Which test can help determine the cause of B12 anemia?

The Schilling test is a specific diagnostic test used to determine the cause of vitamin B12 deficiency anemia. It assesses the absorption of vitamin B12 in the gastrointestinal tract and helps differentiate between pernicious anemia, which results from an intrinsic factor deficiency, and malabsorption syndromes.

In this test, a small amount of radioactive vitamin B12 is administered, along with intrinsic factor. Then, urine is collected to measure the amount of vitamin B12 excreted. If the uptake is low, the diagnosis may suggest pernicious anemia caused by lack of intrinsic factor, while normal absorption indicates a different cause of B12 deficiency.

Other tests listed, while useful in assessing anemia, do not specifically determine the cause of B12 deficiency. A Complete Blood Count can show changes in red blood cell indices associated with anemia but does not specify the type or cause. A bone marrow biopsy might help assess causes of anemia at the marrow level but is more invasive and not specific for B12 deficiency. The serum ferritin test evaluates iron stores and can identify iron deficiency anemia but does not provide information on vitamin B12 levels or absorption, confirming its suitability for assessing different types of anemia.

The Schilling test remains the most targeted tool for diagnosing vitamin B12 absorption