Phenylketonuria (PKU) Screening
Reviewed
Screening test for phenylketonuria (PKU) in newborns, measuring phenylalanine (Phe) levels in blood. A screen-negative result means lower likelihood of PKU; a screen-positive result means higher likelihood and requires prompt confirmatory testing. Early detection and dietary management can prevent lifelong brain damage.
Preparation and collection
No special preparation needed. For accurate results, the baby should have had some protein from breast milk or formula before the test.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- The test is a screening, not a definitive diagnosis. Further testing is needed to confirm or rule out PKU.
- If performed before 24 hours after birth, a repeat test at 1-2 weeks of age may be necessary.
- There is a small risk of false positives or negatives; results should be interpreted by a healthcare professional.
What to do next
Discuss results with your baby's healthcare provider. If screen-positive, prompt follow-up for confirmatory testing and potential dietary management. If screen-negative but both parents are known carriers, genetic testing may be recommended.
Evidence source
U.S. National Library of Medicine: Phenylketonuria (PKU) Screening