6. Childhood hearing screening after the neonatal period (preschool/school screening)
Chapter editors: Inger Uhlén, Andrea Bussé
a. Context and introduction
Childhood hearing screening after the neonatal period aims to detect hearing impairment (HI) that was not identified at birth or has been later acquired. In countries with NHS in place, the prevalence of HI in school age children is about twice as high as compared to newborns, though estimates vary depending on thresholds used1 2 3. The increase of HI with age is explained by delayed onset HI, progression from a mild HI or auditory neuropathy not detected via NHS or acquired HI from infections, ototoxic medication and trauma4.
HI may present itself any time after NHS, most often as a delayed speech or other communication disorders. Hearing should always be investigated when there is a delay in speech and language development and in children with recurrent ear infections. HI of mild to moderate degree may however go unnoticed for many years and its consequences on a child’s behaviour may be misinterpreted as a behavioural or intellectual disorder.
Unlike NHS, the long-term benefits of childhood hearing screening (CHS) after the neonatal period have not yet been established, particularly in the context of a hearing healthcare plan that includes NHS. In Europe, CHS is not as widespread as NHS. Many existing CHS programmes began in the 1950s to 1970s prior to implementation of NHS. In recent years, a few additional countries have adopted a CHS programme while other CHS programmes have been terminated. There is a gap in the literature in the cost-effectiveness of CHS, with only one recent study performed on CHS in the framework of the United Kingdom National Health Service5. This study concluded that CHS does not offer good value for money, based on the number of new cases detected; however, the authors themselves noted limitations to the study.
The role of CHS may be different in regions where NHS has not been implemented. In these regions, children with HI may not have been diagnosed until four or five years of age, when the negative effects on language, learning and social interaction are observed. CHS should not be an alternative to NHS, because moderate or severe congenital hearing loss diagnosed at four or five years of age can never fully be rehabilitated. It is important to note that CHS pick up children with mild hearing loss much more often than those with greater hearing loss in regions where NHS is in place.
Hearing tests for children
Hearing may be assessed with various methods according to the age and developmental level of the child. These methods are objective, observational and behavioural. Objective methods are typically OAE and ABR used for NHS, where a passive response to sound can be recorded from the child. These methods can be applied also in older children and under anaesthesia. Infants from 3 months to about 2 years of age are extremely difficult to test as they cannot take instructions and have a very short attention span. The test person may only observe the child’s reaction to sound which can be very hard. In the distraction test and visual reinforcement test (VRA), the child is conditioned to turn its head towards the direction of the sound. This method has been used for infant hearing screening at 7-8 months of age, a screening that has been abandoned after implementation of NHS. From 3-4 years of age the child can be trained to actively show when they hear a signal, for example by building blocks or pushing a button. This behavioural test method is most often used for pure tone audiometry (PTA), where tones are presented in headphones, at different frequencies and intensities. This is the preferred method for hearing screening in children from 3 years of age and up6 because of its high sensitivity and reliability7. There is also the so-called whisper test which requires no equipment, but is of limited value for CHS due to its poor reliability and sensitivity8.
b. Pre-implementation considerations and preparations
The implementation of a childhood hearing screening needs good planning and detailed preparation to achieve a sustainable and cost-effective programme. Information is essential, including all stakeholders and others involved in the planning and implementation. See the checklist below for what should be taken into consideration.
- Whether the proposed programme is local, regional or national
- How stakeholders will be informed about the proposed programme; such as child healthcare providers, school healthcare, school officials, ENT-centres/clinics, hearing services
- How parents will be informed and consent gained for their child to be tested
- Who/what authority will be in charge of the programme – for implementation and further provision?
- How the programme will be financed – implementation and for sustainability.
- Will screening be free of charge or offered to families at a cost?
- Where are the children available? In preschool, school, healthcare office or other settings.
- Is there one public school organisation or several providers? Boarding schools.
- How large is the population regarding the target age group?
- Where and at what ages are there established health check-ups?
- Is there a routine check-up where hearing screening can be included?
- What requirement exist for consent for medical procedures
- How will the programme be administered, conducted and reported?
- Is IT-support available?
