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Health Professionals Guide to Newborn Screening
Phenylketonuria (PKU)
(Hyperphenyalaninemia and Biopterin Cofactor defects of regeneration and biosynthesis)
Autosomal recessive hyperphenylalanemia caused primarily by a deficiency of phenylalanine hydroxylase activity or impaired synthesis or recycling of the biopterin (BN4) cofactor. Early detection and treatment is essential to prevent associated mental retardation.
| Prevalence (WI): |
1:16,200 |
| Analyte Measured: |
Phenylalanine (Quantitative) |
| Abnormal Levels: |
³ 150 µmol/L |
| Feeding Effect: |
Minimal (See comment below.) |
| Timing Effect: |
< 24 hours of age: Repeat at two weeks
³ 24 hours of age: Results are valid |
| Confirmation: |
Repeat newborn screen. If repeat result is greater than first result, contact a metabolic clinic.
NOTE: If initial result is greater than 1210 µmol/L, contact metabolic clinic immediately. |
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Treatment: |
The mainstay of treatment for PKU is the low-phenylalanine diet. Treatment should begin as soon after birth as possible and be continued throughout life. Low phenylalanine infant formulas are available from the state's metabolic clinics. |
COMMENT: The use of quantitative phenylalanine measurements increases the ability to detect PKU earlier in the baby’s life than previously used qualitative assays. This, and the fact that phenylalanine levels are often (greater than 90% of the time) above normal at birth and continue to rise in the first hours of life, decrease the need for a protein feeding for the detection of PKU. The program has detected PKU in babies when specimens were collected before 8 hours of age and prior to a protein feeding.
Information on treatment centers is also available on this site.
For information about other screened disorders, click on the next page button, or follow one of these links:
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