Newborn screening

Current UK newborn screening

The newborn and 6- to 8-week infant physical examinations

Mothers of all infants are offered two screening physical examinations of their babies, one within the first 72 hours of birth and the second at 6-8 weeks of age. Like the mid-pregnancy ultrasound scan, this is a general examination which can detect a wide range of physical problems and can be used to screen for conditions such as:

• Congenital cataracts - by ophthalmoscope examination.

• Congenital heart disease - by examination of the cardiovascular system.

• Undescended testes - by palpation of the scrotum and inguinal canals.

• Developmental dysplasia of the hip - by the Barlow and Ortolani tests and examination of the lower limbs for asymmetry or limited abduction.

See also the articles on Neonatal Examination, Hearing Testing and Screening in Young Children and Six-week Baby Check.

Newborn hearing screening

Parents are offered a hearing screen for their baby within 4-5 weeks of birth. The screen is usually carried out before discharge from hospital, but in some areas it is carried out in the home.

The first test offered is the Automated Oto-acoustic Emission (AOAE) screening test. This involves placing a soft-tipped probe into the baby's ears, playing sounds and trying to detect a response - 'echo' - from the baby's cochlea.

Well babies who do not have a clear response to this test (this is called a 'no clear response') are referred for an Automated Auditory Brainstem Response (AABR) screening test.

The AABR test involves playing sounds to the baby and trying to detect responses from their brainstem via electrodes placed on the baby's head and neck. It measures not only the integrity of the inner ear, but also the auditory pathway. It can therefore detect the rare condition of auditory neuropathy in children who are deaf but have normal oto-acoustic emissions (because the cochlea is normal).

Babies who have spent more than 48 hours in a Neonatal Intensive Care Unit (NICU) or Special Care Baby Unit (SCBU) are regarded as high-risk and are screened using both AOAE and AABR tests, except in Wales and some areas of Scotland where they are screened using the AABR test only.

Any baby referred from the Newborn Hearing Screen should be seen for full audiological assessment within four weeks of screen completion.

Newborn blood spot screening

Mothers of all newborn babies are offered testing for the following conditions by testing a blood spot taken from the baby (often referred to as the 'heel prick' and previously known as the 'Guthrie' test) at 5-8 days of life (ideally on day 5). For many of these disorders early detection can be critical. See the links for further information about each condition.

• Phenylketonuria (PKU):
  

  • Current tests look for a combination of total biopterin and dihydropteridine reductase from neonatal blood spots.

  • The original 'Guthrie' test (semi-quantitative and difficult to automate) is being gradually superseded by chromatography, fluorometry or mass spectrometry.

  • Newborn screening allows early implementation of the phenylalanine-restricted diet, eliminating the severe neurocognitive and neuromotor impairment associated with untreated PKU.¹

• Congenital hypothyroidism:
  

  • Currently established on the same blood spot sample as above.

  • Babies born at less than 32 weeks of gestation (less than or equal to 31 + 6 days) will need a repeat test. The repeat test should be done at 28 days of postnatal age, counting the original expected date of birth as day 0, or the date of discharge home, whichever is the sooner.

  • The outlook for this preventable cause of growth restriction and mental handicap has been transformed by newborn screening.²

• Sickle cell disease:
  

  • The form of screening for haemoglobin variants depends on the prevalence of the condition.

  • The programme allows the offer of sickle cell screening to all infants as an integral part of the newborn blood spot screening.³

  • Early diagnosis can lead to sickle cell disease-related morbidity rates decreasing, such as overt stroke.⁴

• Cystic fibrosis (CF):
  

  • Biochemical screening is now universal. Initial screening detects raised levels of immunoreactive trypsinogen (IRT), which is then followed by DNA analysis.

  • The most common mutation is in the DF508 gene in 95% of affected individuals in the UK.

  • Neonatal screening has significantly reduced the age of diagnosis of CF. However, a small number of patients with CF can still be missed by the screening programme and the diagnosis should be considered even with a negative screen result.⁵

• Medium-chain acyl-CoA dehydrogenase deficiency (MCADD):
  

  • A rare genetic but treatable inherited metabolic disorder that prevents the normal breakdown of fat.

  • MCADD becomes a problem during prolonged fasting and illness because fat cannot be broken down quickly enough and harmful substances build up.

  • Untreated MCADD can cause serious illness, and can be life threatening, but with newborn screening and early treatment this can be prevented.

• Homocystinuria:
  

  • Affected individuals appear normal at birth but develop serious complications in childhood.

  • Diagnosis and treatment started sufficiently early in life can effectively prevent or reduce the severity of these complications.⁶

• Maple syrup urine disease (MSUD):
  

  • MSUD is an autosomal recessive disorder which can be caused by mutation in at least four genes.

  • Accumulation of leucine, isoleucine and valine and their corresponding ketoacids leads to encephalopathy and progressive neurodegeneration in an affected patient. The brain injury is irreversible if not diagnosed and managed early in life.⁷

• Glutaric aciduria type 1:
  

  • Glutaric aciduria occurs in approximately 1 in 109,000 infants worldwide.

  • It is an autosomal recessive disorder usually caused by a homozygous or heterozygous compound mutation in the gene encoding glutaryl-CoA dehydrogenase on chromosome 19p13.

  • Gliosis and neuronal loss in the basal ganglia lead to a progressive neurodegenerative and movement disorder that usually begins in the first year.

  • Untreated infants characteristically develop dystonia, resulting in a high morbidity and mortality. Initiation of treatment after the onset of symptoms is generally not effective in preventing permanent damage and so early diagnosis is essential.⁸

• Isovaleric acidaemia:
  

  • This is caused by a mutation in the isovaleryl-CoA dehydrogenase gene. Accumulation of isovaleric acid (which is toxic to the central nervous system) causes symptoms.

  • There are two forms; an acute neonatal form which leads to massive metabolic acidosis and rapid death, and the chronic form in which there are periodic attacks of severe ketoacidosis and intervening asymptomatic periods.

  • It is closely related to MSUD in metabolic pathway.

  • Management includes giving glycine and restricting leucine.

• UK variation exists within the blood spot. Further information can be found at the NHS Newborn Blood Spot Screening Programme's 'Resources for health professionals'.⁹

• Parents can decline one or all of the tests included on the blood spot.

• It is important that parents be given time to make a decision regarding the heel prick test (eg, by providing information during pregnancy, emphasising the decision-making aspect and clearly articulating the reasons behind screening) to ensure that they feel they have made an informed choice.¹⁰

Possibilities for future newborn screening programmes

The UK National Screening Committee (UK NSC) has over a hundred screening policies for conditions ranging from anaemia in pregnancy to vision in adults. Sometimes the UK NSC will recommend that screening for a condition should be offered and other times that, based on the current available evidence, screening should not be offered.

All the policies are available in the UK NSC's policy database (see 'Further Reading' below).

New evidence from research is being published all the time and it might be that, even if screening for a condition could not be recommended in the past, new evidence suggests otherwise. This means that it is important for the UK NSC to review all its policies on a regular basis.