Approximately 840 children are born deaf in both ears each year in the UK. Some 90% of these babies are born into families with no experience or history of childhood deafness.
The Newborn Hearing Screening Programme was introduced in the UK in 2006, replacing the previous infant screening programme (the 'distraction test' at 8 months). Most congenitally deaf children are now identified and managed appropriately before 6 months of age.
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Rationale for screening
- Hearing loss is not confined to those with risk factors - approximately 40% of all children ultimately identified with sensorineural hearing loss do not have an established risk factor; therefore, universal screening is recommended.
- Hearing screening allows hearing loss to be identified at a younger age. There is evidence that this is beneficial because early detection and management improve outcomes in terms of speech, language and education .
- The critical age for commencing intervention may be as early as 6 months.
- Parents may quickly recognise a baby as having severe or profound hearing loss, but moderate hearing loss or high-frequency hearing loss may go unnoticed for several years unless formally tested.
Screening tests for hearing loss
The coverage and newborn hearing screening uptake across England is around 98%. Although the vast majority of babies pass the test, around 2% of babies are referred to audiology services for further assessment.
Neonatal hearing screening tests
Automated otoacoustic emissions (AOAE) test
- The AOAE test measures the integrity of the inner ear.
- It works on the following principle:
- In the healthy cochlea, vibration of the hair cells in response to noise generates acoustic energy, known as otoacoustic emissions. A probe is placed in the ear canal and generates wide-band clicks. Acoustic energy produced in response to the clicks is detected by a microphone within the probe.
- AOAE screeners display the results of the test as either pass or refer, requiring no test interpretation by staff.
- The test takes a few minutes.
Automated auditory brainstem responses (AABR) test
- The AABR test 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 otoacoustic emissions (because the cochlea is normal).
- The stimulus (either clicks or tones) is presented using earphones or an ear canal probe, and the electrophysiological response from the brainstem is detected by scalp electrodes. Automated devices allow screening to be performed by non-specialists.
- This test takes 15 minutes.
- Both tests require a quiet baby and a quiet environment.
- Debris in the canal or middle ear fluid can affect the tests (including amniotic fluid in the ear canal following birth).
- Only the AABR test will detect auditory neuropathy (where the cochlea is normal).
- Neither test will detect central hearing impairment (where hearing loss is secondary to dysfunction of the pathways from brainstem to auditory cortex).
Current screening protocols in the United Kingdom
Well baby protocol:
- For babies who had no requirement for special care (or <48 hours in special care).
- Uses the AOAE test. Babies not passing this test are given the AABR test.
Neonatal intensive care/special care baby unit protocol:
- Uses both AOAE and AABR tests. The latter can detect auditory neuropathy, which is more common in special care babies.
- If these tests are not 'passed', babies are referred for audiological assessment.
- If there are risk factors requiring surveillance, refer for continued audiological assessment.
School entry hearing test
- Currently, this is performed in most areas of the UK.
- The test used is the 'pure tone sweep test'.
- Following the introduction of newborn screening, most cases of hearing impairment will be identified before school entry, however there will be some cases that were missed or have developed after the test.
- The Child Health Subgroup of the UK NSC recommended that screening for hearing loss in school age children should continue while further research is being undertaken.
- A recent study found that the school entry hearing test may have a small but important role to play in identification of childhood hearing impairment.
Further hearing tests in children
Various tests can be performed by the audiological service, depending on the age of the child and level of co-operation. For example, in the 'toy test' the child points to toys named by the tester in a low voice. Pure tone audiometry is used with older children who can co-operate.
Visual reinforcement audiometry (VRE) is now used in preference to distraction testing. The test is a behavioural test which can be carried out with young children between the developmental ages of 6 months and 3 years.
Awareness and referral during childhood
Even if the hearing screening tests have been 'passed', parents and carers should continue to be vigilant for signs of hearing loss, because:
- Hearing loss may develop later.
- Some children may have missed out on screening programmes - eg, new immigrants.
- Some hearing loss may be missed on screening.
- High-frequency loss may not be obvious to family and carers, but will nevertheless impair understanding of speech.
Symptoms of hearing loss
The child may be:
- Inattentive, not reacting when called
- Talking too loudly, listening to TV at high volume
- Mispronouncing words
- Unsettled at school
- Tired, grumpy or overactive
- Demonstrating difficult or withdrawn behaviour
Who should be referred for audiology assessment?
- Those children who did not pass the screening test.
- Those children who missed their screening test.
- Babies with the following risk factors need to be referred for targeted follow-up, even if they pass the screening tests:
- High risk of middle ear problems: syndromes associated with hearing loss (eg, Down's syndrome, Turner syndrome), cleft palate, other craniofacial abnormalities (eg, atresia/microtia of the ear canal; chromosomal or syndromic conditions, branchial arch and cervical spine anomalies).
- Congenital infection due to toxoplasmosis, rubella or cytomegalovirus.
- Had special care for >48 hours, and no clear response to AOAE in both ears despite clear response on AABR.
- Babies with the following risk factors need to be referred immediately to Audiology for assessment:
- Any parental or professional concern.
- Confirmed or strongly suspected bacterial meningitis, or meningococcal septicaemia.
- Temporal bone fracture.
- Severe unconjugated hyperbilirubinaemia.
- Children with delayed speech and language may also require referral.
- After treatment with ototoxic drugs (eg, aminoglycosides), they should be referred only at the discretion of a paediatrician. If a baby is suspected or known to have the A155G mitochondrial mutation and received aminoglycosides then they should be referred for immediate follow-up.
Note: although family history of hearing loss has been removed as a risk factor requiring targeted follow-up, any parents who express concerns about hearing despite the screen should always be referred to Audiology.
Further reading & references
- Pimperton H, Kennedy CR; The impact of early identification of permanent childhood hearing impairment on speech and language outcomes. Arch Dis Child. 2012 Jul;97(7):648-53. doi: 10.1136/archdischild-2011-301501. Epub 2012 May 1.
- Guidance for Auditory Brainstem Response testing in babies, Version 2.1; NHS Newborn Hearing Screening Programme (March 2013)
- Bamford J, Fortnum H, Bristow K, et al; Current practice, accuracy, effectiveness and cost-effectiveness of the school entry hearing screen. Health Technol Assess. 2007 Aug;11(32):1-168, iii-iv.
- Bristow K, Fortnum H, Fonseca S, et al; United Kingdom school-entry hearing screening: current practice. Arch Dis Child. 2008 Mar;93(3):232-5. Epub 2007 Nov 26.
- Guidelines for surveillance and audiological referral of infants & children following the newborn hearing screen, Version 5.1; NHS Newborn Hearing Screening Programme (June 2012)
- Wood SA, Davis AC, Sutton GJ; Effectiveness of targeted surveillance to identify moderate to profound permanent childhood hearing impairment in babies with risk factors who pass newborn screening. Int J Audiol. 2013 Mar 11.
|Original Author: Dr Naomi Hartree||Current Version: Dr Louise Newson||Peer Reviewer: Dr Helen Huins|
|Last Checked: 13/05/2013||Document ID: 2238 Version: 24||© EMIS|
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