Which of the following is a diagnostic finding for Vitamin B12 deficiency anemia?

A diagnostic finding for Vitamin B12 deficiency anemia is indicated by an elevated mean corpuscular volume (MCV), which is greater than 100 fL. Vitamin B12 deficiency leads to impaired DNA synthesis, causing the production of larger than normal red blood cells, known as macrocytes. This change in red blood cell size is a hallmark of megaloblastic anemia, which includes Vitamin B12 deficiency as one of its most common causes.

While decreased hemoglobin can be present in various types of anemia, including Vitamin B12 deficiency, it is not specific to this condition; it can also occur in iron deficiency anemia and other forms of anemia. Elevated serum ferritin is typically a finding in iron storage disorders or anemia of chronic disease rather than Vitamin B12 deficiency. A high white blood cell count is not expected in vitamin deficiency anemias and can indicate other underlying conditions or responses in the body, but it does not serve as a diagnostic criterion for Vitamin B12 deficiency anemia.