Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (288 page)

   Microcytic

   Macrocytic

   Normocytic

   Aplastic

   Hemoglobinopathies

   Hemolytic anemias

   Sickle cell

   HbC, HbD, HbE diseases

   Thalassemias

Suggested Readings

Beutler E, Waalen J. The definition of anemia: what is the lower limit of normal of the blood hemoglobin concentration?
Blood.
2006;107:1747−1750.

Tefferi A. Anemia in adults: a contemporary approach to diagnosis.
Mayo Clin Proc.
2003; 78:1274−1280.

MACROCYTIC ANEMIAS

   Definition

Anemias in which the RBCs are oval macrocytes, with an MCV larger than normal (>101 fL).

   Who Should Be Suspected?

A patient with macrocytic anemia, hypersegmented neutrophils on peripheral blood smear, and symptoms of malabsorption, poor diet, chronic hemolysis without folate supplementation, chemotherapy, or hypothyroidism. Folate deficiency is seen with alcoholism; in third-world countries, it may be associated with sprue-like syndromes. Vitamin B
₁₂
(cobalamin) deficiency increases in incidence with aging, and should be searched for, even in the absence of anemia in the elderly with neurologic deficits. Cobalamin and folic acid deficiencies often coexist. Other causes of macrocytic anemias are liver cirrhosis, myelodysplastic syndrome (MDS), azidothymidine (AZT) therapy for AIDS, Down syndrome, and normal newborns.

   Laboratory Findings

Laboratory investigation of macrocytic anemias must differentiate between macrocytic anemias without megaloblastosis and true megaloblastic anemias resulting from vitamin B
₁₂
and/or folate deficiency. Megaloblastic anemia is a morphologic definition based on bone marrow examination. B
₁₂
deficiency may be the result of pernicious anemia (PA) (lack of intrinsic factor) or may have other etiologies.