OPPORTUNISTIC SAMPLING FROM EARLY-CHILDHOOD CENTERS - A SUBSTITUTE FOR RANDOM SAMPLING TO DETERMINE LEAD AND IRON STATUS OF PRESCHOOL-CHILDREN

This report compares the results from two sampling strategies used to determine the prevalence of elevated blood lead concentrations and iro n status in 12-36 month old children in Central Sydney.The two methods were stratified random sampling using census collector districts and an opportunistic sampling strategy using client registers at Early Chi ldhood Centres (ECCs).The response rates were 75.3% (n=718 of whom 198 were aged 12-36 months) and 24.1% (n=304) respectively. The geometric mean blood lead concentrations were 0.40 and 0.34 mu mol/L respective ly (p=0.001). The traditional random sampling prevalence survey identi fied a significantly higher proportion of children with blood lead con centrations greater than 0.48 (OR=0.61, 95% CI 0.40-0.93) and 0.72 mu mol/L (OR=0.44, 95% CI 0.21-0.92) compared to the simpler opportunisti c survey. The median plasma ferritin concentration for both studies wa s 19 mu g/L (p=0.4). The prevalence of iron depletion, iron deficiency and iron deficiency anaemia was not significantly different between t he two studies. In conclusion, opportunistic sampling through ECCs doe s not appear to be a substitute for the traditional random sampling pr evalence surveys to determine the prevalence of elevated blood lead co ncentrations in preschool children in Central Sydney. However, opportu nistic sampling through ECCs may be an appropriate method for monitori ng iron status, in particular iron depletion, in pre-school children i n Central Sydney.