The reasoning: large cells need a smear-based split
Megaloblastic anaemia reflects impaired DNA synthesis, producing macro-ovalocytes, hypersegmented neutrophils and ineffective haematopoiesis. LDH and indirect bilirubin may rise because precursors die in the marrow. Non-megaloblastic macrocytosis includes alcohol, liver disease, hypothyroidism, reticulocytosis, drugs and myelodysplastic neoplasms.