Which test is used to distinguish maldigestion from malabsorption?

The D-xylose test is used to assess the absorption capability of the intestines and helps to distinguish maldigestion from malabsorption. In a patient with malabsorption, the body has difficulty taking in nutrients properly due to mucosal damage or dysfunction, even when digestive enzymes are functioning normally. D-xylose, a simple sugar, does not require any digestive enzymes for absorption. If the D-xylose test shows low levels in the urine or serum, it typically indicates a problem with absorption in the intestinal mucosa itself, confirming malabsorption.

In contrast, other tests like the stool fat test primarily assess maldigestion by measuring fat that remains unabsorbed in the stool, which occurs due to inadequate breakdown of fats, often due to enzyme deficiencies. The lactose tolerance test evaluates lactose digestion specifically, revealing issues pertaining to lactose intolerance rather than overall malabsorption. The serum albumin test assesses protein levels and can reflect general nutritional status but does not differentiate between maldigestion and malabsorption on its own. Thus, the D-xylose test is specifically geared toward identifying absorption issues distinct from digestion problems.