Planche et al outlined a work-up of a patient with extreme macrocytosis. The authors are from multiple hospitals in Paris.
Patient selection: MCV >= 130 fL, with or without anemia
Parameters for the initial work-up:
(1) drug history (HAART, hydroxyurea, valproic acid, phenytoin, isoniazid, trimethroprim/sulfamethoxazole, atovaquone/proguanil, methotrexate, sunitinib, cyclophosphamide, azathioprine, other)
(2) anemia status
(3) red blood cell morphology
(4) serum vitamin B12 concentration
(5) serum folate concentration
(6) history of chronic alcoholism
(7) reticulocytosis
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Finding
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Next Step
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hydroxyurea or HAART without anemia
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no further evaluation recommended
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anemia and reduced vitamin B12
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consider causes of vitamin B12 deficiency
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anemia and reduced folate, normal vitamin B12
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look for evidence of chronic alcohol abuse
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anemia and reticulocytosis
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work-up for hemolytic anemia; look for schistocytes in the peripheral blood smear; perform DAT
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associated cytopenias or uncertain cause
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consider bone marrow exam; consider myelodysplasia; consider hypothyroidism; carefully re-examine the blood smear
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Work-up for vitamin B12 deficiency:
(1) pernicious anemia (anti-intrinsic factor antibodies, anti-parietal cell antibodies)
(2) atrophic gastritis
(3) Helicobacter pylori
(4) drugs (proton pump inhibitors, meformin)
(5) gatrectomy
(6) dietary deficiency
