672 CaNa₂EDTA PROVOCATIVE TESTS (EPT's) IN CHILDREN WITH MILD-MODERATE INCREASED LEAD (Pb) ABSORPTION

Abstract

Screening programs for Pb poisoning emphasize measurements of blood Pb and erythrocyte protoporphyrin (EP). A far more sensitive index of the size of chelatable and potentially toxic Pb stores, the EPT, has yet to be evaluated in children with mild-moderate increased lead absorption. EPT's were performed in 20 such children: 4 CDC Class II (Pb 30-49μg/dl, EP 50-109μg/dl) and 16 in Class III, who were further subdivided: IIIa (Pb 30-49μg/dl, EP > 110μg/d1) and IIIb (Pb 50-69μg/dl, EP>50μg/dl). CaNa₂EDTA (500 mg/m²/dose) was given q 12 H × 2, and the 24-hour urinary Pb (^uPb) excretion was measured. A positive EPT was defined as urinary excretion of Pb ≥ 500μg/24H.

Conclusions: 1) Measurements of blood Pb and/or EP are imprecise indicators of chelatable Pb, as determined by the EPT, in children with mild-moderate increased Pb absorption; 2) 70% of all children in this study required 5 days of treatment for increased Pb absorption; 3) Based on conventional screening tests, these children may have gone untreated; 4) We suggest that all children with blood Pb>30 and EP>50 should have careful assessment of the size of chelatable Pb stores by a precise method, namely, the CaNa₂EDTA provocative test.

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