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Universal Hearing Screening

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Universal Hearing Screening
P. Nagapoornima, A. Ramesh2, Srilakshmi3, Suman Rao, P.L. Patricia, Madhuri Gore1, M. Dominic and
Swarnarekha

St John’s Medical College Hospital, Bangalore and 1S.R.C. Institute of speech and hearing, Bangalore



                                                           ABSTRACT
Objective. To determine the weighted incidence of hearing impairment in a standardized population of at risk and not at risk
neonates seeking care at a tertiary level hospital in India.

Methods. A prospective study of a nonrandomized cohort of 1769 neonates (1490 : Not at risk ; 279 : At risk ) from a total of
8192 neonates (6509 : Not at risk; 1683 : At risk ) who sought care at St John’s medical College hospital from 1st September
2002 to 31st March 2006 were screened for hearing impairment using transient evoked otoacoustic emissions .Weighting was
performed using the expected value of 10 % at risk and 90 % not at risk infants in a typical tertiary care level center in India
derived from the National Neonatology and Perinatology database 2002 – 2003. Z test and 95 % confidence interval was used
to determine the external validity of the results.P less than 0.05 was considered as statistically significant.The power of the study
is 90 %.

Results. The incidence of hearing impairment in infants screened was 10 per 1769 infants screened (1490 : Not at risk ; 279
: At risk) which is 5.65 per 1000 screened. 279 at risk infants were screened and 3 were detected to have hearing impairment
which is an incidence of approximately 10.75 per 1000 screened. Of the 1490 not at risk infants screened 7 had hearing
impairment that is 4.70 per 1000 screened. If this was extrapolated to a standardized population consisting of 10 % at risk and
90 % not at risk then the incidence would be 5.60 per 1000 screened with a 95 % confidence interval of 4.13 – 7.06 . This narrow
95 % confidence interval with a p equal to 0.001 indicates that this value may be close to the caseload in a typical tertiary care
center.

Conclusion. In this study the incidence of hearing impairment is 3 per 279 in at risk infants screened and 7 per 1490 in not at
risk infants screened. The weighted incidence in a standardized population of neonates seeking care at tertiary level center
in India is 5.60 per 1000 as per this study. This high incidence calls for all pediatricians to consider incorporating a basic hearing
screen for all the neonates using cost effective and appropriate technology. Initial screening may be performed using behavioral
observation techniques and confirmation by otoacoustic emissions. [Indian J Pediatr 2007; 74 (6) : 545-549]
E-mail : lavirams@yahoo.com

Key words : Neonatal; Infant hearing screening


Incidence of hearing impairment in a standardized                    regardless of the degree of hearing impairment.3 Most of
population of neonates at risk and not at risk to develop            the neonatal facilities in the United states and European
hearing impairment ranges from 6-60 per 1000 neonates                union have enforced mandatory screening of all
with an average of 4 per 1000 neonates. 1 As hearing                 newborns. These programs have demonstrated a definite
impairment is a hidden disability it is usually detected             reduction in the age of detection of hearing impairment.
after 2 yr of age. 2 Late detection causes irreversible              4
                                                                       This study has used otoacoustic emissions as the
stunting of the language development potential of the                screening tool. Otoacoustic emission was used this study
child. Detection and rehabilitation of hearing impairment            as it is very sensitive , noninvasive , cost and time
in infants by 6 mth of age has a proven advantage over               effective making it an ideal screening method.5
those detected after 6 mth to acquire normal language
                                                                        Till date there has been no large scale incidence studies
                                                                     among the neonates in the Indian context. This
                                                                     benchmark study intends to examine the incidence in a
Correspondence and Reprint requests : Dr. A. Ramesh, Assistant       cohort of 1769 neonates who sought care at St John’s
Professor, Department of Otolaryngology Head and Neck surgery, St    Medical college hospital, Bangalore over a period of 3 and
John’s Medical College Hospital, Bangalore – 560034                  a half yr. This data maybe used in the formulation of
[Received July 19, 2006; Accepted December 29, 2006]                 proposals to policy making bodies in order to get grants

Indian Journal of Pediatrics, Volume 74—June, 2007                                                                               545
                                                                                                                           30

