Universal Neonatal Hearing Screening

Universal Neonatal Hearing Screening

Scottish Implementation

April 2001

1.Introduction

1.1Permanent congenital hearing impairment (PCHI) is a condition affecting about 1.1 per thousand live births. On the basis of some 57,000 live births per annum, one may anticipate some 60-65new cases of PCHI per annum in Scotland. It is more common than other conditions routinely screened for at birth such as congenital hypothyroidism (1 in 25,000) and Phenylketonuria (1 in 14,000). Universal neonatal hearing screening (UNHS) is more health-effective in the detection of hearing impairment in children than present screening methods, the infant distraction test (IDT) and targeted neonatal hearing screening. Evidence-based health technology assessment has demonstrated conclusively that the detection and treatment of permanent congenital hearing impairment (PCHI) before 6months of age results in substantially greater speech acquisition with consequent benefits that are likely to be life-long in duration and include social and psychological well-being, educational achievement and employment prospects. UNHS offers detection of PCHI at or shortly after birth with a greater degree of accuracy and completeness of population coverage than present screening methods and at an overall cost per case of PCHI detected less, or at worst equal to present funding levels.

Background

1.2In December 1999 the Children’s Sub-Group of the National Screening Committee (NSC) recommended the introduction of UNHS. Although the recommendation was based on robust evidence from international and UK studies, the NSC recognised that there were issues and concerns surrounding the feasibility and management of the service which merited exploration through piloting.

1.3In July 2000 the Department of Health announced its intention to pilot Universal Neonatal Hearing (UNHS) to replace the Infant Distraction Test (IDT). At this time, the Scottish Executive Health Department asked National Services Division (NSD) to conduct a review of the resource implications associated with implementing such a programme in Scotland and options for its introduction. Specific issues to be taken into account were to include:

• the high number of initial false positive tests anticipated

• the programme’s ability to cope with early discharge of babies from hospital

• the lack of national validation criteria, quality standards, performance management and monitoring criteria.

• the ability of the paediatric audiology service and deaf educators to cope with the service implications.

Approach to Task

1.4The Medical Director and the Nursing and Quality Adviser of NSD have undertaken the review with assistance from the screening team at NSD and Medical Officers at SEHD. We have sought to determine existing practice in Scotland and the resources that are available at present with a view to considering what additional resources will be needed for UNHS to be successfully implemented in Scotland.

1.5Visits have been made to several audiology departments around Scotland to gather information on current practice and to gauge professional opinion. A questionnaire was sent to Directors of PublicHealth and copied to Commissioners of Child Health Services in Health Boards and Medical Directors of Trusts at the end of January2001. The information obtained from responses has been of assistance in the review process and is summarised in section 4.

1.6From these enquiries it became apparent that the greatest concerns regarding the impact of UNHS implementation, in terms of resources, were not in relation to the screening process itself but to the potential burden on professional audiology staff who would be seeing children at an earlier age and, perhaps, in greater numbers than at present. There was concern that this could have implications for the numbers, recruitment, retention and training of the professional groups concerned (audiologists and audiological scientists). For this reason, it was considered necessary to explore with providers of higher education, Scotland’s teaching and training capability in these areas.

2.Current Situation in England

2.1Invitations were issued to Health Authorities in October 2000 to apply to become a pilot site. A selection panel with members chosen from professional and voluntary bodies was established and selected 20sites to participate in the pilot. It is a requirement that pilot sites use the oto-acoustic emission (OAE) test as the primary screening test.

2.2The 20 sites selected should afford a cross section in terms of demographics and present position with regard to hearing screening. The pilots will commence in four stages. The first stage is scheduled to begin in April 2001, with the other cohorts coming on stream in July, September and November this year.

2.3Central funding is available for equipment, information technology, training and project management. Funding is not available for the provision of service.

2.4The Institute for Hearing Research (IHR) at the Medical Research Council are leading project management and implementation work and the National Deaf Children’s Society are developing information leaflets for parents for use and evaluation at the pilot sites.

2.5A limited tendering exercise has been undertaken for the evaluation of the project. This has recently been awarded to Professor JohnBamford of ManchesterUniversity.

3.OAE versus AABR as the screening test

3.1Although the English pilot sites are required to use OAE as the primary screening test, one Scottish audiology service (serving Highland and the Western Isles) is of the clear view that AABR represents a better option, at least in the circumstances of their service. This service has secured funding under the Remote and Rural Areas Resource Initiative (RARARI) to pilot UNHS using AABR as the primary screening test. This initiative is under way. Consideration, therefore needs to be given to the relative resource implications and benefits of these twoapproaches to primary screening.

a.Oto-acoustic Emissions (OAE)

OAE testing is a non-invasive test, which tests the function of the hearing receptor organ, or cochlea, but does not test the functionality of the connections between the cochlea and the hearing centres in the brainstem. The test can be performed at the bedside and a pass or fail response is recorded. OAE has a sensitivity (ability to correctly identify babies who truly have hearing deficit) of 100%. The specificity (ability to correctly identify babies with normal hearing) of OAE is, however, reported as being 82-87%. The false positive rate for OAE is particularly high in babies less than 48hours old when the ear canals may be blocked with material left over from birth.

