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International Journal of Pediatric Otorhinolaryngology 76 (2012) 1366–1369
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International Journal of Pediatric Otorhinolaryngology
journal homepage: www.elsevier.com/locate/ijporl
The performance of distortion product otoacoustic emissions and automated
auditory brainstem response in the same ear of the babies in neonatal unit
Siti Noor Hidayah Abdul Wahid a, Mohd Khairi Md Daud b,*, Dinsuhaimi Sidek b,
Normastura Abd Rahman c, Suzana Mansor d, Mohamad Normani Zakaria a
a
School of Health Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
Department of Otorhinolaryngology Head and Neck Surgery, School of Medical Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
c
School of Dental Sciences, Health Campus, Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
d
Audiology Clinic, Hospital Universiti Sains Malaysia, 16150 Kubang Kerian, Kelantan, Malaysia
b
A R T I C L E I N F O
A B S T R A C T
Article history:
Received 22 March 2012
Received in revised form 12 June 2012
Accepted 15 June 2012
Available online 6 July 2012
Objective: To identify the outcomes of hearing screening using different protocols of both Distortion
Product Otoacoustic Emissions (DPOAE) and Automated Auditory Brainstem Response (AABR) tests in the
same ear of the babies in a neonatal unit population.
Methods: A cross-sectional study was carried out on babies who were admitted into a neonatal unit. By
using a formula of single proportion and considering 20% drop out, the number of sample required was
114. The subjects were chosen by using a systematic random sampling. The infants selected were
subjected to DPOAE followed by AABR tests screening at the same setting before discharge.
Results: There were 73 newborns (61.6% male and 38.4% female) participated in this study with a total of
146 ears screened. Ototoxic medication was the most common risk factor followed by hyperbilirubinaemia and low birth weight. AABR had higher passing rate (82.9%) as compared to DPOAE (77.4%).
The highest passing rate was achieved if the protocol of either passed DPOAE or AABR was used (90.4%).
The rate was lower when auditory neuropathy spectrum disorder (ANSD) has been considered (82.9%).
Hyperbilirubinaemia, prematurity, craniofacial malformation and ototoxic drugs seem to be the high risk
factors for auditory neuropathy.
Conclusion: AABR has a higher passing rate as compared to DPOAE. However, the use of both instruments
in the screening process especially in NICU will be useful to determine the infants with ANSD who may
need different approach to management. Therefore, a protocol in which newborns are tested with AABR
first and then followed by DPOAE on those who fail the AABR is recommended.
ß 2012 Elsevier Ireland Ltd. All rights reserved.
Keywords:
Hearing tests
Neonatal screening
Auditory neuropathy
1. Introduction
Hearing is necessary to learn language and speech. The
abnormal functioning auditory system will affect the social,
emotional and intellectual development of the children. Early
detection and intervention will help minimising such effects.
Therefore, newborn hearing screening programme has been
advocated.
It is known that the prevalence of significant hearing loss
appears to be one to three in a thousand child births [1–5].
Therefore it is considered as the most common congenital deficit in
humans. This value could become one to five in 100 if only babies
in the neonatal intensive care unit (NICU) and infants selected from
at-risk registers are considered [6–11].
Otoacoustic emissions (OAE) and automated auditory brainstem response (AABR) are the two types of screening technologies
commonly used in newborn hearing screening programme. Both
procedures are quick and painless and have been demonstrated
practical and effective. Depending on the protocols used, either
type can be used alone or in sequence. This study was aimed to
identify the outcomes of hearing screening using different
protocols of both DPOAE and AABR in a neonatal unit population
which caters for the graduates of Neonatal Intensive Care Unit
(NICU) and the infants who are unwell that need admission to the
ward.
2. Methodology
* Corresponding author. Tel.: +60 9 7676413; fax: +60 9 7664093;
mobile: +61 2 9286091.
E-mail address: [email protected] (M.K. Md Daud).
0165-5876/$ – see front matter ß 2012 Elsevier Ireland Ltd. All rights reserved.
http://dx.doi.org/10.1016/j.ijporl.2012.06.008
A cross-sectional study was carried out on the children who
were admitted into a neonatal unit, Hospital Universiti Sains
S.N.H. Abdul Wahid et al. / International Journal of Pediatric Otorhinolaryngology 76 (2012) 1366–1369
3. Results
There were 73 newborns (61.6% male and 38.4% female)
participated in this study with a total of 146 ears screened. The
majority of the participants were Malays (98.6%) and only 1 (1.4%)
was Chinese. This reflects the actual racial composition of the
population.
Table 1 shows the risk factors for the infants involved in this
study. Ototoxic medication was the most common risk factor
followed by hyperbilirubinaemia and low birth weight.
