Patient selection:
(1) Children should have an initial blood level from 25-44 µg/dL.
(2) Children with lead levels < 25 µg/dL are unlikely to respond to the test dose of EDTA with a lead diuresis.
(3) Children with levels >= 45 µg/dL should not have the test performed. They should be referred for chelation therapy immediately.
(4) Iron status can affect the outcome of the test. The test should not be done if the child is iron deficient.
Procedure:
(1) The child is instructed to empty the urinary bladder.
(2) 500 mg per square meter BSA of calcium disodium ethylenediaminetetracetic acid (CaNa2 EDTA) is administered in 5% dextrose as an infusion over 1 hour.
(3) The urine is collected for 8 hours in lead-free containers. The final volume is measured.
(4) An aliquot is sent in a lead-free container for lead determination. It should be kept at 20°C until the lead concentration is measured.
lead excreted in µg =
= (lead in µg/dL) * (volume of urine in mL) / 100 mL/dL
lead excretion ratio =
= (lead excreted in µg) / (dose of CaNa2-EDTA given in mg)
Interpretation:
• The test is considered positive if the ratio is > 0.6 (some use > 0.5), or if the total urinary excretion is > 200 µg in 8 hours.
• Children with a blood lead level of 25-44 µg/dL and a positive mobilization test should undergo a 5-day course of chelation therapy.
• If the lead level is < 25 µg/dL, then the patient should be followed clinically and removed from further lead exposure.
Limitations:
• The test is typically done only at medical centers having a large number of children with lead poisoning due to the staff and time requirements for accurate specimen collection.
• If the containers are not lead free, falsely elevated values may occur.
