Determining the cause of anemia. General approach, with emphasis on microcytic hypochromic anemias.

In the vast majority of cases, the cause of microcytic hypochromic anemia is clearly suggested by the patient history, physical examination results, red cell indexes, and peripheral blood smear. Thus, further diagnostic testing, if necessary, can be very selective. When the underlying cause of anemia is obscure, the serum ferritin concentration should be measured first. If it is normal or increased, serum iron and free erythrocyte protoporphyrin levels can be determined. The serum iron level is low in anemias caused by iron deficiency and chronic disease but normal or elevated in those resulting from the thalassemias, hemoglobin E disorders, and lead toxicity. The free erythrocyte protoporphyrin level is elevated with iron deficiency, the anemia of chronic disease, and lead toxicity but normal with thalassemias and hemoglobin E disorders. Results of these two test indicate which of the more specific tests is most likely to yield the correct diagnosis.