                                                   P. Nagapoornima et al

to implement a national universal neonatal hearing                4.	 Craniofacial anomalies including those with
screening program. Also private institutions can take the             morphologic abnormalities of the pinna and ear
lead in establishing self sustaining and affordable                   canal.
screening programs in their facilities.                           5.	 In-utero infections by TORCH group of organisms
                                                                  6.	 Parental concern
                                                                  7.	 Severe birth asphyxia requiring ventilation
              MATERIALS AND METHODS                               8.	 Hyperbilirubinemia requiring exchange transfusion
                                                                    The working definitions of morbidities in the at risk
A prospective study of a nonrandomized cohort of 1769            group in this study are derived from the national
neonates (1490 : Not at risk ; 279 : At risk ) from a total of   neonatology and perinatology database report 2002 –
8192 neonates ( 6509 : Not at risk ; 1683 : At risk ) who        2003 and are as follows.6 Severe birth asphyxia : Apgar
sought care at St John’s medical College hospital from 1st       score of 3 or less at 1 minute of age, Hyperbilirubinemia
September 2002 to 31st March 2006 were screened for              requiring exchange transfusion : serum bilirubin level >
hearing impairment using the following test protocol.            20 mg/dl, respiratory distress : presence of at least 2 of
Transient evoked Otoacoustic emissions (OAE ) were               the following criteria – respiratory rate more than 60 per
used as the first level of screening by 6 weeks of age.The       minute/subcostal or intercostals recessions/expiratory
failed neonates underwent a second screen within 3               grunt or groaning, meningitis and sepsis had to be
weeks of first screen. Auditory brainstem response and           culture positive for CSF and blood respectively.
behavioural audiometry was used to confirm the hearing           Statistical Analysis
loss if the neonates failed the second OAE screen..
Professionals from the following specialties constituted         Internal validity : The otoacoustic emission analyzer and
the neonatal hearing screening team : Neonatology,               auditory brain stem response equipment were calibrated
Audiology, Otorhinolaryngology, Child psychology,                and the protocol driven measurement ensured internal
Neurology and Medicosocial work.                                 validity.
Specification of the equipment and criteria for pass and         External validity : The Z test was used to test the external
fail                                                             validity. As there are no large scale Indian studies on
                                                                 incidence of hearing impairment the reference values
The program was initiated in September 2002 using                were drawn from the American Joint Committee
automated equipment Echo screen sw-rev 6.8, fischer­             statement on Infant hearing screening 2000. The
zoth and an equipment hired form the S.R.C Institute of          information of this cohort were used to calculate the
speech and hearing Bangalore. Till September 2004                probable incidence in other neonatal care centers by
screening was done on once a week basis for only high            examining the distribution of risk factors in various
risk infants. From October 2004 , we acquired an ILO 292         centers. This data was drawn from the national
USB -1 otoacoustic emission (OAE) analyser. Since, then          neonatology and perinatology database report 2002 –
screening of high risk as well as not at risk infants were       2003.6 Statistical package for social sciences (SPSS) version
done on all the working days. The criteria for passing was       10 was used to calculate these projections and obtain 95%
a signal noise ratio of 3dB in at least 3 frequencies bands.     confidence intervals. P value less than 0.05 was taken as
Auditory brain stem response (ABR) and behavioral                statistically significant. The power of the study is 90%.
observation audiometry (BOA) was used to confirm if the
child failed the OAE screen 2 times. Follow up was done
using Receptive expressive emergent language                                             RESULTS
scale(REELS) and Behavioural observation audiometry
(BOA).
                                                                 Incidence in the cohort of all infants screened
   The neonates were grouped as at risk to develop
                                                                 Table 1 shows the incidence of hearing impairment in
hearing impairment if one of the following was
                                                                 1769 infants screened (1490 : Not at risk; 279 : At risk) was
present.These criteria were adapted from the American
                                                                 10 which is 5.65 per 1000 screened. The 95 % percent
Joint Committee statement on Infant hearing screening
                                                                 confidence interval was between 2.15 – 9.15 infants per
(JCIH), 2000.5
                                                                 1000 screened. This finding was highly significant with p
 1.	 An illness or condition requiring admission of 24           = 0.001.
     hours or more to a NICU.
                                                                 Incidence in no risk newborns
 2.	 Stigmata or other findings associated with a
     syndrome known to include a sensorineural and / or          Table 1 shows that in the 1490 infants screened 7 had
     conductive hearing loss.                                    hearing impairment that is approximately 4.70 per 1000
 3.	 Family history of permanent childhood sensorineural         screened. The 95 % percent confidence interval was
     hearing loss                                                between 1.22 – 8.17 infants per 1000 screened. This

