ARUP's Laboratory Test Directory

Xylose Absorption Test (Child) : 0020612

Mnemonic: XYLOSE P

Methodology: Spectrophotometry
Performed: Tue, Thu
Reported: 1-5 days
Specimen Required: Collect:  • Children are defined as less than 17 years old for purposes of this test.
• 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).
• Just prior to start of test, collect the first serum sample.  (Min: 0.5 mL serum)  Label this sample as "FASTING SERUM."
• Give children 0.5 g D-xylose per kilogram of body weight, up to 25 g; give xylose in water (5 mL of water per 0.5 g of xylose, up to 250 mL water). Encourage the patient to drink additional water following the xylose dose. The patient may have water as desired, but no other food or fluids. 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 one hour after giving the xylose dose.  (Min: 0.5 mL serum) Label this sample as "ONE-HOUR SERUM."
• After giving the xylose dose, collect all urine for the next five hours. Measure and record the volume, mix well and remove a 5 mL aliquot (Min: 3 mL) for transport. Label this sample as "FIVE-HOUR URINE." 
If unable to collect pediatric urine specimens, testing will be completed with a disclaimer, provided both serum specimens are received.

Record the xylose dose given and the total volume of the five-hour urine on the test request form. 
Send and label the fasting and one-hour serum samples. 
Record the total volume and xylose dose given on the urine aliquot tube. 
Failure to include required information will result in delayed turnaround time.

Pediatric Collection/Transport:  (FASTING SERUM): "ONE-HOUR SERUM" and "FIVE-HOUR URINE" aliquot at 2-8°C.  (Min: 0.1 mL per timed sample)  Please label samples completely.  Record five-hour urine volume on urine aliquot tube and dose of xylose given on test request form.

Remarks:  Serum is the preferred blood sample. Allow serum to clot completely at room temperature.  Separate serum from cells ASAP. The "fasting" serum sample does not have a reference interval since it is used as a blank for the one-hour serum sample.

Unacceptable Conditions:  Grossly hemolyzed serum and nonfasting samples. Whole blood or unspun clot tubes.

Stability:  Ambient: 4 hours; Refrigerated: 1 week; Frozen: 1 month
Reference Interval:
 
Components Reference Interval
Serum, fasting specimen
(There are no reference intervals for the fasting specimen; it is used as a patient "blank" when testing the one-hour specimen.) 		0-16 years: None
Serum xylose, one hour following ingestion 0-5 months: 15-58 mg/dL
6 months-16 years: 20-58 mg/dL
Fraction of xylose dose excreted in five hours in urine 0-16 years: 16-40% of dose
Amount of xylose excreted in five hours in urine 0-16 years: depends on dose given

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.
CPT Code(s): 84620
 
 

 

 

 
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