Galactose-1-phosphate uridyltransferase

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Galactose-1-phosphate uridyltransferase

Definition:

Galactose-1-phosphate uridyltransferase is a blood test that measures the level of GALT, an enzyme involved in breakdown of milk sugars (lactose/galactose).

Alternative Names:

Galactosemia screen; GALT; Gal-1-PUT

How the test is performed:

Blood is drawn from a vein, usually from the inside of the elbow or the back of the hand. The puncture site is cleaned with antiseptic. An elastic band is placed around the upper arm to apply pressure and cause the vein to swell 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 band 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.

In infants or young children:

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. A bandage may be applied to the puncture site if there is any bleeding.

How to prepare for the test:

No special preparation is necessary.

How the test will feel:

When the skin is pricked with the needle, the amount of discomfort varies. Some people experience moderate pain while others feel only a prick or stinging sensation. Afterward, the site may be bruised for a few days.

Why the test is performed:

This is a screening test for galactosemia.

In normal diets, the major source of galactose is in the metabolism of lactose. The major source of dietary lactose is milk and dairy products. In most people, galactose is converted to glucose by a series of chemical reactions. Each chemical reaction is catalyzed by an enzyme.

About 1 out of 65,000 newborns has a deficiency of the GALT enzyme (deficiencies of the other enzymes are much less common). As a consequence, galactose accumulates in the blood (galactosemia) and tissues because it cannot be metabolized.

Because milk is an important part of the diet of most newborns, these infants develop fluid imbalance and failure to thrive. Continued use of galactose can also result in cataracts, jaundice, liver enlargement, cirrhosis, and mental retardation.

Review Date: 4/20/2005
Reviewed By: Neal Sondheimer, M.D., PhD., Division of Genetics and Metabolism, Children's Hospital of Philadelphia, Philadelphia, PA. Review provided by VeriMed Healthcare Network.

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