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

BACKGROUND

Follow-up is recommended for children initially screened with a lead blood level below the threshold for lead poisoning of 10 microg/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 microg/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 microg/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 microg/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 microg/dL and more than one risk factor has been identified.