When the PKU test is done within 24 hours
of birth, there is a small chance that the test result will not be accurate (false-negative or false-positive). Your baby may need to be tested
again. There is less chance of a false result if the test is
done between 24 and 72 hours after birth.
If your baby has PKU, he or she will need regular blood tests to check phenylalanine levels. These tests may occur as often as once a week in your baby's first year and then once or twice a month throughout childhood.
Blood tests for
phenylalanine may be done if you have PKU and plan to
become pregnant. If you eat too much protein, you will have high levels of
phenylalanine in your blood. If you become pregnant, the high levels of
phenylalanine could cause your baby (fetus) to have
intellectual disability, even if your baby does not have PKU.
for phenylalanine levels in urine may be done if your baby is now over 6 weeks
of age and did not have a PKU blood test 2 to 3 days after birth. A PKU heel
stick can be done up to 6 weeks of age and has better results than a urine
test. A urine test may be done to check phenylalanine levels during treatment
with low-protein foods.
If your baby has PKU, a special low-protein
diet is needed to prevent
intellectual disability. Your baby will drink milk
substitutes that do not contain phenylalanine. People with PKU need to stay on a low-protein diet for
life to prevent problems.
U.S. Preventive Services Task Force (2008). Screening for phenylketonuria (PKU). Available online: http://www.uspreventiveservicestaskforce.org/uspstf/uspsspku.htm.
Chernecky CC, Berger BJ (2013). Laboratory Tests and Diagnostic Procedures, 6th ed. St. Louis: Saunders.
Other Works Consulted
Committee on Genetics, American Academy of Pediatrics (2008). Maternal phenylketonuria. Pediatrics, 122(2): 445–449.
Fischbach FT, Dunning MB III, eds. (2009).
Manual of Laboratory and Diagnostic Tests, 8th ed.
Philadelphia: Lippincott Williams and Wilkins.
March of Dimes (2013). Birth defects: PKU in your baby. Available online: http://www.marchofdimes.com/baby/birthdefects_pku.html.
Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.