Clinical Question: Does treatment for lead exposure affect neurologic development in children?
Study Design: Randomized controlled trial (double-blinded)
Synopsis: The authors enrolled 780 children, 12 to 33 months of age, with a blood lead level between 20 and 44 mcg per dL (0.97 to 2.12 μmol per L). After the level of lead was confirmed, the children were randomized to receive placebo or succimer in a dosage of 1,050 mg per m2 per day for seven days, and then 700 mg per m2 per day for 19 additional days. Two weeks after the completion of therapy, the children who still had elevated blood lead levels were treated for up to two more courses. The homes of all of the children were cleaned, and paint was stabilized as necessary to prevent continued lead exposure. Children were evaluated three years after treatment and again at seven years of age using the Developmental Neuropsychological Assessment, the Wechsler Scales of Intelligence, the Conners’ Parent Rating Scale–Revised, and other tests.
Six months after treatment, blood lead levels were an average 4.5 mcg per dL (0.22 μmol per L) lower in the treated group; 12 months after treatment, blood lead levels were 2.7 mcg per dL (0.13 μmol per L) lower. By the time the children reached seven years of age, the blood levels were similar in both groups (8.0 mcg per dL [0.39 μmol per L]), with a similar proportion of children in both groups having a blood lead concentration greater than 10 mcg per dL (0.48 μmol per L). However, in the 83 percent of children evaluated at seven years of age, no difference was noted between the groups on any of the 12 neuropsychologic outcomes, which is concordant with other findings three years after treatment (Liu X, et al. Do children with falling blood lead levels have improved cognition? Pediatrics October 2002;110:787–91).
Bottom Line: Among children with elevated blood lead levels, drug treatment reduces those levels, although the children’s intelligence, cognition, and other neurodevelopment markers are the same at seven years of age as those of children whose homes were made free of lead but who did not receive medication. These findings support guidelines that do not recommend chelation therapy in children with blood lead levels of less than 45 mcg per dL (2.17 μmol per L; United States Centers for Disease Control and Prevention Guidelines, 2002). (Level of Evidence: 1b)