546                                                                     Indian Journal of Pediatrics, Volume 74—June, 2007
31

                                                    Universal Hearing Screening

TABLE 1. Incidence of Hearing Impairment in a Cohort of at Risk and not at Risk Infants (N=1769)

Infant cohort                                     Incidence in          Incidence                95% confidence             p value
                                                   the cohort           expressed                  interval in a            by Z test
                                                                         per 1000                 population of
                                                                         screened                 1000 screened

All infants                                       10 per 1769              5.65                     2.15 – 9.15              0.001
At risk infants                                    3 per 279               10.75                    1.42 – 2.29              0.001
Not at risk infants                                7 per 1490               4.70                    1.22 – 8.17              0.001
Standardized population of
neonates consisting of 10 % at                         -                   5.60                     4.13 – 7.06              0.001
risk and 90 % not at risk

*p values were calculated based on American Academy of Pediatrics ,data.

finding was highly significant with p = 0.001. The median             :1,pre auricular skin tags :1 ,osteogenesis imperfecta :3
weight was 2.98 kg with a skewness of 0.61. The median                and hydrocephalus:1. Down’s syndrome was the most
gestation was 38 weeks with a skewness of 0.91.                       common syndrome seen.
Incidence in the at risk newborns                                        Table 3 shows the distribution of infants with prenatal
                                                                      and post natal infections requiring NICU admission.
279 at risk infants were screened and 3 were detected to
                                                                      There was no infant in these groups detected to have
have hearing impairment which is an incidence of
                                                                      hearing impairment. Retroviral infection and pneumonia
approximately 10.75 per 1000 screened. The 95% percent
                                                                      were the most common prenatal and post natal infection
confidence interval was between 1.42 – 2.29 per 1000
                                                                      respectively. The absence of hearing impairment even in
screened with a high statistical significance of p = 0.001.
                                                                      neonates with meningitis could be due to the low number
The incidence in various groups of infants with the risk
                                                                      screened or the absence of Hemophilus influenzae as the
factors is shown in Table 2. The highest incidence seen
                                                                      etiological factor in any of the cases screened. The highest
was is infants with family history of childhood onset
                                                                      incidence is seen in H.influenzae meningitis.5
sensorineural hearing loss. The infants with severe birth
asphyxia was the other group with an incidence of 1 per               TABLE 3. Distribution of Various Prenatal and Post Natal
51 screened. None of the other groups had any infant                           Infections Among Infants Screened for Hearing Loss
with hearing impairment. Though low birth weight (<                            (N=158)
2500 gms) had not been included in the JCIH statement,                Nature of infection                   Number of infants screened
in this cohort we found an incidence of 2 in 262 infants
screened that is 7 per 1000 screened. The weight of the               1.	 Congenital Reubella                           3
two infants with hearing impairment was 1.1 and 1.5 Kgs.                  Syndrome
                                                                      2.	 Hepatitis B (Maternal)                        2
TABLE 2. Distribution of at Risk Infants (N=279)                      3.	 Cytomegalovirus (Maternal)                    2
                                                                      4.	 Chickenpox (Maternal)                         1
Risk factor                      No. of infants      No. of infants   5.	 Syphilis (Maternal)                           1
                                  Screened           with hearing     6.	 Retrovirus infection (Maternal)               4
                                                      impairment      7.	 Respiratory distress suggestive              96
                                                                          Of pnuemonitis
Family history of                                                     8.	 Septicemia (Postnatal)                       32
childhood onset                          8                 2          9.	 Meningitis (Postnatal)                       14
sensorineural loss                                                    10. Hepatitis (Postnatal)	                        3
Craniofacial anomalies                  24                 0              Total                                       158
Severe birth asphyxia                   51                 1
Pre and post natal infections                                         Risk comparison of at risk and not at risk neonate to
requiring NICU                        158                  0
                                                                      have hearing impairment
Hyperbilirubinemia                     38                  0
requiring exchange transfusion                                        In this study there was no statistically significant
Total                                 279                  3
                                                                      difference in the incidence of hearing impairment
                                                                      between at risk and not at risk infant. (P=0.20 : Fisher’s
   There were no cases detected with hearing impairment               exact test) However the at risk infant has a relative risk of
in the group with craniofacial anomalies.The various                  2.29 (95% confidence interval of 0.60 – 8.80) in
craniofacial anomalies seen were antimongoloid slant: 5,              comparison to not at risk infant to have hearing
microcephaly: 4, cleft palate : 3, microtia : 2, dandy                impairment.
Walker syndrome : 1, microtia with pre-auricular skin tag
                                                                      Results of the protocol used to screen
and facial palsy: 1, pierre robin syndrome : 1, occipital
encephalocoele : 1, preauricular skin tag with facial palsy           The following flow chart shows the results of various

