Procedure:
(1) Instruct the child to empty the urinary bladder.
(2) Collect a 24 hour urine in a lead free container.
(3) Measure the volume in mL.
(4) Submit an aliquot for lead and creatinine determination, storing at 20°C until analysis.
24 hour urinary lead excretion in µg =
= (urinary lead concentration in µg/dL) * (urine volume in mL) / (100 mL/dL)
24 hour urinary creatinine excretion in mg =
= (urinary creatinine concentration in mg/dL) * (urine volume in mL) / (100 mL/dL)
lead-to-creatinine ratio =
= (24 hour urinary lead excretion in µg) / (24 hour urinary creatinine excretion in mg)
Interpretation:
• A ratio of > 0.19 µg lead per mg creatinine indicates the need for chelation therapy.
• Children with a ratio > 0.06 should be evaluated on the basis of their age, duration of lead elevation and history of previous chelation. Many of these children should have chelation therapy.
