FXAB - Specimen: Xylose Absorption Test (Adult 25g dose)

Test Catalog

Test Name

Test ID: FXAB    
Xylose Absorption Test (Adult 25g dose)

Specimen Type Describes the specimen type needed for testing

Timed Serum

Specimen Required Defines the optimal specimen. This field describes the type of specimen required to perform the test and the preferred volume to complete testing. The volume allows automated processing, fastest throughput and, when indicated, repeat or reflex testing.

SUBMIT ALL OF THE FOLLOWING (Read ALL collection information prior to start of test and collection of specimens.)


Serum-Required: Fasting serum and Two-hour specimen Collect blood in plain, red-top tube(s), allow to clot completely at room temperature. Separate from cells ASAP and label tube with "Fasting serum" or "Two-hour serum" as appropriate. Ship specimens refrigerate.



Collect all urine for five hours. Measure and record the volume, mix well and remove a 5 mL aliquot, label sample "Five-hour urine". Ship specimen refrigerate.


REQUIRED COLLECTION INSTRUCTIONS - Read ALL collection information prior to start of test.


* 25 g Xylose dose must be obtained from a pharmacy.


* Patient should fast for eight hours prior to start of test.


* Patient should empty bladder prior to start of test. (do not collect)


* Prior to xylose administration, collect fasting serum sample, label tube

  Clearly "Fasting Serum"


* Give adults 25 g D-xylose in 250 mL water. Encourage patient to drink an additional 250 mL water following 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 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 tube clearly "Two-hour Serum".


* Immediately following xylose dose, COLLECT ALL URINE FOR THE NEXT FIVE HOURS.  Measure and record the volume, mix well and remove a 5 mL aliquot. Label sample "Five-hour Urine", record total volume and the xylose dose given.

Specimen Minimum Volume Defines the amount of specimen required to perform an assay once, including instrument and container dead space. Submitting the minimum specimen volume makes it impossible to repeat the test or perform confirmatory or perform reflex testing. In some situations, a minimum specimen volume may result in a QNS (quantity not sufficient) result, requiring a second specimen to be collected.

Serum: 0.5 mL Urine: 3 mL

Reject Due To Identifies specimen types and conditions that may cause the specimen to be rejected


Mild OK; Gross reject


Warm reject; Cold OK








Specimen Stability Information Provides a description of the temperatures required to transport a specimen to the laboratory. Alternate acceptable temperature(s) are also included.

Specimen TypeTemperatureTime
SerumRefrigerated (preferred)7 days
 Frozen 30 days
 Ambient 4 hours
Timed SerumRefrigerated (preferred)7 days
 Frozen 30 days
 Ambient 4 hours
UrineRefrigerated (preferred)7 days
 Frozen 30 days
 Ambient 4 hours