Which laboratory finding is most characteristic of megaloblastic anemia due to vitamin B12 or folate deficiency?

Which laboratory finding is most characteristic of megaloblastic anemia due to vitamin B12 or folate deficiency?

• A. Low RBC count
• B. Low B12/folate
• C. Normal MCHC
• D. Low Platelet count

Answer: (B)

Megaloblastic anemia from B12 or folate deficiency arises because these nutrients are essential for DNA synthesis in developing red cells. When they’re lacking, the cells can’t mature properly, leading to macrocytosis and ineffective erythropoiesis. The most characteristic laboratory finding is directly measuring the deficiency itself—low serum vitamin B12 or low serum folate. This identifies the root cause of the abnormal red cell production and explains the macrocytic picture. Other findings like a low red blood cell count or a low platelet count can occur due to overall marrow suppression, and MCHC is often normal, but these are less specific than the direct deficiency.

Megaloblastic anemia from B12 or folate deficiency arises because these nutrients are essential for DNA synthesis in developing red cells. When they’re lacking, the cells can’t mature properly, leading to macrocytosis and ineffective erythropoiesis. The most characteristic laboratory finding is directly measuring the deficiency itself—low serum vitamin B12 or low serum folate. This identifies the root cause of the abnormal red cell production and explains the macrocytic picture. Other findings like a low red blood cell count or a low platelet count can occur due to overall marrow suppression, and MCHC is often normal, but these are less specific than the direct deficiency.