Newborn screening tests
Newborn screening — a worldwide program
Newborn screening tests are part of a worldwide practice to detect rare but serious health problems (genetic or metabolic disorders) in newborn babies. Early diagnosis of these conditions enables treatment to begin at the earliest opportunity and reduces the ill effects of these disorders throughout life. Publicly funded screening of newborn babies has been available in Australia since the late 1960s.
How is newborn screening carried out?
The newborn screening test sample is normally collected by a midwife, using the ‘heel prick’ test. A few drops of blood are taken from your baby’s heel and collected onto a special card called a Guthrie card. The dried blood sample is then sent to the local screening laboratory for testing. The test is performed between 48 and 72 hours after the birth. If you have your baby at home or leave hospital within 48 hours, a midwife may collect your baby’s blood sample at home approximately 4 days after the birth.
Soon after your baby is born, a newborn hearing test will also be offered. Although only one or 2 in every 1000 babies in Australia has a significant hearing deficiency, early identification means the parents of these infants can have access to the services they need as soon as possible. Your baby may be tested while you are in hospital, or testing may be done at an outpatient clinic or local community centre.
Which conditions are tested as part of newborn screening?
For several decades, babies have been screened for phenylketonuria, congenital hypothyroidism, cystic fibrosis and galactosaemia. However, recent developments in technology (tandem mass spectrometry) mean that over 30 different disorders can now be detected using the blood spot tests, including disorders of fat metabolism.
Phenylketonuria is a rare condition affecting about one in 15,000 babies in Australia. It is the most common amino acid metabolism disorder. (Amino acids are the building blocks of proteins.) It occurs when a baby is unable to break down phenylalanine, an amino acid. If left untreated, phenylketonuria causes high levels of phenylalanine to accumulate in the blood, resulting in severe brain damage. Detection of phenylketonuria at birth means that babies can be treated with special milk, and eventually a special diet, which allow them to grow and develop normally.
Congenital hypothyroidism affects about one in 3300 babies in Australia. It occurs when the thyroid gland is absent, is too small, or does not produce enough thyroid hormone. If untreated, it can lead to poor growth and development. Treatment with a daily thyroid hormone tablet allows affected children to grow and develop normally.
Cystic fibrosis occurs in about one in 2500 babies in Australia. It is an inherited condition that causes the body to produce thicker than normal mucus in the lungs and digestive tract. Affected children have problems digesting and absorbing food and are prone to serious chest infections.
The heel prick test determines whether the amount of a digestive enzyme (a chemical produced by the body to help food digestion) is abnormal. Early detection, combined with advances in medical treatment, has significantly improved the lives of babies with cystic fibrosis. However, it is rare but possible that not all the genetic changes that cause cystic fibrosis will be picked up on initial testing. Therefore, you should seek medical advice if your baby is failing to gain weight properly, having frequent chest infections or passing frequent bulky, foul-smelling, oily stools.
Galactosaemia is a very rare disorder affecting about one in 40,000 babies in Australia. It is caused by an accumulation of galactose (a type of sugar found in both breast and cow's milk) in the blood. Serious illness can be prevented when this condition is detected early and babies are given a specially formulated milk.
Disorders of fat metabolism (fatty acid oxidation defects)
These disorders are rare, but once they are detected, they can usually be treated by modifying the baby’s diet.
How do I get the results of the tests?
The results of the screening tests are usually returned to your doctor or midwife within a week. The exact timing and how the results are returned depend on which state you live in. You will only be contacted if there are concerns about your baby’s test results. About one in 100 babies needs a second test because the results are inconclusive. Most second tests give normal results, and your doctor or midwife will be notified accordingly. If the test is positive for any of the conditions being tested, your doctor or midwife or the test centre will contact you to arrange an appointment for further tests.
What if I don’t want my baby to be tested?
Screening is not compulsory in Australia, therefore you have the right to refuse the tests on your baby’s behalf. If you refuse the newborn screening tests you may be asked to discuss the situation with a genetic counsellor and you may be asked to sign a written statement showing that you understand the potential risk to the healthy development of your baby.
2. Centre for Genetics Education. The Australasian Genetics Resource Book: newborn screening for genetic conditions. Sydney: Centre for Genetics Education, June 2007. Available from: http://www.genetics.edu.au/Information/Genetics-Fact-Sheets/NewbornScreeningforGeneticConditionsFS20 (accessed 3 September 2012).