Screening tests for newborns


Screening newborn babies using laboratory blood tests is important for the early diagnosis and treatment of certain rare genetic and congenital disorders. This is usually done within a few days of birth when the disorders would otherwise not be clinically apparent at this early age.

The vast majority of screening tests will be normal and most babies screened will not have any of the conditions tested for but, for the small number that do, the benefits of screening are enormous. Early treatment can improve their health and prevent severe disability or even death.

For these tests, a few drops of blood from a heel prick are soaked into a special card (dried blood spots), which is then sent to a specialist screening laboratory for testing. For babies with abnormal results (screen positive) the family will be contacted by a health professional and invited to meet a special clinical team so that the screening result can be confirmed, and if follow-up tests are positive, appropriate management/ treatment can be started without delay.

It is important to understand that not all cases of the disorders screened for will be picked up – in a very few cases false negative screening test will occur. Positive screen results can also be false positive results, and further testing may show the newborn baby does not have the disease.


General Sources


Related links
Healthdirect Australia: Neonatal Diseases
Healthdirect Australia: Genetic Diseases and Disorders
NSW Health - Centre for Genetics Education: Newborn screening


Common metabolic and genetic tests

Screening newborns is important for the early detection, diagnosis, and treatment of certain genetic, metabolic, and infectious diseases. This is usually done within a few days of birth. Screening is currently recommended for visual problems, hearing problems, congenital heart disease, detection of congenital malformations, delayed descent of testicles, and dislocation of the hip.

Laboratory testing is used throughout Australia for screening for the detection of a number of congenital metabolic diseases.

There are five centralised screening laboratories in Australia that cover all the states and territories. Newborns are currently routinely screened, by heelprick bloodspot testing for a number of metabolic and genetic defects. The three major diseases screened for are:

In addition to these disorders the programs screen for galactosaemia and up to 30 other very rare disorders that affect the processing of fatty acids, organic acids and amino acids.

Newborns who have certain symptoms or who are born to mothers who may have been exposed to certain pathogens may have a TORCH screen performed. TORCH is an abbreviation for the infections tested for: Toxoplasmosis, Other (including syphilis, varicella zoster, parvovirus), Rubella, Cytomegalovirus, and Herpes simplex virus. These infections are not serious for the mother but account for 2-3% of congenital disability.

Other screening


Related links

Healthdirect Australia: Neonatal Diseases
Healthdirect Australia: Genetic Diseases and Disorders
NSW Centre for Genetics Education: Newborn screening


Congenital hypothyroidism

Congenital hypothyroidism occurs when an infant is born with a thyroid gland that is not producing enough thyroid hormones. Untreated congenital hypothyroidism may cause mental retardation.

Screening for this condition involves looking for a high level of the hormone TSH in the baby’s blood. Blood is normally sampled from the baby’s heel ('heelprick') and collected onto a piece of card (Guthrie card). Several spots of blood can be collected at the same time to allow screening for other conditions, such as phenylketonuria (PKU).

If the thyroid testing results indicate congenital hypothyroidism, thyroid hormone supplements may be necessary.


Phenylketonuria

Inheritance of this disorder results in a build-up of phenylalanine (a protein component) in the blood. It may cause developmental delays, seizures, severe mental retardation, and an unusual mousy odour. Diagnosis is made by routine screening of all babies.

Blood is collected onto a piece of card (Guthrie card), and several spots can be collected at the same time to allow screening for other conditions, such as congenital hypothyroidism. For the diagnosis of PKU, blood phenylalanine concentration is measured.

The condition is controlled by restricting phenylalanine in the diet as soon as possible and certainly, before four weeks of age to avoid permanent brain damage. This dietary restriction must continue throughout the patient's life.

Limitation of PKU test
Collection of an insufficient amount of specimen will affect the test result. The child should be taking a normal diet to prevent an inaccurate result.


Cystic fibrosis

Cystic fibrosis (CF) is a relatively common inherited disease in which from infancy there are recurrent chest infections causing lung damage, intestinal malabsorption leading to severe malnutrition and growth failure, and an excess of salt in the sweat. Untreated, the condition is usually fatal in infancy or early childhood. With modern treatment affected children now have a median survival of 30 years.

For more information see: Cystic fibrosis.


Galactosaemia

This is an inherited disorder that results in the inability to break down the sugar galactose, which is found in all milk and milk products. Within the first two weeks of life, untreated infants born with this condition experience vomiting, liver disease, mental retardation and poor growth, which may result in death. Diagnosis is usually confirmed by measuring the activity of the enzyme that is normally deficient in this condition (galactose-1-phosphate uridyl transferase).

Treatment is a lifelong galactose (and therefore milk) free diet.


Blood type and direct antiglobulin test

These are not screening tests but are appropriate in neonates in the following situations:

  1. When the mother is group O blood type
  2. When the mother is Rh-negative
  3. When the mother’s blood has an antibody that could be harmful to the baby
  4. When the baby has clinical symptoms that might be explained by the results of these tests.

There are two main reasons to perform these tests on a newborn. The first is to determine if an Rh-negative mother should receive 'anti-D gamma globulin' after delivery. This treatment helps prevent the development of antibodies in the mother that could be harmful to a baby in future pregnancies. Only Rh-negative mothers of Rh-positive infants receive the treatment.

The second reason to perform these tests is to identify newborns that may be at risk of anaemia due to harmful antibodies from the mother's blood. For example, babies with either group A or B blood type may react with antibodies produced by mothers with group O blood type. A direct antiglobulin (Coombs') test is used to determine if the mother’s antibodies have reacted with the baby’s blood cells.

A negative test usually means that the mother’s antibodies are not affecting the baby’s blood and the infant is not at risk. A positive test means the baby is at risk of developing anaemia. Many reactions to maternal antibodies produce only mild symptoms in the newborn. Some reactions, however, can cause moderate to severe anaemia, brain damage and death.

A positive direct antiglobulin test does not necessarily mean the baby will develop anaemia.