A 55-year-old woman presents to her PCP’s office complaining of generalized abdominal pain and bloating that has been bothering her for the past year. She reports her symptoms are worse especially after food intake. She also complains of weakness, fatigue, and feeling sad on most days. Otherwise, she denies chest pain, dyspnea, fever and chills. She lives with her husband of 30 years and denies every using alcohol, tobacco, or recreational drug use. She reports a history of c-section for her only pregnancy. Her family history is significant for Grave’s disease. Her routine labs are as follows:

• WBC 4,500
• Hemoglobin 7.9
• MCV 119
• Platelets 312,000
• Serum iron 109
• Serum B12 81 (low)
• Serum folate 13

What is the best next step in diagnosing her condition?

• A) Schilling test
• B) EGD with biopsy
• C) Order autoantibodies against intrinsic factor
• D) Bone marrow biopsy
• E) Stool antigen test for H pylori