Babies who “fail” the screening test require to undergo further investigation with a consequent impact on specialised resources as well as the potential for distress and worry for parents For every 1000babies tested, 130to 180will require further testing out of which one will be found to be suffering from PCHI.

Nevertheless, OAE is, for the present, regarded by the National Screening Committee as the established primary screening test and is mandatory for centres participating in the English pilot project.

1. Automated Auditory Brainstem Response (AABR)

Automated Auditory Brainstem Response is an elaboration of a conventional (ABR) system. Both systems rely on careful application of electrodes and earphones. This makes for a more complex process than oto-acoustic emission testing but information on the whole auditory system is obtained including the functionality of connections to the hearing centres in the brainstem. Ambient noise (electrical and acoustic), physiological noise and movement can affect the response so that more care needs to be taken in carrying out the test than is the case with OAE.

The primary difference between automated ABR and conventional ABR is in the interpretation of the response. Conventional ABR provides objective information but interpreting the output requires professional expertise and judgement on the part of an audiology clinician. Automated ABRs depend on an internal algorithm that interprets the incoming signal and determines if the response is a 'pass' or a 'fail' by statistical techniques. AABR testing can be performed with portable equipment. This equipment has not been widely used in the United Kingdom to date but is claimed by its proponents to be the test of choice in 80% of USA hospitals offering UNHS. The sensitivity and specificity of the AABR test are claimed by commercial manufacturers of AABR machines to be 99.96% and 98.7 respectively although it is not wholly clear what they are using as their proxy for the true hearing status of subjects examined. In contrast, the National Screening Committee quote sensitivity and specificity rates of 89% and 82-87% respectively for conventional ABR but do not address the role of AABR as a screening tool at all.

3.2Both tests are safe, simple and inexpensive although AABR has higher start-up costs because of the higher capital cost of the equipment required. By contrast, OAE may pose a greater burden on skilled staff who carry out confirmatory diagnostic testing if it turns out to be the case that the technique has a significantly higher specificity than AABR and requires second level screening by ABR and formal confirmatory testing, both being performed by skilled professionally trained staff.

3.3In any event, Scotland has an established UNHS pilot service based on AABR covering Highland and the Western Isles. Whether or not the funding of this programme is transferred from RARARI to a UNHS masthead, it would seem sensible to ensure that the experiences gained in this pilot, currently funded to run for 3years, should be included in the overall evaluation of an initial phase of UNHS introduction in Scotland. It is all the more important that this should be encouraged in the light of the fact that the English pilot does not afford such an opportunity.

4.Survey of Health Board-based Children’s Hearing Services

4.1A questionnaire – a copy of which is attached as Annex 1 - modified from one used as part of the information gathering exercise undertaken in England to identify the state of preparedness of Health Authorities for the introduction of UNHS, was circulated to Directors of PublicHealth in the 15Scottish Boards. It was recognised that the Island Boards receive the greater part of their specialist children’s hearing services from mainland Boards and it was not anticipated that the former would submit responses. Of the mainland Boards, 10submitted consolidated responses and one (Argyll & Clyde HB) submitted 3responses from discrete service elements within their Board area.

The responses are summarised in a set of tables at Annex 2.

4.2Two clear messages emerge from these analyses. Firstly, there are wide variations in the way that services are configured across Scotland; secondly, there is strong evidence of care and thought in the arrangements for the delivery of services and co-ordination with other agencies in most areas described.

4.3Targeted neonatal hearing screening is reported in 7Boards although the coverage of births is patchy. For example, in GreaterGlasgow some maternity hospitals but not all have instituted targeted neonatal screening.

4.4Should a centrally co-ordinated UNHS programme be instituted, there will be a need for a substantial measure of harmonisation of the arrangements that link such a programme to other parts of NHSScotland and to other agencies. This would take the form of agreed common policies, protocols and standards.

5.Workload

Needs Assessment

5.1There were 57,000 live births in Scotland in 1998. This was the lowest number recorded since civil registration commenced in 1855 and represented a drop of 11,500 annual births since 1980. Unpublished figures indicate that the number of births fell further in 1999 and 2000. For the purposes of planning, the number of live births to be screened is taken to be 57,000 per annum, distributed as per the distribution by Health Board-based service in 1998. This may be on the high side in the light of recent figures. Similarly, the sensitivity and specificity of OAE testing are taken to be 100% and 82-87% respectively.

5.2Table 1 shows the impact of introducing OAE-based UNHS, by individual Health Board-based service in terms screening and confirmatory tests.

