1,028 traced families, 250 (24%) declined to participate and 35 (3%) were not approached. Families whose disabled children could walk unaided were more likely to decline to participate. 818 children entered the study of which 500 (61%) self-reported their quality of life; children with low IQ, seizures or inability to walk were less likely to self-report. There was substantial heterogeneity between regions in response rates and socio-demographic characteristics of families but not in age or gender of children. Item non-response was 2% for children and ranged from 0.4% to 5% for questionnaires completed by parents.While the proportion of untraced families was higher than in similar surveys, the refusal rate was comparable. To reduce bias, all analyses should allow for region, walking ability, age and socio-demographic characteristics. The 75 children in the region without a population based register are unlikely to introduce bias.SPARCLE [1] is a cross-sectional survey in nine European regions which examines the relationship between the physical, social and attitudinal environment of children with cerebral palsy and their participation in everyday activities and quality of life. Its analyses will take account of family stress and child behaviour. Children with cerebral palsy were studied because they often have impairments of learning, hearing, vision, communication and epilepsy in addition to motor impairment and so are more representative of disabled children than a group w