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Test Name:
Xylose Absorption Test (Adult - 5g dose)
- SBMF No:
44786 - Performance Lab Name:
ARUP Laboratories - Test Mnemonic:
XYL-5G - ABN:
Not required - CPT Code:
84620 - Ref Lab Test No:
0020615 - Also Known As:
D-xylose Absorption Test - Also See:
44787 Xylose Absorption Test (Adult - 25 g dose) - Spec Type:
Serum, Fasting AND
Serum, 2-hour AND
Urine, 5-hour - Spec Container:
Gold top (SST) or red top (serum) tubes, AND
Plastic container with tightly fitting lid (no preservative) - Pref Vol:
Serum: 1.0 mL (each)
Urine: 5.0 mL - Min Vol:
Serum: 0.5 mL (each)
Urine 3.0 mL - Fasting:
Yes - Patient Prep:
The patient should fast for eight hours (minimum four hours) prior to starting test.
Just prior to start of test, the patient should empty his or her bladder (DO NOT collect this urine). - Spec Collect:
Just prior to start of test, collect the first serum sample. Label this specimen as "FASTING SERUM."
Give adults 5 g D-xylose in 250 mL water. Encourage the patient to drink an additional 250 mL water following the xylose dose. The patient may have water as desired, but no other food or fluids. Smoking should be prohibited. The patient should rest in a chair or on a bed until completion of test. Mild diarrhea is common following xylose ingestion.
Collect the second serum sample two hours after giving the xylose dose. Label this specimen as "TWO-HOUR SERUM."
After giving the xylose dose, collect all urine for the next five hours. Label this specimen as "FIVE-HOUR URINE." - Spec Process:
- Serum:
- – Allow to clot completely at room temperature
– Promptly centrifuge 15 minutes
– Transfer serum to separate plastic tube - Urine:
- – Measure and record the volume
– Mix well
– Remove a 5 mL aliquot for transport Record the xylose dose given and the total volume of the five-hour urine on the test request form.
Clearly label samples as "FASTING SERUM", "TWO-HOUR SERUM", and "FIVE-HOUR URINE"
Record the total volume and the xylose dose given on the urine aliquot tube
Failure to include required information will result in delay of turnaround time
- Spec Store Transport:
Refrigerated - Spec Stability:
4 hours room temperature (20-30°C)
1 week refrigerated (2-8°C)
1 month frozen (-20°C) – Do not use frost-free units that undergo repeated freeze/thaw cycles - Spec Reject:
Grossly hemolyzed sample
Non-fasting sample
Whole blood or unspun clot tubes - Methodology:
Spectrophotometry - Clinical Significance:
Refer to:
- Reference Range:
- Serum, fasting specimen
- 17 years and older: None
(There are no reference intervals for the fasting serum specimen; it is used as a patient "blank" when testing the two-hour specimen.) - 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
- Note:
- 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.
- Additional Test Info:
The xylose absorption test can be performed using a 25 g dose of xylose, or a 5 g dose. The 5 g dose is generally preferred in patients who do not tolerate the 25 g dose. - Day Run:
Tue, Thu - Time Reported:
2-6 days - Test Type:
CHEMISTRY
