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Abdominal aortic aneurysm — USMLE Step 2 CK MCQ

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HardInternal MedicineAbdominal aortic aneurysmUSMLE Step 2 CK

A 39-year-old woman has 8 months of chronic diarrhea, iron-deficiency anemia, abdominal bloating, and unintentional weight loss. Her tissue transglutaminase IgA is negative, but total serum IgA is undetectable. She has continued eating a gluten-containing diet, has no recent travel, and stool pathogen testing is negative. Which test is most appropriate next?

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Correct answer: D — Measure tissue transglutaminase IgG or deamidated gliadin peptide IgG

The best answer is “Measure tissue transglutaminase IgG or deamidated gliadin peptide IgG”. Selective IgA deficiency can make tTG-IgA falsely negative despite active celiac disease. Because she is consuming gluten and has high clinical suspicion, an IgG-based celiac assay such as tTG-IgG or deamidated gliadin peptide IgG is the appropriate next test, followed by endoscopic biopsy when indicated. HLA testing can help exclude disease when negative but does not confirm it, and starting a gluten-free diet before evaluation reduces diagnostic sensitivity.

Reference: NIDDK: celiac disease tests for health professionals. https://www.niddk.nih.gov/health-information/professionals/clinical-tools-patient-management/digestive-diseases/celiac-disease-health-care-professionals