|Serum, fasting specimen|
(There are no reference intervals for the fasting serum specimen; it is used as a patient "blank" when testing the two-hour specimen.)
|17 years and older: None
|Serum xylose, two hours following ingestion
||17 years and older: 5-17 mg/dL
|Fraction of xylose dose excreted in five hours in urine
||17 years and older: 20-40% of dose
|Amount of xylose dose excreted in five hours in urine
||17 years and older: 1.2-2.0 g/5 hours
||The xylose absorption test evaluates carbohydrate absorption by the mucosa of the proximal small intestine. In patients with renal deficiency, rely on the serum test only. In functionally anephric patients, the test is unreliable. A number of drugs can interfere with test results, including: aspirin, atropine, colchicine, digitalis, indomethacin, MAO inhibitors, nalidixic acid, neomycin, opium alkaloids, and phenelzine. Nonfasting serum samples are often compromised by significant analytic interferences.
The xylose absorption test can be performed using a 25 g dose of xylose. Refer to Xylose Absortion Test (Adult-25 g dose) (0020609) or a 5 g dose, refer to Xylose Absortion Test (Adult -5 g) (0020615) as described here. The 5 g dose is generally preferred in patients who do not tolerate the 25 g dose.
||D-xylose (Xylose Absorption Test (Adult - 5g dose))