Occurrence of lead poisoning during follow-up of children at risk with initial screening lead blood levels below 100 μg/L

Background. - Follow-up is recommended for children initially screened with a lead blood level below the threshold for lead poisoning of 10 mu g/dL when they have one or more risk factors. At first, the frequency of a follow-up lead blood test was calculated in children at risk for lead poisoning. In second time, we calculated the rate of occurrence and independent factors for lead poisoning in the follow-up group. Methods. - Since 1992, the Greater Paris lead poisoning monitoring system (SSSIILF) has been systematically recording data on lead levels in blood tests conducted for screening and follow-up in Greater Paris. Children initially screened before the age of seven whose blood lead level was inferior to 10 mu g/dL and who had one or more risk factors were selected. The association between qualitative variables and a follow-up lead blood test was compared using the Chi(2) test. For children given follow-up, the association between qualitative variables and occurrence of lead poisoning was compared using the Chi(2) test; independent factors for lead poisoning were estimated by logistic regression. Results. - A follow-up lead blood test was more frequent and the difference was statistically significant, for children with one or more of the following risk factors identified at the time of screening: home address in Seine Saint-Denis or central Paris, screened in mother/child healthcare centers (PMI) or through a private physician, a blood lead level 5 mu g/dL on initial screening, young age (< 24 months) at the time of screening and some others known risk factors. The rate of occurrence of lead poisoning during follow-up was 25.9% for children screened between 1992 to 1994 and decrease to 5.1% for children screened in 2004 to 2005 (p < 0.001) and was lower in central Paris and Seine Saint-Denis than in other districts in Greater Paris (p < 0.01). The rate of occurrence during follow-up, independent of known risk factors for lead poisoning (p < 0.01), was higher for children screened before the age of two (p < 0.01) and for children whose mothers were from Sub-Saharan Africa (p < 0.01). Conclusion. - It is essential to follow up children at risk with an initial lead blood level below 10 mu g/dL, especially those initially screened before the age of 24 months. Local action on home environment could also be needed when the initial blood lead level is 5 mu g/dL and more than one risk factor has been identified. (C) 2009 Elsevier Masson SAS. All rights reserved.