Should we screen for lead poisoning after 36 months of age? Experience in the inner city.

Abstract

Current lead screening guidelines recommend monitoring lead levels in children under 3 years of age. There are, however, a number of children between the ages of 3 and 6 years who have elevated blood lead levels. Whether these lead elevations are new or chronic has not been examined. To determine the proportion of children with lead levels greater than or equal to 10 microg/dL after their third birthday when all prior testing had been normal. Retrospective study based on 39000 venous lead tests obtained between 1993 and 1998. From this group, 2046 children were located who had blood lead levels of less than 10 microg/dL before 36 months and who had a follow-up lead level after 36 months. All lead assays were done by the City of New York laboratories, which had an intrasample variability of 13%. Sixty-six (3.2%) of the 2046 children showed an elevation in blood lead for the first time after their third birthday. The abnormal values ranged from 10 to 25 microg/dL. The majority (72%) of the screen-positive children, however, had lead levels of 10 to 12 microg/dL, and 63.3% of screen-positive children with repeat tests had lead levels that reverted to below 10 microg/dL. The data indicate that some new cases of lead level elevations did occur after 3 years of age in this 'high-risk' community; however, the current study provides evidence that universal screening for lead poisoning beyond 3 years of age is not warranted in this community as it is not likely to pick up clinically important exposure.