Fig. 1 shows the number of risk factors per child. Nearly half of
the babies in the neonatal unit did not have any risk factors for
hearing impairment. Forty one percent of the infants had at least
one risk factor, 12 percent had two risk factors while about 1
percent had three, four and five risk factors.
Table 2 shows the outcomes of hearing screening by ears
according to different protocols used. AABR had a higher passing
rate (82.9%) as compared to DPOAE (77.4%). The highest passing
rate was achieved if the protocol of either passed DPOAE or AABR
Table 1
Risk factors for hearing loss.
Risk factor
n (%)
Significant family history
In utero infection
Craniofacial anomalies
Birth weight < 1500 g
Hyperbilirubinaemia
Ototoxic medication
Bacterial meningitis
Low Apgar score (0–4 at 1 min, 0–6 at 5 min)
Mechanical ventilation lasting 5 days or more
Congenital anomalies (with risk of deafness)
1
1
1
4
7
37
1
2
1
3
(1.4)
(1.4)
(1.4)
(5.5)
(9.6)
(50.7)
(1.4)
(2.7)
(1.4)
(4.1)
45
42.5
Case
41.1
40
35
30
Percentage
Malaysia. The neonatal unit receives almost all the NICU graduates
who are stable enough while waiting to be discharged. The unit
also receives the problematic infants who do not need NICU
treatment such as mild to moderate neonatal jaundice.
The sample size was calculated using single proportion formula
based on the prevalence of babies who were at risk for hearing loss
at 44% [12]. The calculation indicated that minimum sample size of
95 subjects would be sufficient to obtain the 0.1 precision in
calculating the prevalence of babies who were at risk for hearing
loss with 95% confidence interval (CI). With anticipation of 20%
non-response rate, it was decided to take 114 subjects.
All infants in the neonatal unit were included in this study. They
were chosen by using a systematic random sampling. The conditions
of the ears were assessed by using an otoscope. The infants with
impacted ear wax, middle ear effusion and persistent mesenchyme
or amniotic fluid in the external ear were excluded from the study.
The infants selected were subjected to DPOAE (Eclipse OAE,
Interacoustic, German) with the frequencies used at 2, 3, 4 and
5 kHz followed by AABR (ABRis, Interacoustic, Germany) screening
tests at the same setting as near to discharge as possible. The tests
were done in their bassinets in the neonatal unit itself. No sedation
was given and whenever possible neonates were tested in sleeping/
quiet state, after feeding and/or bathing. Both instruments produced
a ‘‘pass’’ or ‘‘refer’’ result and did not require any special skills for the
interpretation of the results. The tests were repeated two times in
cases with ‘‘refer’’ result. Data were entered and analysed using SPSS
version 12.0. Descriptive statistics such as frequency and percentages were calculated for all the categorical variables.
Ethical approval was obtained from Research Ethics Committee
(Human), Universiti Sains Malaysia (Ref.: USMKK/PPP/JEPeM
(219.3.(14.1)).
1367
25
20
15
12.3
10
5
1.4
1.4
3
4
1.4
0
0
1
2
5
Fig. 1. The percentage of risk factors found per child.
was used (90.4%). The rate was lower when auditory neuropathy
spectrum disorder (ANSD) has been considered (82.9%).
Table 3 shows the high risk factors in the patients with the
possibility of having ANSD. Except in one case (case no. 2),
hyperbilirubinaemia, prematurity, craniofacial malformation and
ototoxic drugs seem to be the high risk factors for auditory
neuropathy.
4. Discussion
Universal newborn hearing screening is becoming a standard
programme in many centres nowadays. Early identification of
hearing loss with early medical and educational interventions has
been demonstrated to significantly improve communication skills
and cognitive ability. Most of the centres are using AABR and OAE
for the screening as they are sensitive and specific to the
identification of hearing losses but with no standard protocols.
In this study, the prevalence of passing rate using DPOAE test
was 77.4 percent. The passing rates for the first screening using
OAEs vary depending on the different centres and group of the
neonates studied. They were ranging from 66.7% to 93.5% [13–19].
In NICU babies, the different aetiologies have different referral
rates [20]. Their failure rate was usually higher than the well
babies’ resident [21]. The presence of OAEs provides direct
evidence of the existence of an active mechanism in the cochlea.
However, OAEs will be absent if there is a significant external and/
or middle ear problems. Besides that, DPOAE test must be done in
environment where it is quiet, infants are in calm condition and the
probe tip is snugly fitted in order to get the reliable results. In the
present study, the passing rate can be considered low as compared
Table 2
The outcomes of hearing screening on each ear according to different protocols.
