Introducing universal newborn hearing screening in Denmark: Preliminary results from the city of Copenhagen

 

KONRAD S. KONRADSSON¹ , ERIK KJAERBOEL¹ & KLAUS BOERCH ²

¹ Department of Audiology, H:S Bispebjerg Hospital,

² Department of Paediatrics, H:S Hvidovre Hospital, Copenhagen University Hospital, Denmark

Introduction

          In the year 2004 funding was made available by the Government of Denmark (2005 population: 5.4 million) to introduce universal newborn hearing screening (UNHS). This funding is, however, limited to a two-year project with the results of the screening to be analysed at the end of the project period. In 2005 there were 64,189 live births in Denmark and the sum projected for the screening is equivalent to 31€ for each newborn baby during the two-year period. The single initial sum of 1.3 million €, for screening equipment and other initial investments, was also included in the funding.

In August 2004, The National Board of Health published Guidelines for the Universal Newborn Hearing Screening in Denmark (1).
There were three main goals to be met:

There are 16 more or less autonomous counties in Denmark that provide the health services. In the guidelines, the counties are given several choices including a choice between the use of automated otoacoustic emissions (OAE) testing or auditory brainstem responses (ABR) as the first step of two for the primary screening of babies from the well baby nurseries (WBN). Automated ABR recording is recommended for the second stage.
The infants from the neonatal intensive care unit (NICU) (more than 48 h stay) are to be tested with both methods _ automated OAE and ABR – just before discharge from hospital.
The infants lacking clear responses are referred for re-screening using ABR at an audiological department.
Infants with head and neck malformations and/or chromosomal anomalies are not to be included in the screening process, but referred directly to an audiological department.
The provision of newborn hearing screening is mandatory and universal in Denmark, i.e. all parents are informed of the screening and are advised to have their babies screened, but the parents are free to decline the offer. The screening, as well as re-screening and the later ascertainment and rehabilitation procedure, is completely free of charge.
The present study presents the results from two Copenhagen hospitals – the Hvidovre and Frederiksberg hospitals after 12 months of screening.

Method

        In the Copenhagen city area (2005 population: 0.6 million) there are three hospitals with maternity clinics:

There are Neonatal Intensive Care Unit (NICU) clinics at the Hvidovre Hospital and Rigshospitalet.

At the Hvidovre Hospital and Frederiksberg Hospital, the hearing screening is conducted in association with metabolic screening tests at the age of four to ten days for infants from the WBN. This means that the parents take their infants home from the WBN and bring them back to the hospital a few days later for the screening. The screening method uses automatic recording and evaluation of transiently evoked otoacoustic emissions (aTEOAE), measured in both ears. An evaluation - clear response (CR) or no clear response (NCR) – of the recorded response is automatically produced by the instrument’s algorithm. The recording is repeated the same day or the next weekday if there are technical or practical problems or NCR for either or both ears is obtained at the first recording. When there are clear aTEOAE responses the parents are informed that the probability of hearing impairment (HI) is low and the infant is then discharged from the screening programme.
Infants from the NICU clinic (>48 h stay) are tested with automatic recording of TEOAE and ABR before leaving Hvidovre Hospital. CRs from both recordings and from both ears are required.
After the screening, if there is NCR, the infant is to be referred for re-screening at Bispebjerg Hospital. The re-screening is located separately from the audiological department so as not to mix parents and infants coming for re-screening and children with hearing impairment. The re-screening consists of new recordings of aTEOAE and aABR.
If there are clear aTEOAE and aABR (35) responses from both ears the parents are informed that the tests are normal and that there is no suspicion of hearing impairment. They are also asked to remain vigilant regarding symptoms of hearing impairment and to seek audiological advice if there is later any doubt regarding hearing acuity.
If there is no clear aTEOAE response, but a clear aABR (35) response the parents are informed that the probability of hearing impairment is low, but the infant’s hearing should be checked after six to eight months. If there is no CR from either recording (aTEOAE and aABR 35), in either or both ears, the infant is rapidly referred to the Department of Audiology at the same hospital for diagnostic evaluation.
The equipment used for the screening and re-screening is the GN Otometrics Accuscreen (2), which is capable of automated TEOAE and ABR recordings and response evaluation. The instruments are calibrated, maintained and used according to the manufacturer’s specifications.

