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Dr Snow¹ is right that the diagnosis of vitamin B₁₂ or folate deficiency is no longer as straightforward as it once seemed. Although his review of available tests is useful, I must take issue with some of his assertions.

His list of nonmegaloblastic causes of macrocytic anemia fails to include the most common cause (especially in an elderly population), myelodysplastic disorders, particularly sideroblastic anemia. (Contrary to the classification in some textbooks, most acquired sideroblastic anemias are macrocytic overall.²) The inclusion of myelodysplastic disorders in the differential diagnosis of macrocytic anemia highlights other reasons for utility of the peripheral blood smear; findings such as dimorphic red blood cells, anisochromia, and pseudo–Pelger-Huët neutrophils can point to an alternative diagnosis to vitamin B₁₂ or folate deficiency. Patients with macrocytic anemias have been inappropriately admitted and subjected to blood transfusion and extensive laboratory tests for rare hemolytic disorders because the basics of the . . . [Full Text of this Article]

THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES

Food Cobalamin Malabsorption: A Usual Cause of Vitamin B12 Deficiency
Andres et al.
Arch Intern Med 2000;160:2061-2062.
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