Galactose-1-phosphate uridyltransferase is a blood test that measures the level of a substance called GALT, which helps break down milk sugars in your body. Low levels of this substance cause a condition called galactosemia.
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. This is called a venipuncture.
How the test will feel
When the needle is inserted to draw blood, some infants feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
In normal diets, most galactose comes from the breakdown (metabolism) of lactose, which is found in milk and dairy products. About 1 out of 65,000 newborns lack a substance (enzyme) called GALT. Without this substance, the body can't break down galactose, and the substance builds up in the blood. Continued use of milk products can lead to:
The normal range is 18.5 - 28.5 U/g Hb (units per gram of hemoglobin).
Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
The examples above show the common measurements for results for these tests. Some laboratories use different measurements or may test different samples.
What abnormal results mean
An abnormal result suggests galactosemia. Further tests must be done to confirm the diagnosis.
If your child has galactosemia, a genetics specialist should be consulted promptly. The child should immediately be placed on a no-milk diet. This means no breast milk and no animal milk. Soy milk and infant soy formulas are generally used as substitutes.
What the risks are
Veins and arteries vary in size from one patient to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.
Other risks associated with having blood drawn are slight but may include:
Fainting or feeling light-headed
Hematoma (blood accumulating under the skin)
Infection (a slight risk any time the skin is broken)
Early diagnosis is important, because the disease can be treated by removing dairy products from the diet.
Every state requires newborn screening tests to check for this disorder. These screening tests are very sensitive so they do not miss many infants with galactosemia. But, false-positives can occur. If your child has an abnormal screening result, follow-up tests must be done to confirm the result.
Kishnani PS, Chen Y. Defects in Metabolism of Carbohydrates. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF, eds. Nelson Textbookof Pediatrics. 19th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 81.
Chad Haldeman-Englert, MD, FACMG, Wake Forest School of Medicine, Department of Pediatrics, Section on Medical Genetics, Winston-Salem, NC. Review provided by VeriMed Healthcare Network. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, and Stephanie Slon.