Specimen

Serum and Urine

Collection Medium:

Minimum:

One "FASTING SERUM," one "TWO-HOUR SERUM," and one "FIVE-HOUR URINE"

Rejection Criteria:

Hemolyzed specimens.

Delivery Instructions:

Submit specimen to laboratory as soon as possible after
collection period is completed.

Specimen
Instructions:

Indicate dose and time of sampling on requisition.

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 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. 
(Min: 0.5 mL serum) Label this sample as "TWO-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."

Transport entire urine collection and blood specimens to Specimen 
Control (6240 RCP).

Analytic Time:

1 week

Reference Range:

Components                               Reference Interval

Serum, fasting specimen                  17 years(+): 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        17 years(+): 32-58 mg/dL
Ingestion

Fraction of xylose dose excreted in      17-64 years: 16-40% of dose
five hours in urine                      65 years(+): 14-40% of dose

Amount of xylose excreted in five        17-64 years: 4.0-10.0 g/5 hrs
hours in urine                           65 years(+): 3.5-10.0 g/5 hrs

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.

Comments:

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 
two-hour serum samples.  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.

Methodology:

Spectrophotometric

CPT Code:

84620

See Additional Information:
Fasting Specimen Requirements
Urine Tests Requiring no Preservatives