A 30-year-old woman presents with a 6-month history of chronic diarrhea, bloating, and unintentional weight loss. She also reports fatigue and has been found to have iron-deficiency anemia refractory to oral iron supplementation. Laboratory tests reveal positive anti-tissue transglutaminase (tTG) IgA antibodies and elevated total IgA. What is the most appropriate next step to confirm the diagnosis?
✓ Correct Answer: Option B
While serology (positive anti-tTG IgA) is highly suggestive of celiac disease in a symptomatic patient, definitive diagnosis requires characteristic histological changes on duodenal biopsies obtained via upper endoscopy. Patients must continue a gluten-containing diet until biopsy.