Background: For children with asymptomatic moderate lead poisoning (Blood lead level [BPb] 25 to 55 micrograms/dL [1.21 to 2.66 mumol/L]), treatment with the chelating agent calcium disodium versenate (CaNa2EDTA) is recommended for all those children with a BPb level > 45 micrograms/dL (2.17 mumol/L) and for those with a BPb level of 25 to 44 micrograms/dL (1.21 to 2.13 mumol/L) who also have a positive lead mobilization test. However, controlled studies demonstrating its efficacy at inducing a sustained reduction in BPb level or lead-related toxicity have not been performed in children with moderate lead poisoning. This study assesses the relationship between CaNa2EDTA chelation and measures of lead burden and toxicity in children with moderate lead poisoning.
Methods: Two hundred one children with moderate lead poisoning were enrolled. Sequential changes in BPb concentrations, bone lead level as measured by L alpha-x-ray fluorescence, and lead-induced toxicity as assessed by erythrocyte protoporphyrin levels were determined over a 7-week period. From this group, children with a positive lead mobilization test received CaNa2EDTA chelation therapy.
Results: Children with positive lead mobilization tests had on average higher initial BPb, bone lead, and erythrocyte protoporphyrin concentrations. The chelated children decreased approximately 4.7 micrograms/dL (0.23 mumol/L), 41 corrected net counts, and 24 micrograms/dL (0.46 mumol/L) more than the unchelated children on BPb, bone lead, and erythrocyte protoporphyrin values, respectively. However, children with higher initial levels decreased the most, whereas children with lower initial levels showed the least decline, with or without treatment. When the initial values on the measures were controlled analytically, or when subgroups matched on initial levels were compared, there were no significant differences between the chelated and unchelated children.
Conclusions: The apparent effectiveness of CaNa2EDTA at reducing lead burden and toxicity is no longer observed when the pretreatment levels are considered. The findings suggest that sufficient doubt about CaNa2EDTA efficacy now exists to warrant a randomized controlled trial of chelation therapy in moderately lead-poisoned children. However, until such studies are performed, it would be premature to withhold chelation treatment on the basis of this study alone.