Relative anemia and iron deficiency in cystic fibrosis

Significant alterations in hemotologic function in cystic fibrosis are suggested by the observation that polycythemia is uncommon, even among cyanotic patients. To elucidate those factors that influence hematologic equilibrium, 39 stable patients with cystic fibrosis were evaluated with regard to hemoglobin, hematocrit, RBC indices, reticulocyte count, serum iron and total iron binding capacity, serum ferritin, vitamin E, and carboxyhemoglobin levels. Hemoglobin concentrations were below the 50th percentile for age in 90% of the patients, including the 23% who were cyanotic. Serum ferritin levels were below the mean for age in 85% and below 12 ng/mL in 33% of patients. Vitamin E levels were less than 5 micrograms/dL in 33%, indicating deficiency. Carboxyhemoglobin values were elevated in 64% of the patients. These data indicate that relative anemia is common in cystic fibrosis and suggest that iron and vitamin E deficiency may contribute to that anemia. Twenty-two patients with cystic fibrosis were then given 2 weeks of oral iron therapy followed by two to three additional weeks of iron and vitamin E. This therapeutic trial resulted in an increase in mean hemoglobin concentration from 13.87 to 14.50 g/dL (P less than 0.01) associated with a significant increase in levels of serum ferritin (P less than 0.001). The increase in hemoglobin occurred primarily during the second 2 weeks when patients were receiving both iron and vitamin E. However, we were unable to document evidence of increased hemolysis when patients were receiving iron therapy alone. This response to oral iron therapy is confirmation that iron deficiency contributes to the failure of some patients with cystic fibrosis to compensate hemotologically for hypoxia.