885 FREE ERYTHROCYTE PROTOPORPHYRIN IN SICKLE CELL ANEMIA

Abstract

We recently conducted a screening program to determine the incidence of iron deficiency in 66 patients with sickle cell disease. We found mean free erythrocyte protoporphyrin (FEP) values of 168 μg/dl RBC in 50 HbSS patients in contrast to 81 μg/dl RBC in 16 HbSC patients and 60 μg/dl RBC in 9 normals. Six of the pts with sickle cell disease had iron deficiency anemia documented by response to iron. None of the sickle cell patients had evidence for lead poisoning. FEP in iron deficient HbSS patients was 308 μg/dl RBC, and in iron sufficient HbSS patients was 153 μg/dl RBC. The correlation between FEP and retic count was excellent (p<.001). Reticulocyte rich fractions prepared by stractan density gradient separation from HbSS, hereditary spherocytosis, and pyruvate kinase deficient RBC samples had 40% higher FEP levels than reticulocyte poor fractions. Spectrofluorometric analysis of red cell protoporphyrin extracted in acetone-acetic acid revealed a four-fold increase in the ratio of protoporphyrin IX/zinc-protoporphyrin in reticulocyte rich fractions compared to normal or reticulocyte poor fractions. We found iron deficiency in 26% of non-transfused sickle cell patients. Our FEP results suggest that elevated reticulocyte counts contribute to high FEP values in HbSS patients and that the protoporphyrin distribution in reticulocytes differs from that in mature erythrocytes. We suggest that if FEP is used to screen for iron deficiency in HbSS patients that the FEP value be adjusted for the reticulocyte count. Supported by NHLB Grant No. HL 20985-2 from NIH.