Neonatal screening test

How is the test done?

How often are these problems found?

How accurate are the tests?

Phenylketonuria (PKU) and other amino acid metabolism disorders

Galactosaemia

Congenital hypothyroidism

Cystic fibrosis

Fatty acid oxidation defects (FAOD)

Lysosomal storage diseases (LSDs)

Antenatal screening tests

 

Babies born have a blood test taken when they are about 48 hours old. This test is the Neonatal Screening Test, also called the Newborn screening test, 'Guthrie' test, or 'heel prick' test. The test can tell if a baby has one of many rare but serious health problems before any harm is done and even before there are signs that there is a health problem.

Finding these problems early means that the children can have treatment which can lessen, or prevent, harm from the problems.

How is the test done?

When a baby is about 2 days old a health care worker, usually a midwife, will collect some blood from each baby by pricking the heel of the baby and catching the blood on four spots on special test paper.

• If the baby goes home from hospital before the test is done, it may be
  done by the home visiting midwife, or the parents may be asked to bring the
  baby back to the hospital for the test.
• Over 30 different health problems can be detected using these blood
  spots.
• The blood spots are tested for Phenylketonuria (PKU), Galactosaemia, Congenital Hypothyroidism, Cystic Fibrosis (CF), and several conditions affecting the breakdown of fats (fatty acid oxygenation defects (FAOD) and proteins (amino acid metabolism disorders).
• If this test suggests that there may be a problem the parents are contacted
  and further tests will be arranged.
• Great care is taken to make sure that each test which shows that there may
  be a problem is followed up, but if you have concerns that you do not know the result of your baby's test you can contact your birth centre to find out the result.
• Most of the children who are found to have these problems will need specialised support, usually through a major children's hospital.

How often are these problems found?

• Each of these health problems is rare, but added together, about one in 800 newborn babies will be found to have one of these health problems.

How accurate are the tests?

• There is an extremely rare form of congenital hypothroidism that the test finds in many but not all cases. Children with this often have other problems which suggest the possibility of this form of congenital hypothyroidism.
• Testing for CF is approximately 95% accurate. The tests recently added have also been found to be very accurate.
• Occasionally a test needs to be done again because there were difficulties with how the blood was collected or the baby was sick at the time. Most of these repeat tests will be found to be normal.

Phenylketonuria (PKU) and other amino acid metabolism disorders

These are a group of inherited health problems related to defects in the breakdown of amino acids (building blocks of protein).

• PKU is the most common one. The baby cannot break down the amino acid called phenylalanine.
• High levels of phenylalanine and other chemicals formed from it will cause damage to the brain.
• A baby with the problem is normal at birth, but within a few months will have obvious brain damage.
• If they are fed a special diet these babies will have normal intelligence and be healthy. You will get information about this if your baby has a problem.
• Dr Robert Guthrie invented the Guthrie test in the USA to find PKU.
• As well Phenylketonuria (PKU), other genetic problems (such as maple syrup urine disease and homocystinuria) can affect the way proteins and changed into amino acids.
• These conditions are rare, but can be life threatening.
• In almost all cases, if children with these conditions are fed a special diet from soon after birth, they will be healthy and have normal intelligence

Further information

• MedlinePlus, National Library of Medicine (USA)
• National PKU News - Brummitt, Jane 'Robin and I explain PKU'

Galactosaemia

• Galactose is a sugar (carbohydrate).
• In the body lactose (one of the sugars in milk) is changed into galactose and glucose.
• In Galactosaemia, galactose cannot be properly broken down, and the high levels cause brain and liver damage, cataracts and other health problems.
• If the problem is found very early, most of the health problems can be prevented with a special diet.

Congenital hypothyroidism

• Congenital hypothyroidism arises when a baby does not make enough thyroid hormone. The baby's thyroid gland (in the neck) may make a little of the hormone, or may make none.
• The health problems are not usually obvious at birth, but with time there is a delay in brain development which usually does not improve with later treatment.
• If treatment with extra thyroid hormone is started early, children with congenital hypothyroidism grow and develop normally.

Cystic fibrosis

• Cystic Fibrosis (CF) is an inherited problem which mostly affects the lungs (sticky mucous) and gut (affecting the way food is absorbed).
• Children and young people with CF usually get a lot of severe chest infections, and digestion problems.
• CF does not affect brain development.
• Many people in Australia (about 1 in 25) carry a gene which can cause CF (they are called 'carriers'), but a person needs two genes to have the disease.
• The blood test will find about 96% of children who have two genes for CF (ie they have the health problem) and also many children who have only one gene (the 'carriers' who do not have the health problems). An extra test (a sweat test) is needed to find out which children have the disease. About 1 in 12 of the children who need this extra test will have CF.
• Finding the disease early has been shown to improve the life of children with CF, although it does not prevent all of the problems.

Further information

• MedlinePlus, National Library of Medicine (USA)

Fatty acid oxidation defects (FAOD)

Fatty acid oxidation (breakdown) defects are a newly recognised group of disorders, discovered in the 1980s. Fatty acid oxidation defects can cause problems such as low blood sugar, and can be fatal if not diagnosed and treated.

Children with fatty acid oxidation defects are generally well unless they have a virus infection (cold or flu) or go for longer than usual between feeds or meals.

Treatment usually involves avoiding long fasting (eg feeding may be needed during the night).

Lysosomal storage diseases (LSDs)

• LSDs are rare congenital diseases where there is a problems with the way cells 'recycle' some chemicals, so that they build up in the cells. Some cause developmental delay and others cause different health, growth and development problems.
• Finding these problems early will enable these babies to be supported and the health problems cared for more effectively.
• LSDs affect 1 in 7,700 births.

Antenatal screening tests

In a small number of pregnancies a baby may not develop normally. Neural tube defects (causing spina bifida and hydrocephalus) and Down syndrome both occur early in a baby's development and each may be detected before the baby's birth by 'antenatal' tests ('ante' means before, and 'natal' means birth).

Children with each of these problems will each need to be supported within a specialised paediatric unit.

Further information

For further information about neonatal screening:

• Australasian Referral Laboratory for Lysosomal, Peroxisomal and related genetic disorders.