Indian Journal of Pediatrics, Volume 74—June, 2007                                                                                      547
                                                                                                                                      32

                                                   P. Nagapoornima et al

levels of screening as per the protocol used in the              implement universal hearing screening.
program. Otoacoustic emission passed first time : 1662 →
                                                                 High risk or Universal screening : Where to begin ?
Otoacoustic emission failed first time and passed second
time :97 → Otoacoustic emission failed first and second          This pilot study in India has shown that screening of
time and ABR failed : 10. These were evaluated using             only at risk neonates can miss detection of 70 % of the
behavioural observation audiometry to confirm hearing            newborns with hearing impairment. Though incidence
impairment.The referral rate for a second screen was 5.5         per 1000 is higher among at risk infants, focusing only on
% and the referral for an ABR was 0.6 %.                         the at risk infants may miss 50 % of the newborns with
                                                                 hearing impairment . 11,12,13,14,15,16 If the resources are
                                                                 limited then one could focus initially on at risk neonates
                       DISCUSSION
                                                                 and gradually implement universal screening .

The incidence of hearing impairment in this cohort is 5.65
                                                                                         CONCLUSIONS
per 1000 screened. If this was extrapolated to a
standardized population consisting of 10 % at risk and 90
% not at risk then the incidence would be 5.60 per 1000          A high incidence of hearing impairment of 5.60 per 1000
screened with a 95% confidence interval of 4.13 – 7.06.          in a standardized neonatal population of at risk and not
This narrow 95% confidence interval with a p = 0.001             at risk warrants the urgent implementation of universal
indicates that this value may be close to the caseload in a      hearing screening of all the neonates in India. Screening
typical tertiary level hospital in India. The assumption of      only at risk neonates can miss upto 70 % of all the
10 % to be at risk was calculated by projecting the              neonates with hearing disability in a typical tertiary care
distribution from Neonatal database 2002 -2003. 6 An             hospital. In this study there is no statistically significant
ICMR supported Community based disability survey has             difference in the incidence of hearing impairment
detected incidence of congenital hearing loss as 10 per          between at risk and not at risk infants. Cost effective and
thousand and 20 per thousand in rural and urban India            appropriate behavioural methods may be used if
respectively. 7,8 Another study undertaken in rural              resources are limited and use Otoacoustic emissions test
Karnataka has detected 8 children per thousand with              to confirm.The final goal should be to screen all neonates
congenital hearing loss.9                                        using automated Otoacoustic emission technology.
   This is a very high incidence in relation to other            Acknowledgements
congenital defects for which cure can be provided.10 The
                                                                 The authors acknowledge Dr GRK. Sarma , Dr Vijayaraman , Ms
findings of this study correlates well with most of the          Eliza Perreira and the management of St John’s National Academy
large scale studies in the United states and European            of Health Sciences for their unflinching support of the program.
union. So there is no significant difference in the case load    Special thanks for Christoffel Blinden mission for the grant that
per 1000 seen in India in comparison to the developed            aided in the purchase of OAE analyzer.
nations. The incidence may vary based on high risk
population characteristics in different set ups.
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548                                                                     Indian Journal of Pediatrics, Volume 74—June, 2007
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                                                     Universal Hearing Screening

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Indian Journal of Pediatrics, Volume 74—June, 2007                                                                                        549

				
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