D-xylose absorption
Alternative names:
xylose tolerance test
How the test is performed:
An initial blood and urine sample are taken.
Child or adult:
Urine collection:
Collect a "clean-catch" ("midstream") urine sample. To obtain a clean-catch sample, men or boys should wipe clean the head of the penis. Women or girls need to wash the area between the lips of the vagina with soapy water and rinse well. As you start to urinate, allow a small amount to fall into the toilet bowl (this clears the urethra of contaminants). Then, in a clean container, catch about 1 to 2 ounces of urine and remove the container from the urine stream. Give the container to the health care provider or assistant.
Blood collection:
Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic, and a tourniquet (an elastic band) or blood pressure cuff is placed around the upper arm to apply pressure and restrict blood flow through the vein. This causes veins below the tourniquet to distend (fill with blood). A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. During the procedure, the tourniquet is removed to restore circulation. Once the blood has been collected, the needle is removed, and the puncture site is covered to stop any bleeding.
Infant:
Urine collection:
Thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on your infant. For males, the entire penis can be placed in the bag and the adhesive attached to the skin. For females, the bag is placed over the labia. Place a diaper over the infant (bag and all). Check your baby frequently and remove the bag after the infant has urinated into it. For active infants, this procedure may take a couple of attempts--lively infants can displace the bag, causing an inability to obtain the specimen. The urine is drained into a container for transport back to the health care provider.
Blood collection:
The area is cleansed with antiseptic and punctured with a sharp needle or a lancet. The blood may be collected in a pipette (small glass tube), on a slide, onto a test strip, or into a small container. Cotton or a bandage may be applied to the puncture site if there is any continued bleeding.
You are given 25 grams of D-xylose in 8 oz. of water. Blood is collected after 2 hours, and sometimes again after 5 hours. Urine is re-tested after 8 hours. Urine excretion over a 5 hour period is also determined (all of the urine is collected for 5 hours).
How to prepare for the test:
Fast for 8 to 12 hours before the test. Consult the health care provider about the need to withhold drugs that can affect test results (see "special considerations").
If the collection is being taken from an infant, a couple of extra collection bags may be necessary.
Infants and children:
The physical and psychological preparation you can provide for this or any test or procedure depends on your child's age, interests, previous experience, and level of trust. For specific information regarding how you can prepare your child, see the following topics as they correspond to your child's age:
How the test will feel:
When the needle is inserted to collect the blood, a stinging sensation or prick will be felt. After the blood has been drawn, the puncture site may throb for a few minutes, and may feel bruised for a day or two.
Why the test is performed:
This test may be performed to help evaluate cases of:
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