| Predicting the Outcome of the CaNa2EDTA Challenge Test in Children with Moderately Elevated Blood Lead Levels James R. Campbell and Stanley J. Schaffer Department of Pediatrics, University of Rochester School of Medicine and Dentistry, Rochester, New York, USA Abstract
The Centers for Disease Control and Prevention suggests the challenge test for children whose blood lead levels are 1.21-2.12 µmol/L (25-44 µg/dL) . However, the challenge test is difficult to perform. By identifying children who are likely to have a negative challenge test, a medical provider can minimize the number of children undergoing this test. The goal of this study was to identify common tests that are likely to predict the outcome of the challenge test. It was conducted as a clinical descriptive study from a series of patients who underwent a CaNa2EDTA challenge test. Results from 178 challenge tests were eligible for analysis. The mean age of children undergoing the challenge test was 38.2 months, and the mean blood lead level was 1.83 µmol/L (38 µg/dL) . Blood lead level, age, erythrocyte protoporphyrin level, and RATE (a measure of the rate of change of the blood lead level) were either not sensitive or not specific in predicting the outcome of a challenge test. However, based on a logistic regression model using blood lead level, age, and RATE, we determined criteria that would have identified all children who would have had a positive challenge test while excluding most children who would have had a negative challenge test. Based on this model, we recommend that the challenge test be conducted on children  36 months of age who have a blood lead level between 1.45 and 1.64 µmol/L (30-34 µg/dL) and on children who have a blood lead level 1.69-2.12 µmol/L (35-44 µg/dL) regardless of age. This approach would have tested all children who subsequently would have had a positive challenge test while testing only 39% of children who would have had a negative challenge test. Key words: calcium disodium edetate, challenge test, chelation, lead toxicity. Environ Health Perspect 107:437-440 (1999) . [Online 21 April 1999] http://ehpnet1.niehs.nih.gov/docs/1999/107p437-440campbell/ abstract.html Address correspondence to J.R. Campbell, Department of Pediatrics, Rochester General Hospital, MOB Suite 300, 1425 Portland Avenue, Rochester, NY 14621-3095 USA. Telephone: (716) 338-4028. Fax: (716) 336-3929. E-mail: JAMES.CAMPBELL@VIAHEALTH.ORG We thank C. Burton and C. Asfoury for assistance in chart review and data entry, and M. Weitzman for reviewing the manuscript. This manuscript was presented, in part, at the Annual Meeting of the Society for Pediatric Research on 3 May 1997 in Washington, D.C. Received 31 August 1998 ; accepted 26 January 1999.
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