XYLOSE ABSORPTION TEST

LAB453

Collect

Fasting serum, five-hour urine, and two-hour serum according to the following instructions.

Patient Preparation

Patient should fast for 8 hours (Min: 4 hours) prior to administration of xylose.

Specimen Preparation

1. Just prior xylose administration, patient should empty his or her bladder (DO NOT collect this urine).
2. Just prior to xylose administration, collect first serum specimen (Min: 0.5 mL). Allow serum to clot completely at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Label this specimen as "FASTING SERUM" and prepare for transport.
3. Give adults 25 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.
4. Immediately following 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) and prepare for transport. Label this specimen as "FIVE-HOUR URINE." Record the total volume and the xylose dose given on the urine aliquot tube.
5. Two hours after administration of xylose dose, collect the second serum specimen (Min: 0.5 mL). Allow serum to clot completely at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Label this specimen as "TWO-HOUR SERUM" and prepare for transport.
6. Record the xylose dose given and the total volume of the five-hour urine on the test request form.
Failure to include all required information will result in delay of turnaround time.

Unacceptable Conditions

Non-fasting specimens. Whole blood or unspun clot tubes. Grossly hemolyzed serum.

Storage/Transport Temperature

Refrigerated.

Stability (from collection to initiation)

Ambient: 4 hours; Refrigerated: 1 week; Frozen: 1 month

Remarks

The fasting serum specimen does not have a reference interval since it is used as a blank for the two-hour serum sample.
For children, refer to Xylose Absorption Test (Child) (ARUP test code 0020612).

Notes

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.

Performed

Tue, Thu

Methodology

Quantitative Spectrophotometry

Reported

1-5 days

Synonyms

  • D-xylose (Adult - 25 g dose)
  • LAB453

Ordering Recommendations

Nonstandard test for determining cause of malabsorption. Test evaluates carbohydrate absorption of the proximal small intestine. Refer to 5g dose testing for patients who do not tolerate the 25g dose.

Reference Interval

Components
Reference Interval
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 ingestion17 years and older: 32-58 mg/dL
Fraction of xylose dose excreted in five hours in urine17-64 years: 16-40% of dose
65 years and older: 14-40% of dose
Amount of xylose excreted in five hours in urine17-64 years: 4.0-10.0 g/5 hours
65 years and older: 3.5-10.0 g/5 hours

CPT Codes

84620
Collection

LAB453

Collect

Fasting serum, five-hour urine, and two-hour serum according to the following instructions.

Patient Preparation

Patient should fast for 8 hours (Min: 4 hours) prior to administration of xylose.

Specimen Preparation

1. Just prior xylose administration, patient should empty his or her bladder (DO NOT collect this urine).
2. Just prior to xylose administration, collect first serum specimen (Min: 0.5 mL). Allow serum to clot completely at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Label this specimen as "FASTING SERUM" and prepare for transport.
3. Give adults 25 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.
4. Immediately following 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) and prepare for transport. Label this specimen as "FIVE-HOUR URINE." Record the total volume and the xylose dose given on the urine aliquot tube.
5. Two hours after administration of xylose dose, collect the second serum specimen (Min: 0.5 mL). Allow serum to clot completely at room temperature. Separate serum from cells ASAP or within 2 hours of collection. Label this specimen as "TWO-HOUR SERUM" and prepare for transport.
6. Record the xylose dose given and the total volume of the five-hour urine on the test request form.
Failure to include all required information will result in delay of turnaround time.

Unacceptable Conditions

Non-fasting specimens. Whole blood or unspun clot tubes. Grossly hemolyzed serum.

Storage/Transport Temperature

Refrigerated.

Stability (from collection to initiation)

Ambient: 4 hours; Refrigerated: 1 week; Frozen: 1 month

Remarks

The fasting serum specimen does not have a reference interval since it is used as a blank for the two-hour serum sample.
For children, refer to Xylose Absorption Test (Child) (ARUP test code 0020612).

Notes

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.
Ordering

Performed

Tue, Thu

Methodology

Quantitative Spectrophotometry

Reported

1-5 days

Synonyms

  • D-xylose (Adult - 25 g dose)
  • LAB453

Ordering Recommendations

Nonstandard test for determining cause of malabsorption. Test evaluates carbohydrate absorption of the proximal small intestine. Refer to 5g dose testing for patients who do not tolerate the 25g dose.
Result Interpretation

Reference Interval

Components
Reference Interval
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 ingestion17 years and older: 32-58 mg/dL
Fraction of xylose dose excreted in five hours in urine17-64 years: 16-40% of dose
65 years and older: 14-40% of dose
Amount of xylose excreted in five hours in urine17-64 years: 4.0-10.0 g/5 hours
65 years and older: 3.5-10.0 g/5 hours

Administrative

CPT Codes

84620