Phenylketonuria (PKU) screening is a blood test done to determine whether a newborn has the enzyme to metabolize phenylalanine. Phenylalanine is an amino acid that is needed for normal growth and development. It is found in most foods containing protein, especially milk, cheese, and meats. PKU is an inherited disease caused by the absence of the enzyme that converts excess phenylalanine into another amino acid called tyrosine.
When the phenylalanine level builds up in a baby's blood, it can cause brain damage, seizures, and mental retardation. The damage caused by PKU can begin within weeks after the baby has started drinking breast milk or formula. Babies with PKU need foods low in phenylalanine to prevent severe brain damage.
It is important to diagnose this disease early. All babies in the United States are now tested for PKU shortly after birth. It is estimated that about 1 in 14,000 to 1 in 20,000 babies have PKU. 1 In the United States, PKU occurs more frequently in whites and Native Americans and is less common in blacks, Hispanics, and Asians.
The blood sample for PKU is usually taken from your baby's heel (called a heel stick) within 2 to 3 days after birth. A urine PKU test is done on a baby who did not have a blood test and who is older than 6 weeks.
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One heel stick and we obtain 5 drops of blood. The test is then sent to the State Metabolic Unit for evaluation. Results typically take 10 days to get back.
PKU Test
