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This article waslast modified on 22 September 2017.

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 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.

Common Metabolic & Genetic Tests
  • Overview

    These programmes are overseen by the UK National Screening Committee (NSC) which currently recommends that all babies in the UK are offered screening at 5 – 8 days of age for:

    • phenylketonuria (PKU)
    • congenital hypothyroidism (CHT)
    • sickle cell disorders (SCD)
    • cystic fibrosis (CF)
    • Medium-chain acyl-CoA dehydrogenase deficiency (MCADD)
    • Maple syrup urine disease (MSUD)
    • Isovaleric acidaemia (IVA)
    • Glutaric aciduria type 1 (GA1)
    • Homocystinuria (pyridoxine unresponsive) (HCU)
    • Blood type and direct antiglobulin test

     

    The UK Newborn Screening Programme Centre has responsibility for developing, implementing and maintaining the blood spot programme.

    Other Conditions detected
    Using these screening tests, very rarely other disorders may be detected. Unusual haemoglogbin disorders and other conditions such as beta thalassaemia major may be identified. In this condition, the baby does not make enough red blood cells, and needs treatment for severe anaemia. Some disorders which cause liver disease may be detected from the PKU programme. Both the CF programme and the Sickle programme will detect some carriers.Carriers are healthy and will not be affected by the condition.

    Other Disorders
    It is possible to screen for other disorders using the same dried blood spot but this is currently not recommended in the UK. The NSC keeps under the review the case for screening for other conditions – see UK National Screening Committee Portal

  • Phenylketonuria (PKU)

    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. Normally a midwife or health visitor will collect a sample of blood from a baby’s heel ('heelprick') between six and ten days of age. 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.

  • Congenital Hypothyroidism

    About 1 in 4,000 babies born in the UK has congenital hypothyroidism (CHT). Babies with CHT do not have enough of the hormone thyroxine. The commonest cause of CHT is a poorly developed or absent thyroid gland .The screening test is measurement of thyroid stimulating hormone (TSH). Without thyroxine, babies do not grow properly and can develop serious, permanent, physical and mental disability. Screening means that babies with CHT can be treated early with thyroxine tablets, which will prevent serious disability and allow them to develop normally. If babies are not screened and are later found to have CHT, it may be too late to prevent them becoming seriously disabled.
    These thyroid defects may be permanent or transient. Although the baby with CHT should be started on thyroxine promptly, they should be evaluated at some time later to exclude a transient problem.

  • Sickle Cell Disorders

    About 1 in 2,500 babies born in the UK has a sickle cell disorder (SCD). These are inherited disorders that affect the red blood cells. If a baby has a sickle cell disorder, their red blood cells can change to a sickle shape and become stuck in the small blood vessels. The screening test looks at the types of haemoglobin in the baby’s blood. SCD can cause pain and damage to the baby’s body, serious infection, or even death. Screening means that babies with SCD can receive early treatment, including immunisations and antibiotics, which, along with parent education, will help prevent serious illness and allow the child to live a healthier life.

  • Cystic Fibrosis

    About 1 in 2,500 babies born in the UK has cystic fibrosis (CF). This inherited condition can affect the digestion and lungs. Babies with CF may not gain weight well, and have frequent chest infections. The screening test measures immunoreactive trypsinogen in the blood spot. Screening means that babies with CF can be treated early with a high energy diet, medicines and physiotherapy. Although a child with CF may still become very ill, early treatment is thought to help them live longer, healthier lives. If babies are not screened for CF and the condition is suspected they can be tested later, usually with a sweat test.

     

     

  • MCADD

    About 1 in 10,000 babies born in the UK has MCADD. Babies with this inherited condition have problems breaking down fats to make energy for the body. This can lead to serious illness, or even death. The screening test measures a partially broken down fat called octanoyl carnitine(c8).  Screening means that most babies who have MCADD can be recognised early, allowing special attention to be given to their diet, including making sure they eat regularly. This care can prevent serious illness and allow babies with MCADD to develop normally.

     

     

  • Blood Typing and Direct Antiglobulin Test (Coombs') Test

    These tests 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. As described earlier, 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.