How do they test for PKU in newborns?

A PKU test is done a day or two after your baby’s birth. The test is done after your baby is 24 hours old and after your baby has ingested some protein in the diet to ensure accurate results. A nurse or lab technician collects a few drops of blood from your baby’s heel or the bend in your baby’s arm.

How is the PKU test performed?

The blood sample for PKU is usually taken from your baby’s heel (called a heel stick). The test is done in the first few days after birth, as early as 24 hours after birth. The test may be repeated within the first week or two after birth.

Can newborn screening detect phenylketonuria?

Diagnosing PKU

At around 5 days old, babies are offered newborn blood spot screening to test for PKU and many other conditions. This involves pricking your baby’s heel to collect drops of blood to test. If PKU is confirmed, treatment will be given straight away to reduce the risk of serious complications.

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What happens if a baby tests positive for PKU?

Newborn babies who test positive for PKU are placed on phenylalanine-free formula right away. As babies start to eat solid food, their diet will need to be restricted. This is because phenylalanine is found in many foods with protein. A child with PKU should not eat milk, fish, cheese, nuts, beans, or meat.

Does the PKU test hurt?

Most babies experience some brief discomfort from the heel stickWhen the baby’s heel is pricked to collect a sample of blood for newborn screening, but it heals quickly and leaves no scar.

Is PKU test necessary?

Although PKU is rare, all newborns in the United States are required to get a PKU test. The test is easy, with virtually no health risk. But it can save a baby from lifelong brain damage and/or other serious health problems. If PKU is found early, following a special, low-protein/low-Phe diet can prevent complications.

How long does PKU test take?

The newborn screening test will be repeated and additional tests will be done to help the doctors figure out if your baby has PKU. Usually the results of these tests take a few days to come back.

How sensitive is the newborn screening for PKU?

The sensitivity of the screening test was 99.2% for infants with classical and mild PKU.

What tests are done newborn?

Newborn screening is a public health service done in each U.S. state. Every newborn is tested for a group of health disorders that aren’t otherwise found at birth. With a simple blood test, doctors can check for rare genetic, hormone-related, and metabolic conditions that can cause serious health problems.

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What tests are done on newborns after birth?

The most common newborn screening tests in the US include those for hypothyrodism (underactivity of the thyroid gland), PKU (phenylketonuria), galactosemia, and sickle cell disease. Testing for hypothyroidism and PKU is required in virtually all States.

What disorders does PKU test for?

This is a blood test to screen newborns for phenylketonuria (PKU), a condition that can cause brain damage and severe intellectual disability if it goes untreated. The problems often appear in the first year of life, causing infants to appear abnormally sleepy and listless.

What are the signs that lead doctors to diagnose an infant with phenylketonuria?


  • A musty odor in the breath, skin or urine, caused by too much phenylalanine in the body.
  • Neurological problems that may include seizures.
  • Skin rashes (eczema)
  • Fair skin and blue eyes, because phenylalanine can’t transform into melanin — the pigment responsible for hair and skin tone.

Can babies with PKU breastfeed?

In the early 1980s, with the determination of low concentration of Phe in breast milk, breast milk supplemented with Phe-free formula has become an acceptable dietary treatment for infants with PKU. Today, breastfeeding is encouraged and well established in PKU patients.

How often are PKU tests wrong?

Although initial PKU screening demonstrates positive results in 1 percent of infants, there is only a 10 percent chance that an infant with an initial positive result has the disorder (false-positive rate of 90 percent). 6 A repeat test must be performed if the initial test is positive. False-negative results are rare.

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Where should an infant’s skin be punctured for a PKU test?

An area of the infant’s skin, most often the heel, is cleaned with a germ killer and punctured with a sharp needle or a lancet. Three drops of blood are placed in 3 separate test circles on a piece of paper. Cotton or a bandage may be applied to the puncture site if it is still bleeding after the blood drops are taken.