- How will screening results be collected and used?
- How screening results will be informed to parents and caregivers?
- Who will do the screening and how will they be trained?
- The choice of test equipment and protocols to use.
- What routes exists for raising awareness of hearing screening and informing parents about the screening programme?
- What diagnostic and intervention services are available for children referred from the screening programme?
- How are further diagnostics and intervention financed? Is there equity so that every child in need will receive intervention irrespective of family economy?
c. Planning a CHS programme
i. Target population
The target population defines who is eligible for CHS. Factors that are included in eligibility include jurisdiction, age, and universal vs. selective.
- Jurisdiction: The target population must be defined, and responsible authorities appointed. CHS must be connected to an institution where a majority of children can be reached. CHS can be performed in school or in combination with other healthcare appointments to achieve high attendance (see chapter 4b). Furthermore, the healthcare and education boundaries may need clarification to identify in which regions or school systems a screening programme is implemented, as authorities across these organisations may not coincide. In HIC, with well-established healthcare plans for small children and healthcare for schools, the responsibility for screening programmes is often well defined. In countries where healthcare centres are few and regular check-ups are not available for all, setting up CHS will become very difficult.
- Age of child: CHS may be performed at one or more occasions during childhood. In many countries, CHS is performed at age four and in most cases, screening is part of a general health check-up9. Screening may also be performed at school start, since school is mandatory, and attendance is expected to be high. However, this may be late since school start varies between countries from 4 to 6 years of age.
- In addition, children should be old enough to reliably perform a behavioural test. In most cases, behavioural audiometry using play (play audiometry) can be performed by age three (see section v). Screening too early may cause inconclusive test results with unnecessary referrals as a consequence.
- Hearing screening should target all children, irrespectively of age, who have not previously been offered screening or when a pass result cannot be confirmed, for example children immigrating from countries without screening programmes.
- Universal vs. selective: most CHS opt for implementing a universal programme, in which all children are eligible for screening. It may be important to identify the established local protocols for surveillance of delayed-onset hearing loss among children who pass NHS, prior to defining the target population for CHS. For example, are children with risk factors for hearing loss monitored after NHS and what are the already established checks for at-risk monitoring? It is important to note that childhood hearing loss also affects children without known risk factors.
- Children who are difficult to test: tests designed for typically developing children may not be suitable for children with multiple disabilities or syndromes that affect cognitive and intellectual development. Behavioural and objective test methods may be needed to assess hearing, performed by an experienced audiologist. Furthermore, these children may miss routine health check-ups due to intensive medical care. However, it is of utmost importance that these children have their hearing tested as part of other check-ups. In a child where a delayed or absent speech development may be part of the syndrome (for example Down syndrome), HI may go undetected. Guidelines for follow up should include hearing assessment.
ii. Target condition
Hearing screening is a health check-up, with the specific aim to target children with HI in need of intervention. Hearing thresholds in healthy children, tested at 0.5 – 4 kHz, are normally below 10 dB HL10. Screening at 20 dB will then give robust responses in most children. Higher frequencies (6-8 kHz) show more deviations. Middle ear effusion (OME) may cause a conductive HI of 25-45 dB. CHS programmes may be designed to target children with mild or moderate HI. Prior to a decision, an analysis of the local intervention practice may be warranted to assess the availability and equity of care across different types and degrees of HI. See Appendix 2 for hearing test protocol.
- Screening is typically performed at a fixed level of 20 or 25 dB, over selected frequencies from 250 to 4000 Hz (6000 Hz), depending on the age of the child and test location. Screening at 20-25 dB is recommended in children from 6 years of age, while 25-30 dB is accepted for younger children. Testing in a sound-treated room also allows lower screening levels.
- Referral criteria need to be defined, as the number of frequencies with a pass at the target screening level in one or both ears. Referral criteria will define whether the protocol will target mild, unilateral or moderate hearing impairment. Screening at 20-25 dB in both ears will target all HI, including mild and unilateral.
- Targeting mild HI (<40dB) may also include children with temporary HI due to OME. A retest after a couple of weeks may be necessary when the fluid in the middle ear has resolved and the hearing is normal. If not, the child should be referred to a diagnostic centre or ENT physician (see section Referral routines below).
