Galactosemia Test
Test Overview Galactose is a sugar that is part of the
lactose found in milk and milk products. A galactosemia test is a blood or
urine test that checks for
enzymes that are needed to change galactose into
glucose, a sugar that your body uses for energy. A person with
galactosemia doesn't have one of these enzymes, so
high levels of galactose build up in the blood or urine. When
galactose builds up in a baby's blood, it can cause liver damage, problems with eating, and
intellectual disabilities. The damage caused by galactosemia can begin within
weeks after the baby has started drinking breast milk or formula. Babies with
galactosemia need foods low in galactose in order to gain weight and to prevent
brain damage, liver problems, infection, and
cataracts. Galactosemia is a rare
disease that is passed from parents to children (inherited genetic disorder). A galactosemia test is usually done to determine whether a
newborn has the disease. In a family with a member who has galactosemia, a
genetic test can be done on adults to find out whether they have an increased
chance of having a child with the disease. Why It Is DoneA galactosemia test is done to: - Find out whether a newborn has the enzymes
needed to change galactose into glucose.
- See whether diet changes are working for a child who has galactosemia.
How To PrepareYou do not need to do anything before you have this test. Talk to your doctor about any concerns
you have about the need for the test, its risks, how it will be done, or what
the results will mean. To help you understand the importance of this test, fill
out the
medical test information form(What is a PDF document?). How It Is DoneTests for galactosemia are done on a
blood or urine sample. Blood sample from a heel stickIf galactosemia
testing is done on a baby, a heel stick will be done instead of a blood draw
from a vein. For a heel stick blood sample, several drops of blood are
collected from the heel of the baby. The skin of the heel is cleaned with
alcohol and then punctured with a sterile lancet. Several drops of blood are
collected inside circles on a specially prepared piece of paper. When enough
blood has been collected, a gauze pad or cotton ball is placed over the
puncture site. Pressure is maintained on the puncture site briefly to stop the
bleeding, and then a small bandage is usually applied. A blood sample is
usually collected within 2 to 3 days after birth. If the test
shows that the baby has galactosemia, the results will be confirmed on a blood
sample taken from a vein. Blood sample from a vein The health professional
drawing your child's blood will: - Wrap an elastic band around your child's
upper arm to stop the flow of blood. This makes the veins below the band larger
so it is easier to put a needle into the vein.
- Clean the needle
site with alcohol.
- Put the needle into the vein. More than one
needle stick may be needed.
- Attach a tube to the needle to fill it
with blood.
- Remove the band from your child's arm when enough blood
is collected.
- Apply a gauze pad or cotton ball over the needle site
as the needle is removed.
- Apply pressure to the site and then a
bandage.
Urine sampleTo test for galactose in a urine
sample from a baby, a health professional will tape a plastic collection bag to
the baby's genital area. After the baby urinates, the collection bag is
removed. A blood test for galactose is more accurate than a urine test. How It FeelsBlood sample from a heel stickA quick sting or a
pinch is usually felt when the lancet punctures the skin. Your baby may have a
little discomfort with the skin puncture, but this does not last long. Blood sample from a veinYour baby may feel
nothing at all from the needle puncture, or he or she may feel a brief sting or
pinch as the needle goes through the skin. Some people feel a stinging pain
while the needle is in the vein. But many people do not feel any pain (or have
only minor discomfort) after the needle is positioned in the vein. The amount of
pain you feel depends on the skill of the health professional drawing the
blood, the condition of your baby's veins, and your baby's sensitivity to
pain. Urine sampleA baby will usually feel no
discomfort from the use of a urine collection bag. But removing the tape that
attaches the bag to the skin may cause temporary discomfort. RisksHeel stick blood sampleThere is very little risk
of a problem from a heel stick. Your baby may get a small bruise at the puncture
site. Blood sample from a veinThere is very little chance of a problem from having blood drawn from a vein. - Your baby may get a small bruise at the
puncture site. You can lower the chance of bruising by keeping pressure on the
site for several minutes.
- In rare
cases, the vein may become swollen after the blood sample is taken. This
problem is called phlebitis. You can use a warm compress
several times a day to treat this.
Urine sampleThere are no risks linked with a
urine test for galactosemia. Removing the tape that holds the bag in place may
cause mild skin irritation. ResultsA galactosemia test is a blood or urine
test that checks for the
enzymes that are needed to change galactose into
glucose, a sugar that your body uses for energy. Galactose tests (blood or urine)| Normal: | Negative (galactosemia is not
present) |
|---|
| Abnormal: | Positive (galactosemia is
present) |
|---|
The normal values listed here-called a reference range-are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab. Galactose-1-phosphate uridyltransferase (GPT) test (blood)| Normal:footnote 1 | 18.5-28.5
units per gram (U/g) of hemoglobin (1.19-1.84
milliunits per mole of hemoglobin [mU/mol Hb]): The person does not have
galactosemia. |
|---|
| Abnormal:footnote 2 | Less than 5 U/g of hemoglobin (less than
0.32 mU/mol Hb): The person has galactosemia. |
|---|
5-18.5 U/g of hemoglobin (0.32-1.18 mU/mol
Hb): The person may be a
carrier of galactosemia and able to pass the disease
on to his or her child. | Galactokinase enzyme test (blood)footnote 1| Normal: | Adults: 12-40 milliunits per gram of
hemoglobin (mU/g Hb) (200-667 pkat/g Hb) |
|---|
Children 2-18 years: 11-54
mU/g Hb (183-900 pkat/g Hb) | Children 0-2 years: 11-150 mU/ g Hb
(183-2500 pkat/g Hb) | | Abnormal: | Lower-than-normal values, depending on
age |
|---|
A newborn screening test that shows the baby has an increased risk of
galactosemia will be confirmed by other tests. Many conditions can change galactose levels. Your doctor will discuss any
significant abnormal results with you in relation to your baby's symptoms and
past health. What Affects the TestReasons you may not be able to
have the test or why the results may not be helpful include: - A blood transfusion.
- Improper
placement of a urine collection bag on a baby.
What To Think About- Early detection and treatment of galactosemia
is very important, because the disease can cause brain damage, liver failure,
and
cataracts if it is not treated. Within 24 hours of
drinking breast milk or formula, galactose blood levels in a baby with
galactosemia start to rise. A galactosemia test 2 to 3 days after birth will
show whether your baby has galactosemia. Almost all states in the United
States have laws that require galactosemia testing of newborns within a few
days of birth.
- If your baby's test is positive, the test will be
repeated to confirm the diagnosis.
- If test results confirm that
your baby has galactosemia, ask to speak to a
dietitian. A substitute for breast milk or milk-based
formula, such as formula made from soy, will prevent damage caused
by galactosemia. It will never be safe to give milk or milk products to a child
who has galactosemia.
- If you or your partner knows that you are a carrier of
galactosemia or if you have family members with galactosemia, you may want to
have
genetic counseling to learn about the disease and the
likelihood of passing it to your children. To learn more, see the
topic
Genetic Test.
ReferencesCitations- Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health.
- Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
Other Works Consulted- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
CreditsByHealthwise Staff
Primary Medical ReviewerKathleen Romito, MD - Family Medicine
Martin J. Gabica, MD - Family Medicine
Specialist Medical ReviewerSiobhan M. Dolan, MD, MPH - Reproductive Genetics Current as ofOctober 13, 2016 Current as of:
October 13, 2016 Fischbach F, Dunning MB III (2015). A Manual of Laboratory and Diagnostic Tests, 9th ed. Philadelphia: Wolters Kluwer Health. Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders. Last modified on: 8 September 2017
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