Phenylketonuria (PKU) Screening
A PKU screening test measures the amount of a protein called phenylalanine (Phe) in a sample of a newborn's blood.
A PKU screening test measures the amount of a protein called phenylalanine (Phe) in a sample of a newborn's blood. Phe is in all foods that contain protein such as milk, meats, and nuts. It's also in an artificial sweetener called aspartame. If a newborn has high levels of Phe in their blood, it could mean that they have phenylketonuria (PKU). PKU is a rare genetic disorder , meaning it's caused by changes (also called variants or mutations) in a gene. Genes are parts of DNA in your cells that you inherit from your parents. You inherit two copies of each gene, one from each parent. Genes carry information that controls what you look like and how your body works. The gene involved in PKU helps make a substance that breaks down part of Phe in food. So, a change in that gene can make it harder for your body to break Phe down. This means that if you have PKU and eat foods with Phe, the Phe will build up in your blood. High levels of Phe can permanently damage your nervous system and brain, leading to various health problems such as seizures and possibly learning disabilities . PKU can vary from mild to severe, depending on whether the changed gene still works somewhat or has stopped working completely. Other names: PKU newborn screening, PKU test
Clinical Interpretation
If the results are normal , it means that the amount of Phe in your baby's blood was normal. So, your baby is unlikely to have PKU. But if the test was done sooner than 24 hours after birth, your baby may need to be tested again at 1 to 2 weeks of age. If both parents know they carry a gene for PKU and your baby's test is normal, the baby should have genetic testing . This blood test will check the baby's genes for changes. The results will diagnose PKU or rule it out for certain. If your baby does have PKU, genetic testing can also help your provider understand how serious the condition is and how best to treat it. If your baby's results are not normal , it means high levels of Phe were found in your baby's blood. Your baby most likely has PKU. Your provider may order more tests to confirm or rule out PKU. These tests may include more blood tests and/or urine tests . If your baby is diagnosed with PKU, you can safely give your baby formula that doesn't contain Phe. Breastmilk does contain Phe, so if you would like to breastfeed, talk with your baby's provider to find out if your baby can safely have any amount of breastmilk. After infancy, people with PKU are generally treated with a special-low protein diet, including some food supplements, to make sure they have proper nutrition . Learn more about laboratory tests, reference ranges, and understanding results .
Clinical Protocol & Patient Advice
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There are no special preparations needed for a PKU test.
Usage Guidance
- Reference ranges vary by laboratory. Always discuss your specific results with a qualified healthcare professional.
Source: MedlinePlus, National Library of Medicine. View the original.