Macrocytic Anemia: The Workup

The workup for macrocytic anemia should include some or all the following:

• Peripheral blood smear
  • Hypersegmented neutrophils and macroovalocytes → B12 or folate deficiency.
  • Pancytopenia → advanced B12 deficiency
  • Target cells → chronic liver disease (anemia and thrombocytopenia are also seen).
  • Pseudo-Pelger-Huët cells → myelodysplastic syndrome.
• For vitamin B12 deficiency
  • Vitamin B12 levels
  • Methylmalonic acid and LDH → high in vitamin B12 deficiency
  • Liver chemistry studies → elevated LDH and unconjugated bilirubin further support the diagnosis of B12 deficiency
• Serum folate level → folate deficiency

  

• Markers of hepatic insufficiency
  • CBC (for anemia, thrombocytopenia)
  • Albumen and
  • Prothrombin time
  • Liver chemistry studies may help as well
• TSH: if hypothyroidism is suspected
• Prealbumin → malnutrition (important cause of macrocytic anemia)
• Reticulocyte count → hemolysis or recovery from blood loss anemia. (Immature red blood cells tend to be larger than mature red blood cells.)
• Serum ethanol level → alcoholism. Actually, you seldom need this test because the patient history is often sufficient. I just put it here to remind me (and you!) that ethanol consumption is the most common cause of macrocytosis in Western countries. In addition, many other toxins also cause macrocytosis, including sulfa drugs, methotrexate, azathioprine and zidovudine.

• Board Basics 3 (2012, reviewed here)
• Fischer, Conrad, MD, Master the Boards: Internal Medicine (2013)
• Sabatine, Marc S., MD, MPH, Pocket Medicine, 5e (2014)
• Haematology, A Core Curriculum (2010, reviewed here)