Q2. Correct answer: D. Glucose hydrogen breath test.
The etiology of small intestinal bacterial overgrowth (SIBO) is complex but may include an issue with altered antibacterial defense mechanisms, such as achlorhydria from atrophic gastritis. SIBO can be diagnosed by a glucose hydrogen breath test, and therefore, it is the best next step in the management of this patient's symptoms given the history of atrophic gastritis. Chromogranin A testing and video capsule endoscopy are used in the diagnostic evaluation of suspected carcinoid syndrome and inflammatory bowel disease, respectively, and may be indicated in the subsequent evaluation of this patient's symptoms. In addition, both of these diagnoses are unlikely to cause intermittent diarrhea. Eluxadoline is an agent that combines a mu-opioid receptor agonist and a delta-opioid receptor antagonist and is indicated for the treatment of irritable bowel syndrome - diarrhea predominant (IBS-D). The diagnosis of IBS requires the presence of abdominal pain and is unlikely in an elderly patient with new onset of symptoms; therefore, this is not the diagnosis in this patient's case.
Jan Bures et al. World J Gastroenterol. 2010 Jun 28;16(24):2978-90.