Galactosemia Test
Reviewed
Also called: galactosemia newborn screening test, GALT test
A galactosemia test is a blood test used in newborns to screen for a rare genetic metabolic disorder that prevents the body from breaking down galactose, a sugar found in milk, dairy, and some fruits and vegetables. The test is part of routine newborn screening in the United States. A positive screen requires follow-up testing to confirm the diagnosis and determine the specific enzyme deficiency. Early diagnosis and dietary management can prevent serious health problems such as liver disease, kidney failure, brain damage, or death. The test involves a heel prick and carries minimal physical risk.
Specimen: Blood (heel stick)
Why this test may be ordered
- Newborn screening is required in the United States to check for galactosemia shortly after birth.
- Older infants adopted from other countries may be tested if they show symptoms such as vomiting, poor weight gain, refusal to eat, irritability, or jaundice.
Preparation and collection
No special preparation is needed.
A health care provider will clean your baby's heel with alcohol, then poke the heel with a small needle to collect a few drops of blood.
The heel prick may cause a brief pinch and a small bruise that resolves quickly. There are no known serious risks from the blood collection procedure.
Understanding results
Results are reported as screen-negative or screen-positive. This test is a screening tool; it does not provide a definitive diagnosis. Interpretation should be done by your healthcare professional, who will consider your baby's symptoms and may order confirmatory tests.
- Screen-negative: Lower likelihood of galactosemia. The baby's body appears to have normal ability to break down galactose. Limitation: Screen-negative results do not completely rule out galactosemia; if symptoms develop, further evaluation may be needed. Next step: No additional tests are typically required. Continue routine newborn care and monitor for any signs of galactosemia.
- Screen-positive: Higher likelihood of galactosemia, meaning the baby may have a deficiency in one of the enzymes needed to break down galactose (GALT, GALK, or GALE). Limitation: Screen-positive results may occur due to false positives; confirmatory testing is essential to avoid unnecessary dietary changes. Next step: Your baby will need further diagnostic testing (blood, urine, genetic tests) to confirm or rule out galactosemia and identify the specific enzyme deficiency. Prompt follow-up is important because early treatment can prevent serious complications.
- The heel prick may cause a brief pinch and a small bruise that resolves quickly.
- As a screening test, there is a risk of false-positive (suggesting a problem when none exists) and false-negative (missing a problem) results. Further testing is needed to confirm any positive screen due to the possibility of laboratory error or other factors.
What to do next
If the result is screen-negative, no immediate follow-up is needed, but report any symptoms (vomiting, poor weight gain, refusal to eat, irritability, jaundice) to your healthcare provider. If the result is screen-positive, your baby will need additional blood tests, urine tests, and genetic tests to confirm the diagnosis and determine the specific enzyme deficiency (GALT, GALK, or GALE). Early diagnosis and dietary management (e.g., soy formula, lactose-free formula, and lifelong avoidance of milk/dairy for classic galactosemia) can prevent serious health problems. There is no cure, and children with classic galactosemia require a special diet and calcium supplements. Those with GALK or GALE deficiencies may be able to include limited dairy. Discuss a safe diet and follow-up plan with your healthcare provider.
- What is the purpose of this test?
- How is the test performed?
- What do the results mean?
- What are the next steps if the result is screen-positive?
- Are there any risks or limitations?