Table 1

5.3The population to be screened is represented by the annual number of live births and this is assumed, for the purposes of planning, to remain constant irrespective of whether or when UNHS is introduced.

Impact of UNHS on current service

5.4Screening currently takes the form of the infant distraction test, carried out by Health Visitors in the community as part of an overall child surveillance programme, augmented in most areas by targeted neonatal hearing screening carried out by audiology staff for the most part. The impact of transferring this work to a new cadre of semi-skilled screeners will be to:

1. release a Health Visitor resource which, although valuable to the NHS as a whole, will have little utility in terms of neonatal hearing;

1. release an Audiologist resource which will be available to service any additional burden on audiology services consequent on the introduction of UNHS.

5.5To be fully effective, confirmatory testing should be carried out at about 44 weeks gestation (4 weeks of age in a full term birth; somewhat later in premature births). For this reason, it is important that waiting times do not develop for confirmatory testing. It is a prerequisite of establishing UNHS, therefore, that there is a clear path from screening to confirmatory testing and that confirmatory testing is fully resourced by Health Boards and Trusts from the outset.

5.6Targeted neonatal hearing screening has been shown to pick up some 50%of PCHI so that, in areas where targeted screening takes place, the additional cases ascertained in the neonatal period by UNHS are likely to double the burden of confirmatory testing in this stage.

5.7The effects of the introduction of UNHS are as follows:

1. a cohort of children who would have failed targeted neonatal hearing screening will be ascertained by UNHS within the same timeframe as currently applies; this is likely to represent around 50% of all neonatal ascertainments (ie around 7-8% of births) becoming candidates for confirmatory testing.

1. a further cohort of children of about the same size (ie 7-8% of births), who would have been ascertained by IDT at age 6+ months will be ascertained in infancy.

1. Over the first 6 months or so of a new UNHS programme, there will continue to be referrals from IDT testing of births in the 6months prior to the introduction of the programme. The number of such referrals will vary depending on the local “fail” rate of IDT. This can vary in different services between 10 and 20% of children tested. On this basis, one would expect a continuation of referrals from IDT at around 10-20% of monthly births each month for 6or so months.

6.Staffing Implications

Screening

6.1 The screening testsare not complex and can be carried out by staff who have no special knowledge or skills in hearing science but who are good with babies and can assimilate the basic training required. It is not critical whether they have other clinical skills or not. The OAE screening test is more time consuming than the AABR test and can take up to 40 minutes per child, requiring the baby to be settled or asleep during the test. AABR is quicker and less demanding of the child’s level of activity. The level of resource and cost attaching to screening will depend on the staff group recruited to the task in specific settings. This may range from midwives or other professional care workers to lay staff recruited and trained specifically for the task depending on local circumstances. Phlebotomists come to mind by way of an example of the latter approach. This is more likely to be implemented in large maternity units where the number of births would justify the necessary pool of 2-3 trained individuals. While the objective should be to carry out screening in hospital (i.e. prior to discharge) wherever practicable, there will need to be failsafe arrangements to pick up the minority of cases where this is not achieved. This could be achieved through the community midwife service.

Confirmatory testing

6.2Confirmatory testing is a skilled task, requiring the personal involvement of a senior medical technical officer (audiologist) or clinical scientist. The extent to which the introduction of universal screening will pose temporary or permanent additional burdens on this staff group depends on the number of babies who “fail” the screening test(s) and the time taken to carry out diagnostic testing in each case. It is clear that the introduction of UNHS in infancy will at the very least impose strains in the system consequent on the fact that, for a period of time, two cohorts of children will be coming through for confirmatory testing, those screened under the new programme and those tested by the current distraction test at 6-9months. This situation will prevail during the period of rollout of UNHS nationally and for about 6-12months after its completion. The impact in any particular Health Board area or unit of hearing services will be of the order of 6–12 months.

Follow-up

6.3Once a child has beenconfirmed as having a hearing loss they willrequire ongoing care from their local paediatric audiology department from the age of about three months when they can be fitted with hearing aids. If the child has a profound hearing loss they may be a suitable candidate for cochlear implantation. This operation is ideally performed before the child is five years of age.

Support from Rehabilitation Specialists

6.4Depending on the severity of the hearing loss the child may require the support of rehabilitation specialists (e.g. teacher of the deaf, speech & language therapist). The child’s level of hearing impairment will also help determine their educational requirements, which may be in a main stream school with or without assistance from a teacher of the deaf, or in a school for the deaf.

Training

6.5Staff with no previous audiological training can carry out initial screening. They need a familiarity with the equipment used which can be acquired through on the job training and they require to comfortable handling small babies. Experience and training in speaking to parents is essential.

6.6Confirmation testing is a skilled task and requires the skills of a Clinical Scientist with Physiological Measurement experience or an Audiologist trained in physiological measurement.