Testing & Diagnosis for Phenylketonuria (PKU) in Children

Newborn screening for PKU is required in all 50 states of the United States. This is because treatment needs to begin within the first weeks of life in order for the child to live a full life. A baby that tests positive for PKU by newborn screening may be referred to Children’s by their primary care doctor. At the hospital, blood and urine tests will be conducted to determine the exact type of PKU and the treatment needed.

Newborn Screening

  • It is the first level of testing.
  • New England Newborn Screening Program screens all babies in New England
  • Testing occurs within two days after birth.
  • High phenylalanine with low tyrosine levels indicates PKU.
  • Babies testing positive for PKU have their results sent to a physician who refers the baby to Boston Children’s, or a hospital like Boston Children’s, for confirmation.

Metabolic disorder blood test

  • It’s used to confirm the Newborn Screening test results.
  • It’s conducted by the Metabolism Program at Boston Children’s.
  • A needle is used to draw blood from the baby’s arm.
  • Test is done within the first week after birth, or earlier.
  • Analyzes the levels of amino acids, including phenylalanine and tyrosine.
  • High levels of phenylalanine indicate PKU.
  • A urine specimen is collected by applying a special collection bag to the baby’s bottom.