Provocation chelation test

Blood lead levels provide the best indicators of lead poisoning but do not reflect total body burden (Lee and Moore 1990). The inhibition of erythrocyte 8-aminolevulinic acid indicates lead exposure, but most centers still use blood lead levels for screening (Lee and Moore 1990 Roper et al. 1993 Schaffer and Campbell 1994). Zinc protoporphyrin indicates neurotoxicity from lead but does not have the sensitivity for assessing low levels of exposure (Anger and Johnson 1985 Royce and Needleman 1995). Radiological examination of the abdomen and long bones does not reliably portray exposure. The same holds true for the examination of red blood cells for basophilic stippling and the assay of hair and nail levels for lead (Roper et al. 1993). The Centers for Disease Control and Prevention (CDC) does not recommend use of scarification of the forearm with 25% sodium sulfite solution to assess for black discoloration of skin, a procedure recommended in some sources. Medical centers perform an edetate disodium calcium provocative chelation test with urinalysis and complete blood... 

An additional test may be given if the child s blood lead-level is over 20 p.g/dl but below 45 p-g/dl, the level at which pharmacological treatment is clearly recommended by the CDC. Some practices will use a mobilization test (or provocation chelation test) to help determine the best course of treatment for the child. A drug is given to the child and the urine is colleeted for a number of hours afterwards. The amount of lead which is excreted in the urine will be an indication of the effectiveness of the drug in removing lead from the child s blood. This information is used in combination with other factors to decide whether to treat the child with a course of this drug. ... 

Lead-exposed children Provocative chelation testing using CaN2 EDTA at lower, subtherapeutic doses Logarithmic relationship, chelatable to PbB nonsymptomatic children show chelation plumburesis similar to that in lead-poisoned ones Chisolm et al. (1976), Saenger et al. (1982)... 

Because the onset of lead poisoning usually is insidious, it often is desirable to estimate the body burden of lead in individuals who are exposed to an environment that is contaminated with the metal. In the past, the edetate calcium disodium (CaNaJlDTA) provocation test was used to determine whether there is an increased body burden of lead in those for whom exposure occurred much earlier. The provocation test is performed by intravenous administration of a single dose of CaNa DTA (50 mg/kg) followed by collection of urine for 8 hours. The test is positive for children when the lead excretion ratio (pg of lead excreted in the urine per mg of CaNa DTA administered) is >0.6 it also may be useful for therapeutic chelation in children with blood levels of 25 5 pg/dL. This test is not used in symptomatic patients or in those whose concentration of lead in blood is >45 pg/dL because these patients require the proper therapeutic regimen with chelating agents (see below). 

Past exposure to lead, which is not necessarily reflected by elevated PbB levels, can be estimated by measuring the amount of lead excreted in urine after provocation with a chelating agent, e.g. EDTA (Alessio et al., 1979). If, after administration of 1 g EDTA, the amount of lead in urine exceeds 1 mg in 24 h, the test usually Is considered positive (Lauwerys, 1983). Measurement of lead in hair allows the estimation of exposure during the previous months. Although hair is an easily available material, this method may not be reliable because It is highly difficult to distinguish between lead Incorporated into the hair and that simply adsorbed on its surface. 

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