Longitudinal Assessment for Lead Poisoning

Abstract

In a previous study, we showed that in our region the prevalence of lead poisoning (Pb ≥ 10 μg/dL [0.483 μmol/L]) was high (29%) among urban infants. The objectives of this study were to assess the prevalence of lead poisoning over time in this cohort to determine the best screening strategy. Eighty nine percent (115/129) of infants who were initially screened for lead poisoning between 6 and 12 months of age had a repeat venous lead level by age 3 years (χ=19.8 months). The majority (70%) lived in a major city and had private medical insurance (80%). The initial and repeat mean venous lead levels were similar for the overall population (lead₁ = 8.7 μg/dL ± 6.2 [0.420 ± 0.299 μmol/L] and lead2 = 7.7 μg/dL ± 6.8 [0.371 ± 0.328 μmol/L]). However, the percentage of lead-poisoned (Pb ≥ 10 μg/dL or 0.483 μmol/L) children whose levels were ≥15 μg/dL (0.724 μmol/L) increased from 28% to 48% on repeat. The utility of the initial screen in predicting a second elevated lead level ≥20 μg/dL (0.966 μmol/L) was as follows: sensitivity = 33%, specificity = 97%, positive predictive value = 40%, negative predictive value = 96%. We conclude that in this population, a single screen at 18-24 months of age would reduce the need for multiple venipunctures and would detect those children in need of an intervention.