The micromeasurement of free erythrocyte protoporphyrin as a means of differentiating alpha thalassemia trait from iron deficiency anemia.

Free erythrocyte protoporphyrin levels were measured in 29 individuals with alpha thalassemia trait, 19 with proved iron deficiency anemia, and 25 normal control subjects. Individuals with alpha thalassemia trait and normal iron studies had FEP levels in the normal range despite marked degrees of microcytosis. In contrast, individuals with iron deficiency anemia had marked elevation of FEP levels with similar degrees of microcytosis. Measurement of FEP levels appears to be a useful tool in differentiating alpha thalassemia trait from iron deficiency anemia.