Interaction of Iron Deficiency and Lead and the Hematologic Findings in Children With Severe Lead Poisoning

Abstract

Microcytic anemia, long considered an effect of lead poisoning, may in fact result from coexisting iron deficiency. In this study, how RBC size, hemoglobin, and zinc protoporphyrin vary as a function of iron status in a group of children with high lead levels was examined. Charts of all children (N = 51) admitted to Cook County Hospital for treatment of lead poisoning in 1981 to 1983 were reviewed for data on age, blood lead level, hemoglobin concentration, MCV, transferrin saturation and zinc protoporphyrin level. The mean lead level was 86 µg/dL and the range was 63 to 190 µg/dL. Children with transferrin saturation values less than 7% had a mean MCV of 56 pµL, hemoglobin of 8.9 g/dL, and zinc protoporphyrin of 693 µg/dL; for those with saturations of 7% to 16%, the values were 61 µL, 10.1 g/dL, and 581 µg/dL, respectively; the children with saturations greater than 16% had normal mean MCVs and hemoglobin concentrations (74 µL and 11.4 g/dL) and a mean zinc protoporphyrin value of 240 µg/dL (P < .0005). Multiple linear regression was used to correct for effect of age, and transferrin saturation remained the most important predictor of MCV, hemoglobin, and zinc protoporphyrin levels; the addition of lead did not improve the models. Results of this study suggest that iron deficiency is strongly associated with some of the observed toxicities of lead. Also, lead poisoning can exist without producing microcytosis or anemia, and zinc protoporphyrin concentration may not be a sensitive indicator of lead level in the absence of iron deficiency.