Need for the lead mobilization test in children with lead poisoning.

We evaluated the recommendation of the Centers for Disease Control, that children with moderate lead poisoning undergo the lead mobilization test (LMT) to determine the need for a full course of chelation treatment. Current criteria for selection for this test include a blood Pb concentration (bPb) between 25 and 55 micrograms/dl and an erythrocyte protoporphyrin level greater than 35 micrograms/dl. To determine whether the eligibility criteria could be refined to a smaller group of patients, we compared bPb determinations obtained on the day of the LMT in 198 children with moderate Pb poisoning to the results of the LMT. We found that children with bPb less than 25 micrograms/dl were unlikely to respond to the test dose of calcium disodium ethylenediamine tetraacetate with a Pb diuresis (24/25 patients had low urinary Pb excretion on the LMT). In contrast, 88% of children with bPb greater than or equal to 40 micrograms/dl were likely to excrete sufficient Pb to indicate the need for a full course of chelation. We conclude that the LMT is indicated for children with bPbs between 25 and 40 micrograms/dl. Children with bPb between 40 and 55 micrograms/dl may receive chelation therapy without having an LMT, if the performance of the LMT is not practical. Patients with levels less than 25 micrograms/dl should be followed clinically and removed from further Pb exposure.