Using unstimulated urinary lead excretion to assess the need for chelation in the treatment of lead poisoning.

To determine whether unstimulated urine samples could be used to identify children needing chelation therapy for lead poisoning, we compared urinary lead excretion with and without chelation. A convenience sample of 39 children was admitted to a pediatric clinical research center for therapeutic chelation. Urine was collected for 24 hours on 2 consecutive days. Edetate disodium calcium, 1000 mg/m2, was given intramuscularly in two divided doses on the second day. Significant correlations existed between urinary lead excretion (PbU) on the control day at 12- and 24-hour collection intervals and on the first day of chelation (p less than 0.0001). Published criteria for positive edetate disodium calcium provocative tests were used to calculate corresponding cutoff points for unstimulated 24-hour PbU. Resultant PbU values ranged from 10.4 to 35.6 micrograms (0.05 to 0.17 mumol). When PbU was expressed in terms of creatinine excretion, cutoff points of 0.06 and 0.19 microgram PbU/mg creatinine were determined, making possible the use of random unstimulated samples to assist in the identification of children in need of chelation.