- All children who do not pass CHS, have an inconclusive test result or are not able to perform the test must be referred for further investigation.
iii. Screening location
The three most common locations for CHS are at preschool, at school or at a child healthcare centre. The EUSCREEN survey revealed that in approximately half of the countries that have CHS programs, screening is performed in school and in the other half in a healthcare centre.
A careful look at the infrastructure around school and healthcare check-ups should be performed. At early ages CHS may be combined with regular health controls and vaccination programmes, while for school age children testing may be better performed in school. For the test to be effective and to ensure accurate referrals, it is important that children are well prepared by the screener so that they understand the nature of the test and feel confident about how to respond. All hearing tests require a quiet environment, a specific test device and a trained staff who can support the child to perform the test and evaluate the result. Please refer to chapter 4 for more information regarding general concepts and potential effects regarding selecting location (school versus child healthcare centre). In addition, the financing authority may also affect the decision on location.
Within the selected location, the test environment needs to be established. All test methods require a quiet room for screening, preferably a sound-treated test room, since background noise can significantly affect the results. The test environment is ideally quiet without distractions, so that the child can engage with the tester to perform the test. A small child also needs to find the test playful. The hearing test needs the child’s full involvement, or the results may be inconclusive.
- In a healthcare centre, hearing screening should be incorporated into the general healthcare programme.
- Hearing screening can be incorporated into an already-established check-up in order to ensure high levels of attendance. However, too many tests at the same appointment may exhaust the child. In this situation, requiring a separate appointment for hearing screening. Thus, hearing screening should be offered according to the needs of the population.
- In a school setting, hearing screening will be performed on certain age groups or all children in the school. In this situation, the day and time of screening can be selected. Screening should be coordinated with the teachers in the schools to ensure that as many children are in attendance as possible.
- Ensuring that parents have given appropriate consent.
iv. Screening personnel
Implementation of screening in child healthcare centres would imply that child healthcare workers (physicians, nurses, or nursing assistants) would need training and adequate ongoing practice. Healthcare workers should be performing screening regularly, several times per month to maintain proficiency. In contrast, in a school setting, one screener may perform all screening for the children in the school. This may be a school nurse, or a travelling nurse or audiologist.
Training to become a screener should include theoretical and practical parts. Basic knowledge about hearing, hearing impairment and intervention is essential. Basic knowledge is also required about the anatomy of the ear and ear canal, including common deviations such as clogging cerumen, discharge and atresia. Audiometry requires understanding sound levels in dB, hearing thresholds, the test device (audiometer) and the test procedure.
Testing children requires interest in and ability to communicate with a child and the accompanying caregiver. Practical training with an experienced screener for a period of days, is necessary to assure adequate ability to perform the test. Examination and repeated re-examination of theoretical and practical skills is necessary to assess good quality screening. A certificate for screening personnel may also enhance the status of hearing screening. If appropriate retraining should be done.
Regular follow up with feedback to screening personnel about the outcome of the screening program is important to confirm the importance of their work performance. The screener’s self-esteem, accuracy and reliability are key factors to maintain high quality.
v. Screening methods
A child of 4-6 years of age is in most cases able to respond to a signal by pushing a button or in some other way. Hearing thresholds may be assessed at four or more frequencies in one ear at a time, providing information of hearing in both ears. Pure tone audiometry is the most prevalent and recommended method for childhood hearing screening. Other test methods in use are also described below. Tympanometry and otoscopy are methods for examining the ear as part of a diagnostic investigation, and should only be used by a medically trained screener.
- Pure tone audiometry (PTA) is the recommended method for CHS. PTA requires calibrated equipment, trained personnel, and a behavioural response from the child. Hearing thresholds may be assessed, meaning the lowest sound stimuli that gives a response from the child. For screening purposes a fixed level that will be accepted as a pass is recommended. Screening level of 25 dB, or 20 dB for older children, is most commonly used since it refers to normal hearing. A child that does not meet these criteria will be referred for further diagnostics (for screening test protocol see Appendix 2).
