Serum ferritin in assessment of iron nutrition in healthy infants.

We followed up 238 infants on 7 occasions during their first year of life. The diets of the infants were systematically either supplemented or not supplemented with iron. Developmental changes in serum ferritin were determined from a group with adequate intake of iron and without evidence of iron deficiency by three laboratory criteria: hemoglobin, mean corpuscular volume and transferrin saturation. The data indicate that the average level of serum ferritin correlates well with iron nutrition within groups of infants since the developmental changes are in accordance with the known changes in storage iron, the level of serum ferritin correlates with iron intake, and low ferritin levels are associated with lower transferrin saturation. The usefulness of serum ferritin as the sole criterion of iron deficiency in individual infants is limited, suggesting the use of more than one indicator to refine the diagnosis of iron deficiency without anemia.