Anemias USMLE Step 1 Practice Question
A 73-year-old man presents to clinic with a 3-month history of progressive dyspnea on exertion, fatigue, and bilateral lower extremity paresthesias. He has a past medical history of hypothyroidism managed with levothyroxine. Vital signs are stable. Laboratory studies show hemoglobin 8.9 g/dL, MCV 104 fL, and serum B12 145 pg/mL (normal >200 pg/mL). Serum methylmalonic acid is elevated at 2.8 μmol/L (normal <0.4). Parietal cell antibodies and intrinsic factor antibodies are positive. Upper endoscopy reveals chronic atrophic gastritis with intestinal metaplasia. Which of the following findings would most reliably confirm the diagnosis of pernicious anemia?
Answer choices
- AElevated serum homocysteine level
- BAbnormal Schilling test that corrects with intrinsic factorCorrect answer
- CLow serum folate level
- DHypersegmented neutrophils on peripheral blood smear
- EElevated serum gastrin level with achlorhydria
- FLow serum transcobalamin II level
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