- Advantages: can detect both unilateral and bilateral HI, can detect mild HI if desired, highly reliable.
- Disadvantages: does not distinguish between sensorineural or conductive hearing impairment, may be difficult for children with intellectual or cognitive disability.
- Play audiometry: Pure tone audiometry adapted for children 3-4 years of age, where a play component (for example to put an object in a box or put rings on a stick) replaces pushing a button when hearing a tone. Pure tones may also be replaced by warble tones that will easier catch the child’s attention. The number of frequencies tested may also be reduced. The child will need to do some activity to show that they can hear the tones. Some children will be able to respond by simply putting up their hand. Other children may need a game to stay engaged. The activity should be very simple, easy and not take too much time, for example placing an object in a bucket or sliding a ring onto a peg each time a tone is heard.
- Whisper test is a method that refers to the child’s ability to repeat words or numbers produced with a low voice in a quiet environment. Typically, both ears are tested separately, by turning the ear being tested towards the test person/screener and blocking the other ear with the hand or a headphone.
- Advantages: No expensive device is needed.
- Disadvantages: Significant issues are shown with regards to the reliability of the whisper test, which is also not ear specific. Results vary with the voice of the screener, sound environment and the childs ability to clearly repeat target words/numbers. This also requires normal hearing in the screening personnel. The whisper test is not a recommended screening method.
- Speech in noise or digits in noise test may be an alternative for testing via smartphones or laptops where stimulus levels cannot be calibrated. Hearing is assessed via an automatic adaptive procedure with a signal-to-noise ratio as outcome where the result will indicate need for further investigation.
- Advantages: Testing possible at remote places. No expensive test device needed.
- Disadvantages: Lack of evidence, especially in children. Headphones with specific requirements needed and a trained screener in place to support the child. Does not work in small children due to the level of language and cognitive development.
- Otoacoustic emissions (OAE), transient or distortion products, have recently been investigated as a possible tool for screening children this age. It is a sensitive method to detect mild and unilateral HI. In diagnostic evaluation it is a useful complement to PTA in children difficult to test. None of the countries surveyed perform otoacoustic emissions during childhood hearing screening.
- Advantages: does not depend on behavioural responses of the child, can detect unilateral and bilateral HI, highly reliable.
- Disadvantages: sensitive to fluid in the middle ear, difficult to achieve results in the low frequencies, sensitive to restlessness and noise, insertion of ear tips in the ear canal may require a medically trained screener.
- Tympanometry is a test that reveals the status of the middle ear and may be used in addition to above test methods to further explain the test result. In a CHS programme it may be used to diagnose or exclude OME and then either plan a rescreen or direct referral. Tympanometry may thus reduce the referral rate. However, it requires special expertise on the part of the screener, complicates the referral routine, and may lead to delay of necessary diagnostics and treatment of chronic middle ear pathology.
- Otoscopy with a handheld device may be used for inspection of the ear canal to ensure free passage to the eardrum. Otoscopy may, similar to tympanometry, explain a refer result due to a wax plug or infection. For diagnosis and treatment, a medical professional is required.
- Hearing test via smartphones and other ways of remote testing for screening purposes may be administered in certain areas. These tests are based on a signal-to-noise ratio that will indicate a need for further hearing investigation11 12. For screening purposes these methods also require a set standard of equipment and a screening staff in place. The possibilities with this method have to be further investigated.
Screening must be conducted in a reasonably quiet environment, with as few distractions as possible. Ambient noise (from ventilation, stairs, hall traffic, play areas, children moving about in the test room or screening personnel giving instructions) will make screening more difficult and could result in false positives. The screening room should also have at least a table, two chairs and an electrical outlet.
The minimum requirements for selection of a screening audiometer are:
- portability: it is important the audiometer can be moved between locations. It should be sturdy so that damage is not caused by packing and unpacking each day. This is even more important when the screening is performed in the schools, as the equipment will be brought with the screener each day
- tones: the audiometer should be able to produce pure-tone stimuli through headphones
- sound level: the audiometer should be able to test down to 20 dB HL
- calibration: the audiometer should be capable of being calibrated locally
Additional considerations when deciding on an audiometer
- battery-operated: if the environment will not have consistent electrical power supplied, then a battery-operated audiometer should be strongly considered.
