This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Medicine
[{'content': 'Positive D-xylose test indicates all of the following except: March 2011 \nSelect and explain. \nA. Pancreatic insufficiency, B. Small intestinal mucosal disease, C. Impaired carbohydrate absorption in small intestine, D. Malabsorption', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A: Pancreatic insufficiency The urinary D-xylose test for carbohydrate absorption provides an assessment of proximal small-intestinal mucosal function Xylose: It is used to test for malabsorption by administration in water to the patient after fasting. If xylose is detected in blood and/or urine within the next few hours, it has been absorbed by the intestines. Reduction of xylose by catalytic hydrogenation produces the non-cariogenic sugar substitute xylitol. D-xylose absorption test for mucosal disease or bacterial over growth, is normal in pancreatic insufficiency.', 'role': 'assistant'}]