Effects of iron deficiency on lead excretion in children with moderate lead intoxication

The effect of iron status on calcium disodium edetate (CaNa₂EDTA)-induced lead diuresis was examined in 112 children with moderate lead intoxication. Patients whose blood lead levels were between 25 and 55 μg/dl and who had erythrocyte protoporphyrin concentrations ≥35 μg/dl underwent provocative testing to determine the need for a full course of chelation therapy. A blood sample for lead, erythrocyte protoporphyrin, and serum ferritin determinations was obtained immediately before the intramuscular administration of CaNa₂EDTA, 500 mg/m². Determination of urinary lead level was based on an 8-hour urine collection. Blood lead and ferritin levels were significantly correlated with urinary lead excretion: r=0.542 and 0.298, respectively, p<0.01 for both. Multiple regression models were tested to assess the independent effects of the variables. With blood lead level controlled, ferritin remained significantly associated with urinary lead excretion; for every 1 ng/ml increase in ferritin, urinary lead increased by 2.4 μg. This small effect of ferritin on urinary lead was illustrated in a discriminant analysis. Using blood lead level by itself as the independent variable resulted in a 76% correct assignment of provocative test outcomes. Knowing the ferritin level improved this assignment accuracy by only 3%. We conclude that the iron status, as measured by serum ferritin, of children with moderate lead intoxication, has a small but significant effect on CaNa₂EDTA-induced lead diuresis. This effect may influence the interpretation of borderline provocative test outcomes. Although chelation therapy should not be withheld pending treatment of iron deficiency, lead stores should be reassessed after iron repletion.