Which is the following the test of choice for assessment of mucosal function of GIT?

D-Xylose is a carbohydrate which is normally absorbed from the small intestine. Measuring D-xylose level in the serum or its excretion in urine after ingestion, is used for the evaluation of carbohydrate absorption ability of the proximal small intestinal mucosa. Ref: Pocket Guide to Diagnostic Tests By Diana Nicoll, 5th Edition