RESUMO
We evaluated the recommendation of the Centers for Disease Control, that children with moderate lead poisoning undergo the lead mobilization test (LMT) to determine the need for a full course of chelation treatment. Current criteria for selection for this test include a blood Pb concentration (bPb) between 25 and 55 micrograms/dl and an erythrocyte protoporphyrin level greater than 35 micrograms/dl. To determine whether the eligibility criteria could be refined to a smaller group of patients, we compared bPb determinations obtained on the day of the LMT in 198 children with moderate Pb poisoning to the results of the LMT. We found that children with bPb less than 25 micrograms/dl were unlikely to respond to the test dose of calcium disodium ethylenediamine tetraacetate with a Pb diuresis (24/25 patients had low urinary Pb excretion on the LMT). In contrast, 88% of children with bPb greater than or equal to 40 micrograms/dl were likely to excrete sufficient Pb to indicate the need for a full course of chelation. We conclude that the LMT is indicated for children with bPbs between 25 and 40 micrograms/dl. Children with bPb between 40 and 55 micrograms/dl may receive chelation therapy without having an LMT, if the performance of the LMT is not practical. Patients with levels less than 25 micrograms/dl should be followed clinically and removed from further Pb exposure.
Assuntos
Intoxicação por Chumbo/diagnóstico , Chumbo/urina , Quelantes/uso terapêutico , Criança , Pré-Escolar , Ácido Edético , Eritrócitos/química , Estudos de Avaliação como Assunto , Humanos , Lactente , Chumbo/sangue , Intoxicação por Chumbo/tratamento farmacológico , Intoxicação por Chumbo/metabolismo , Protoporfirinas/sangueRESUMO
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 micrograms/dl and who had erythrocyte protoporphyrin concentrations greater than or equal to 35 micrograms/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 less than 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 micrograms. 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.
Assuntos
Anemia Hipocrômica/urina , Intoxicação por Chumbo/urina , Chumbo/urina , Anemia Hipocrômica/sangue , Anemia Hipocrômica/complicações , Criança , Pré-Escolar , Ácido Edético , Ferritinas/sangue , Humanos , Lactente , Intoxicação por Chumbo/sangue , Intoxicação por Chumbo/complicações , Valor Preditivo dos Testes , Protoporfirinas/sangueRESUMO
Twenty-four-hour CaNa2EDTA provocative tests for the assessment of lead stores were successfully performed in 36 asymptomatic children with mild to moderate undue lead absorption (blood lead concentration less than or equal to 69 micrograms/dl and erythrocyte protoporphyrin greater than or equal to 50 micrograms/dl). By comparing lead excretion during the first 8 hours with that excreted during the entire 24-hour test, new criteria have been developed to define positive outcomes. We suggest that the excretion of greater than or equal to 200 micrograms lead per 8 hours or a ratio of urinary lead (micrograms)/CaNa2EDTA administered (mg) greater than or equal to 0.70 after a single intramuscular injection of CaNa2EDTA (500 mg/m2) can identify those children who will respond to chelation treatment with lead diuresis.