Evaluation of Anemia.

Anemia is a common problem in primary care. Classification based on mean cell volume narrows the differential diagnosis and directs testing. A marked macrocytosis is characteristic of vitamin B12 and folate deficiencies, certain medications, and primary bone marrow disorders. The three most common causes of microcytic anemia are iron deficiency, thalassemia trait, and anemia of inflammation. Additional laboratory testing is required for diagnosis. Determination of the rate of development of anemia and examination of a blood smear may provide diagnostic clues to guide more specialized testing. Diagnosis of iron, vitamin B12, or folate deficiency mandates determination of the underlying cause.