- some audiometers contain additional features outside the minimum requirements (for example, bone condition, speech testing). These are typically more expensive and unnecessary for screening purposes.
The screening audiometer should be calibrated yearly to ensure that the correct stimuli and levels are being delivered.
It is recommended that the sound is delivered via headphones to each child to get ear-specific information. It is recommended that headphones are the over-the-ear style or alternatively in-the-ear style. Insert earphones (with foam tips that slide into the ear canal) are another possibility, but these are often not accepted by young children and more expensive as the foam tip is thrown away after each child. Ensure that the earphones selected are appropriately sized to fit young children.
A device for tympanometry or otoscopy is not standard equipment for a screening programme. These methods are part of clinical investigation and require a medically trained screener.
Forms and documentation
The following forms and documents should be prepared (more information on the contents of these documents is available in section f below and Appendix 2):
- information leaflets to be provided to parents prior to hearing screening
- consent form to be collected from the parents if screening is performed in school, that is, without the parents present. The local policy regarding informed consent should be followed. Information needs to be available to the screener on how to contact the parents in cases where the child has failed hearing screening. Consent may also be collected to allow sharing information to healthcare providers in the case of a failed hearing test
- test sheet to document the individual results of the hearing screening
- referral letters to parents/caregivers and healthcare providers
It is very important that the equipment is clean and disinfected between each child, to prevent infections from spreading from child to child. Sanitary disinfection wipes or sanitary disinfection solution with disposable clothes should be ready prior to testing. All equipment should be cleaned regularly, and the headphones should be wiped clean after each test.
A child that does not pass the CHS should undergo audiological examination to determine the severity and type of the HI. A sensorineural HI may be treated with amplification, but many of the referred children will suffer from middle ear disease, which necessitates ENT examination. Ideally, the child should be referred to an institution that offers both audiology and ENT services. Alternatively, the child is referred for audiometry, to be followed by ENT consultation if that is indicated. Local existing practice should be considered to determine the referral path. It should be clear who is responsible for making the follow-up appointment.
- Parents should be made immediately aware of the results and the recommendations for referral.
- The recommended procedure is that the screener directly schedules an appointment with a qualified audiology clinic. The follow-up clinic (audiology or ENT) should be notified of the results of the hearing screening (if legally possible).
- If the audiology or ENT clinic is responsible for making the appointment, the information regarding the child’s screening test result in addition to the contact information of the parent/caregiver should be provided to the clinic (note that this is subject to local laws pertaining to the sharing of information – see Chapter 4 for more information on legal considerations).
- If the parents are responsible for making the follow-up appointment, it must be very clear how and where the follow-up appointment should be made. Contact information should be provided for the clinic where the appointment should be made. Information should be provided both written and verbally.
- Additional information should be provided to the parents why it is important that they follow up after a hearing screening referral. A phone call may be scheduled after a set duration (2-3 weeks later, for example), to ensure and document that the parents did make the follow-up appointment.
- The outcome of the hearing test should be documented in the child’s individual health record (if available) and should also be communicated to the primary care practitioner.
i. Information for parents
Information about the screening programme is important, and can be provided with information leaflets and/or by personnel at the healthcare centres and schools. This subject is covered in chapter 10 and specific advice on information leaflets can be found in Appendix 3.
ii. Public awareness
Communicating the arguments for CHS to the government, policy makers, healthcare providers, educational settings and citizens (parents) is a key factor in the early planning. The more aware the public is about the importance of screening, the higher chance of sustaining an effective screening programme.
iii. Information for care providers
Information about the hearing screening programme must include all stakeholders who will be responsible for or involved in healthcare and children’s early development. Information can be disseminated through leaflets, presentations at professional society meetings, educational programmes and healthcare board meetings.
iv. Monitoring and reporting
As with newborn hearing screening, quality assurance and the systematic monitoring of programme performance and outcome are essential for a childhood screening programme. All elements of the pathway should be monitored to ensure the programme meets its aims and screeners should be well trained and regularly assessed to ensure their ongoing competency.
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