Clinical evaluation of a lead mobilization test using the chelating agent dimercaptosuccinic acid.

Hoet, Perrine [UCL] Buchet, Jean-Pierre [UCL] Decerf, Laurence [UCL] Lavalleye, Benoît [UCL] Haufroid, Vincent [UCL] Lison, Dominique [UCL]

BACKGROUND: The lead mobilization test reflects the mobilizable and likely toxicologically active fraction of the lead body burden. We propose a safe and convenient protocol for this test, to assess concomitant copper and zinc excretion and to determine the size of the chelatable lead pool in nonoccupationally exposed adults. METHODS: The study population included 80 white adults: 40 controls [median blood lead concentration (PbB), 25 microg/L] and 40 lead-exposed individuals (315 microg/L). After collection of 4- and 24-h baseline urine specimens and a blood sample, dimercaptosuccinic acid (DMSA) was administered orally (1 g), and additional 4- and 24-h urine specimens were obtained. Determinants of the chelatable urinary lead (DMSA-PbU) were traced by linear regression analysis. RESULTS: Urinary DMSA and lead excretion peaked within 2-3 h after DMSA administration. The amounts of DMSA, lead, copper, and zinc recovered in the 4-h urinary collections were highly correlated with those in 24-h collections (r = 0.857, 0.859, 0.958, and 0.757, respectively). At PbB concentrations >300 microg/L, the relationship between DMSA-PbU and PbB showed a steep increase and a widespread dispersion of DMSA-PbU around the regression line. After DMSA, copper and zinc excretion rates were increased up to 91- and 33-fold, respectively. No side effects were reported after DMSA. CONCLUSIONS: Determination of DMSA-PbU in a 4-h collection after DMSA is convenient, apparently safe, and inexpensive. An upper reference limit value of 22 microg/4 h is proposed for Belgian reference individuals. The diagnostic value of DMSA-PbU is likely to be contributive for PbB >300 microg/L.