Results

The coverage of the hearing screening during the first year of screening (February to December 2005) was 98.5% of all children (n=6594) born at the Hvidovre Hospital and Frederiksberg Hospital (see Table I of the original article). The coverage for the NICU infants (n=227) is somewhat lower or 86.8% in the period. Similar data from Rigshospitalet are not available.
In 96.1% of cases there was a clear response from both ears in the first screening and the rate of referred infants for re-screening after one or two screening attempts (aTEOAE) was lower than expected (1.4% of the total - Table II).
In the first full 12-month period (February 2005 to February 2006) 124 infants were referred to Bispebjerg Hospital for re-screening. Two children were referred from Rigshospitalet, and the remaining 122 from Frederiksberg Hospital and Hvidovre Hospital. Of this group, three children (2.4%) did not attend and were lost to follow-up.
The great majority of the infants were screened when they were brought back to the hospital at the age of four to 10 days for metabolic screening tests (see Figure 1 of the original article).
The median age of the WBN infants when referred for re-screening was 10 days (range 4-58 days). The re-screening was completed in another five days (range 0-28 days). For six of the 95 referred WBN infants the total screening period exceeded 30 days (range 32-59 days).
The results of the re-screening as well as ascertainment at Bispebjerg Hospital are shown in Table III. The number of infants with no clear TEOAE response from one or both ears, but with clear responses for aABR (35) in both ears is relatively high, or 19% of the total.
By February 2006, 12 infants have been diagnosed with bilateral and four infants with unilateral hearing impairment. The results from diagnostic ABR thresholds (2 and 4 kHz tone bursts) indicate that, of this group of 12 infants with bilateral hearing impairment, there is one infant with mild, five with moderate, two with severe and four infants with profound hearing impairment.

Discussion

In many screening programmes the relatively high referral rate after OAE screening soon after birth is considered to be a problem, which, in many programmes, is addressed by introducing a second stage aABR screen. In the present programme only 1.5% of the infants are referred for re-screening after one or two aTEOAE screening recordings. This relatively low rate limits the need for implementing aABR as a part of the primary screening process for the sole purpose of reducing the referral rate. The low referral rate also indicates that screening the infants when they are four to 10 days old (Figure 1) is a favourable period for the screening procedure.
Of the 124 infants referred after the primary screening, three (2.4%) failed to show up for the re-screening and were lost to follow-up. Two of the infants lost to follow- up were NICU babies and one was from the well baby nursery. The relatively high follow-up rate (97.6%) indicates definite parental interest in the screening process and an understanding of the importance of early detection of permanent hearing impairment.
The relatively low yield from the NICU infants (two out of 14 hearing impaired infants) can partly be explained because the NICU clinic at Hvidovre Hospital is relatively small and there is a lower coverage (86.8%) among the NICU infants compared to the WBN infants (98.8%). Two of the three children lost to follow-up were from the NICU.
The results of this study highlight the importance of giving proper information to hospital personnel and parents regarding the value of earliest possible detection of permanent hearing impairment. This is especially important for the NICU infants given the much greater risk for hearing impairment among these infants. The results also underline the importance of achieving the highest possible coverage, to adhere to the screening protocol and to secure a thorough follow-up for all newborn children.

References
1. The National Board of Health’s Guidelines of August 12 for Neonatal Hearing Screening [Danish]. Available on the Internet May 1st 2006 http://www.sst.dk/publ/Publ2004/Retningslinier_neonatal_hoerescreening.pdf
2. Accuscreen product specification. Available on the Internet, May 1 2006. http://www.gnotometrics.com/ha_infscreen_accutecspec.pdf

                                                                   (Full article: Audiological Medicine. 2007; 5: 176-181)

 

Konrad S. Konradsson, MD, PhD, is the Department Head of Audiology-Auditory Implants at the University Hospital in Uppsala, Sweden. Previously, he was Head of the Department of Audiology at Copenhagen University Hospital in Denmark (2003-2007) and of the Department of Audiology at Lund University Hospital, Sweden (1989-2003).             Dr. Konradsson is the Honorary Secretary for International Association of Physicians in Audiology. His clinical experience includes diagnostics and rehabilitation of hearing disorders in children and adults, including treatment with middle ear, cochlear, and brain-stem implants. Dr. Konradsson’s research includes recordings of vibrations of the human eardrum, relation of OAEs, labyrinthine and middle ear pressure changes, and influence of ME pressure changes on the labyrinth. He has published over 25 peer reviewed scientific papers for medical journals such as Ear & Hearing, Laryngoscope, Audiological Medicine, and Acta Otolaryngologica (Stockholm).