Protocol
n
%
Passed DPOAE
Passed AABR
Either passed DPOAE
or passed AABR
Either passed DPOAE
or passed AABR excluding
passed DPOAE with failed
AABR (auditory neuropathy)
Passed both DPOAE and AABR
113
121
132
77.4
82.9
90.4
121
82.9
102
69.9
S.N.H. Abdul Wahid et al. / International Journal of Pediatric Otorhinolaryngology 76 (2012) 1366–1369
1368
Table 3
High risk factors related with auditory neuropathy.
Case
Sex
Ear affected
Risk factor (associated conditions)
1
2
3
4
5
6
7
8
Male
Male
Male
Female
Male
Male
Male
Female
Bilateral
Right
Right
Bilateral
Bilateral
Left
Left
Left
Ototoxic drugs
None
Ototoxic drugs, neonatal jaundice
Neonatal jaundice
Cleft palate and lip, ototoxic drugs
Premature, neonatal jaundice, ototoxic drugs
Premature, ototoxic drugs
Neonatal jaundice
concentration at which exchange transfusion is indicated had
audiological findings of ANSD [32]. Coenraad et al. showed a
significant association between vancomycin administration and
ANSD compared to controls [33]. Among 37 children diagnosed
with ANSD, Beutner et al. found 2 cases whom related to complex
syndromal diseases [34]. Maris et al. demonstrated aplasia/
hypolasia of the cochlear nerve in MRI of the infants with ANSD
[35]. In contrast to acquired causes, congenital ANSD has been
found to be associated with genetic abnormality [36].
5. Conclusion
to many other centres. Since the study was done in the neonatal
unit itself, the background noise in the ward may have contributed
to its lower rate.
In our finding, the passing rate of using AABR test was 82.9%. It
was higher than the passing rate using DPOAE. Vohr et al. and
Benito-Orejas et al. have shown that AABR gave significantly better
passing rates as compared to TEOAEs [13,15]. The AABR test
measures the electrical activity beyond the cochlea until the lower
brainstem level and in contrast to OAEs test, it is less affected by
the outer, middle and/or inner ear disorders. Therefore, the
utilisation of AABR technology rather than OAE will further
improve the values of passing rate and false positive. However,
similarly to OAEs, the results of AABR test is also subjected to the
influence of factors such as the environmental noise, child
condition and equipment condition during the testing.
The prevalence of passing rate using either passed DPOAE or
AABR test was 90.4%. As expected, it was higher than the passing
rate using single test such as DPOAE only and AABR only. For this
combination protocol, the failures could be either passed DPOAE
but failed AABR or failed DPOAE but passed AABR or failed both of
the tests. The result of passed DPOAE but failed AABR may suggest
ANSD while the result of failed DPOAE but passed AABR may be due
to the external factors involved in the DPOAE test which suggests
the possibility of false positive.
When the passing of both DPOAE and AABR was considered as
passed, the passing rate became 69.9%. Olusanya and Bamigboye
labelled this group of infants as true-negatives [22]. In their study,
the passing rate was even lower at 60.7%. Therefore, the use of such
a protocol will result in a very high referral rates.
Another important issue on hearing screening especially in
those babies in NICU is ANSD. In our study, there were 7.53% ears
were suspected to have ANSD. Further auditory evaluations are
very important to confirm and differentiate it from sensorineural
hearing loss (SNHL) as it may need different approach to
management. The prevalence of ANSD were ranging from 1.42%
to 24.0% in different groups of patients of hearing impaired
children and those with at risk for hearing impairment [23–28]. All
of these hearing-impaired children were not detected using TEOAE
alone and therefore necessitate the used of AABR. The Joint
Committee on Infant Hearing (JCIH) in its year 2007 position
statement has recognised that neural conduction disorders results
in adverse communication outcomes [29]. Because this disorder
typically occurs in children who require NICU care, the committee
recommends screening on this group with AABR. Nevertheless,
since ANSD shows normal oto-acoustic emissions, the combined
use of DPOAE and AABR testing will lead to the recognition of the
disorder easier.
As far as the risk factors for ANSD are concerned, hyperbilirubinaemia, prematurity, the use of ototoxic drugs and craniofacial
malformation seem to be related with it. Sanyelbhaa Talaat et al.
reported hyperbilirubinaemia as the most common cause of ANSD
[30] while Foerst et al. found it to be the second commonest after
prematurity with postpartal complications [31]. Saluja et al.
reported that 6 out of 13 neonates with total serum bilirubin
AABR has a higher passing rate as compared to DPOAE.
However, the use of both instruments in the screening process
especially in NICU will be useful to determine the infants with
ANSD who may need different approach to management.
Therefore, a protocol in which newborns are tested with AABR
first and then followed by DPOAE on those who fail the AABR is
recommended.
Acknowledgements
We would like to thank the Universiti Sains Malaysia for
providing financial support for this study, via their incentive grant
(304/JPNP/600004).
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