Xylose Absorption Test (D-Xylose) &nbs= p;
Absorption of the pentose xylose from the gastrointe= stinal tract appears to be more dependent on proper function of the absorptive mec= hanism than other simple sugars. The recovery of xylose in the urine is a function= of the amount absorbed in the blood from the gastrointestinal tract, providing renal function is normal. Blood samples and urine may be analyzed at inter&= shy;vals to measure the amount of xylose absorbed. The standard xylose tolerance test includes three samples; 5 hour urine sample, fasting and two hour blood samples. However physicians may request only serum or only urine samples for analysis.
1. = Xylose is obtained through the Pharmacy. It should be requested in advance to allow time for preparation. The standard adult test requires a 25G dose, while 5G dose is used for young children.
2. = Obtain a urine collection container from the Laboratory for the 5 hour urine speci= men (if required). Catch basins are available if needed.
3. = The patient should fast overnight. Infants should fast for at least 4 hours.
While it is not necessary to schedule this test in a= dvance with the Laboratory, the lab should be notified of any outpatient test= ing so that the xylose dose can be obtained from the pharmacy.
The procedure is ordered as “Xylose Absorption Test”. Labels will generate on the patient care unit and will include= one for a “fasting” serum xylose, one for a post dose “2 hour” serum xylose, and one for the 5 hour urine xylose. The time of = dose should be noted on the large main label.
1. = Food and fluids are withheld for at least 8 hrs.
2. = The patient’s bladder should be emptied. This urine is discarded.
3. = Just prior to the start of the test, a fasting serum sample is drawn. Send to the lab ASAP so that the serum can be separated from the cells. Avoid hemolysis= .
4. = Give the patient 25 G of D-Xylose orally, dissolved in 250 mL of tap water. Encourage the patient to drink an additional 250 mL of water following the dose. (The patient may have water as desired, but no other food or fluids. Smoking is also prohibited.) The patient should rest in a chair or on a bed until the test is completed. Mild diarrhea is common following the xylose ingestion. The D-Xylose ingestion time must be noted on the large preprinted computer label. If any change in oral xylose administration is made, the lab must be notified immediately.
5. = Collect and pool all urine for the next 5 hours. When complete, send the specimen to the lab.
6. = 2 hours following the xylose ingestion a second serum specimen will be drawn = and labeled with the “2 hour” serum xylose label. Send to the lab A= SAP so that it can be spun down and separated.
1. = All patients except infants must fast overnight; infants must fast for at least= 4 hours.
2. = The patient’s bladder should be emptied. This urine is discarded.
3. = Just prior to the start of the test, a fasting serum sample is drawn. Send to the lab ASAP so that the serum can be separated from the cells. Avoid hemolysis= .
4. = The patient is given 0.5 G D-Xylose/ lb body weight in an aqueous solution of 5= -10 G/100 mL. (The patient may have water as desired, but no other food or flui= ds.) The patient should rest in a chair or on a bed until the test is completed. Mild diarrhea is common following the xylose ingestion. The D-Xylose ingest= ion time must be noted on the large preprinted computer label.
5. = Collect and pool all urine for the next 5 hours. When complete send the specimen to= the lab.
6. = 1 hour following the xylose ingestion a second serum specimen will be drawn a= nd sent to the lab ASAP to be spun down and separated.
A low urine xylose concentration is indicative of gastrointestinal tract malabsorption or renal insufficiency. In the normal adult, blood values should rise over 25 mG xylos= e per 100 mL after a 25G dose.
Xylose is charged to the patient through the pharmac= y.
Document Control
Facility: Central Maine Med=
ical
Center, 300 Main Street, Lewiston, Maine&n=
bsp;
04240
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