Measuring socio-economic inequalities in the presentation of injuries to a paediatric A&E department: the importance of an epidemiological approach.

OBJECTIVES To contrast the socio-economic pattern of childhood injuries presenting to a paediatric accident and emergency (A&E) department revealed by using both a numerator-based and a denominator-based approach to the analysis of injury surveillance data. METHODS Injury surveillance data collected during 1997-1998 at a Glasgow children's hospital A&E department were analysed. Socio-economic status was measured using Carstairs' deprivation index. Data from West Glasgow postcode sectors only were analysed in order to optimize epidemiological validity. Socio-economic patterning of injury was investigated in two ways-numerator-based and denominator-based. RESULTS A total of 12,762 children (0-14 years) living in West Glasgow attended the A&E department of the Royal Hospital for Sick Children over the study period. Both analytical approaches showed a clear and statistically significant excess of injury presentations in children from more deprived postcode sectors, but the variation appeared much greater in the numerator-based rather than the denominator-based approach. In regression analysis, however, only the denominator-derived rates showed a statistically significant linear trend across deprivation categories. CONCLUSION The most appropriate and accurate means of measuring the extent of socio-economic (and other) inequalities in injury risk is to adopt a population-based rather than numerator-based perspective on the data collected by injury surveillance systems.