|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: 32-58 mg/dL
|Fraction of xylose dose excreted in five hours in urine
||17-64 years: 16-40% of dose|
65 years and older: 14-40% of dose
|Amount of xylose excreted in five hours in urine
||17-64 years: 4.0-10.0 g/5 hours|
65 years and older: 3.5-10.0 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.
For those patients who do not tolerate the 25 g xylose dose, a 5 g dose can be used, refer to Xylose Absorption Test (Adult - 5 g dose) (0020615). This change in dose must be noted on the test request form.
||D-xylose (Xylose Absorption Test (Adult - 25g dose))