Free erythrocyte porphyrin: hemoglobin ratios, serum ferritin, and transferrin saturation levels during treatment of infants with iron-deficiency anemia.

Free erythrocyte porphyrin:hemoglobin (FEP:Hb) ratios were determined on 20 infants with iron-deficiency anemia. FEB:Hb ratios were compared with simultaneously drawn serum ferritin and serum transferrin saturation levels. FEP:Hb ratios dropped steadily during treatment of the anemic infants, but remained elevated compared to age-matched nonanemic infants, until the anemia was corrected. FEP:Hb ratios detected iron deficiency when acute inflammatory disease was present. Serum ferritin levels and transferrin saturation failed to detect iron deficiency after iron therapy was started or when acute inflammatory disease was present. Measurement of FEP:Hb ratios is a reliable and practical way to make a prompt diagnosis of iron-deficiency anemia in infants.