Which diagnostic test may be positive in pernicious anemia?

Which diagnostic test may be positive in pernicious anemia?

• A. Coombs test
• B. Schilling test
• C. G6PD assay
• D. ANA titer

Answer: (B)

Pernicious anemia is B12 deficiency caused by lack of intrinsic factor from autoimmune destruction of stomach parietal cells. The Schilling test was historically used to determine whether B12 malabsorption is intrinsic factor–dependent. In the first stage, radiolabeled B12 is given orally and the amount excreted in the urine is measured; in pernicious anemia this excretion is low because intrinsic factor is absent. The test is repeated in a second stage with intrinsic factor added; if the urinary excretion normalizes, it confirms that the malabsorption was due to intrinsic factor deficiency. So the Schilling test would yield a positive finding by showing abnormal B12 absorption that corrects with intrinsic factor, pointing to pernicious anemia. The other tests listed assess different conditions (Coombs for autoimmune hemolysis, G6PD deficiency, and ANA for autoimmune diseases) and do not diagnose pernicious anemia.

Pernicious anemia is B12 deficiency caused by lack of intrinsic factor from autoimmune destruction of stomach parietal cells. The Schilling test was historically used to determine whether B12 malabsorption is intrinsic factor–dependent. In the first stage, radiolabeled B12 is given orally and the amount excreted in the urine is measured; in pernicious anemia this excretion is low because intrinsic factor is absent. The test is repeated in a second stage with intrinsic factor added; if the urinary excretion normalizes, it confirms that the malabsorption was due to intrinsic factor deficiency. So the Schilling test would yield a positive finding by showing abnormal B12 absorption that corrects with intrinsic factor, pointing to pernicious anemia. The other tests listed assess different conditions (Coombs for autoimmune hemolysis, G6PD deficiency, and ANA for autoimmune diseases) and do not diagnose pernicious anemia.