Children with Moderately Elevated Blood Lead Levels: A Role for Other Diagnostic Tests?

Abstract

JSTOR is a not-for-profit service that helps scholars, researchers, and students discover, use, and build upon a wide range of content in a trusted digital archive. We use information technology and tools to increase productivity and facilitate new forms of scholarship. For more information about JSTOR, please contact support@jstor.org.. The National Institute of Environmental Health Sciences (NIEHS) and Brogan & Partners are collaborating with JSTOR to digitize, preserve and extend access to Environmental Health Perspectives.In this study we examined potential limitations of relying exclusively on blood lead (BPb) levels to evaluate children with moderately elevated BPb levels (1.21-2.12 pamol/l, or 25-44 lig/dl). We tested the following hypotheses: 1) such children without elevated erythrocyte protoporphyrin (EP) levels (>0.62 pmol/l or >35 pg/dl) are unlikely to respond to a chelating agent with a brisk urinary Pb diuresis; 2) those with elevated EP levels, but low hematologic indices consistent with iron deficiency, are also unlikely to respond to a chelating agent with a robust urinary Pb diuresis; and 3) those with elevated EP levels and iron sufficiency are more likely to respond to a chelating agent. To test these hypotheses, we performed retrospective analyses of the relationships between EP concentrations, hematologic indices, and urinary Pb excretion ratios (uPbr) in moderately Pb-poisoned children undergoing the CaNa2EDTA lead mobilization test (Pb-MT). Data from 122 children were available. Urinary Pb excretion was limited in children with an EP <0.62 plmol/l (<35 pg/dl); only 5% (1/21) of Pb-MTs were positive (uPbr >0.6). In children with an EP >0.62 limol/l, low hematologic indices, such as a mean corpuscular hemoglobin (MCH) <23 pg, were associated with relatively little Pb excretion (0/14 positive Pb-MTs). In contrast, 32% (28/87) of Pb-MTs were positive in children with an EP >0.62 pmol/l and iron sufficiency (p<0.01 by chi-square comparison between groups with EP >0.62 plmol/l and either MCH <23 pg or MCH >23 pg). We conclude that only a minority of moderately Pbpoisoned children will demonstrate enhanced urinary Pb excretion in response to chelation therapy. Some of the predicted nonresponders can be readily identified by adding the EP and complete blood count to the panel of tests performed. Key words: blood lead levels, chelation, erythrocyte protoporphyrin, iron deficiency, lead diagnosis, lead mobilization test, lead poisoning, urine lead.Learn how to responsibly manage the by-products of health care as part of your commitment to a healthy community.Dedicated to the memory of Karen Wetterhahn, a medical researcher who died 10 months after being exposed to one drop of dimethyl mercury.For information, call 800-639-3188 or visit our web site: http://uvmce.uvm.edu:443/profprog.htm

Iron Deficiency in Children: Detection and Prevention

“…If in doubt, the blood lead levels should be determined and the response to iron noted. Lead diuresis and reduction in blood lead following chelation treatment are less in iron‐deficient children (Ruff et al , 1996; Markowitz et al , 1997).…”