A 58-year-old woman has a gastric ulcer, achlorhydria, and vibration sense loss in the lower extremities. She has a megaloblastic anemia. What test would help support a diagnosis of pernicious anemia?
Response to injection of radioactive B12 Endoscopic retrograde cholangiopancreatography (ERCP) Prothrombin time (PT) Radiolabeled B12 given orally