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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 26  |  Issue : 2  |  Page : 85-88

A study of incidence of hearing loss in newborn, designing a protocol and methodology to detect the same in a tertiary health-care center


1 Department of Otorhinolaryngology, Yenepoya Medical College, Mangalore, Karnataka, India
2 Department of Paediatrics, Yenepoya Medical College, Mangalore, Karnataka, India

Date of Submission17-Apr-2020
Date of Acceptance12-Jun-2020
Date of Web Publication17-Jul-2020

Correspondence Address:
Dr. K S Gangadhara Somayaji
Yenepoya Medical College, Mangalore, Karnataka
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/indianjotol.INDIANJOTOL_63_20

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  Abstract 


Background: Hearing impairment can have a negative impact on an individual's social, educational, and emotional life. If not detected early, it can affect the speech and language development. This delay in diagnosis and intervention can be mitigated by mandatorily implementing newborn hearing screening protocols. Objective: The primary objective of this study was to find the incidence of hearing loss in normal and high-risk neonates and recommend a protocol for the detection of hearing loss in the neonate. Materials and Methods: The study was carried out in a tertiary care teaching hospital over a period of 12 months. A total of 1000 babies including 693 normal and 307 high-risk babies were enrolled into the study. All neonates underwent otoacoustic emission (OAE) within the first 3 days of birth. Those who failed in this test underwent repeated OAE after 6 weeks, followed by brain stem-evoked response audiometry (BERA) if the second OAE was negative. Results: Of 307 high-risk babies, 48 showed absent OAE on initial screening. On follow-up, 10 babies still showed absent OAE. BERA was positive for hearing loss in five and normal in the other five babies. Among 693 normal neonates, 71 had absent OAE during the first test. On subsequent OAE test, seven babies failed whose BERA showed hearing loss in five and normal hearing in two babies. Conclusion: A proper protocol and methodology is required for the early detection of hearing loss so that rehabilitation can be started at the earliest. In this study, the incidence of hearing loss is found to be more in high-risk neonates as compared to normal ones. As OAE is simple and quick, it is preferred for screening, but BERA is required for the definitive diagnosis.

Keywords: Brain stem-evoked response audiometry, neonatal hearing screening, otoacoustic emission


How to cite this article:
Nishad A, Gangadhara Somayaji K S, Mithun H K, Sequeira N. A study of incidence of hearing loss in newborn, designing a protocol and methodology to detect the same in a tertiary health-care center. Indian J Otol 2020;26:85-8

How to cite this URL:
Nishad A, Gangadhara Somayaji K S, Mithun H K, Sequeira N. A study of incidence of hearing loss in newborn, designing a protocol and methodology to detect the same in a tertiary health-care center. Indian J Otol [serial online] 2020 [cited 2020 Aug 12];26:85-8. Available from: http://www.indianjotol.org/text.asp?2020/26/2/85/289950




  Introduction Top


Hearing is one of the most important special senses needed for the development of an individual. Any impairment in hearing can affect one's speech and language development, reflecting the same in his social, emotional, and educational field.[1] Hearing loss and deafness are global issues that affect at least 278 million people worldwide.[2] In a study, it has been shown that 1.2–5.7 per thousand neonates seem to be affected with congenital hearing loss.[3] Due to the need for special awareness and occupational limitations, prelingual onset hearing loss has caused a more economic burden. Use of less reliable modalities during screening and late diagnosis are the causes for concern.[4] This can be overcome by implementing proper hearing screening methods in newborn which can enable accurate diagnosis of the hearing loss at the earliest. This can help in early intervention. It is significant to know that the basal maturation of the auditory pathway is nearly completed at 2 years of age.[1] Clinically, it is difficult to detect the hearing loss in newborns. Hence, otoacoustic emission (OAE) and brain stem-evoked response audiometry (BERA) are the two tests widely used for this purpose. OAE is an objective test to determine the cochlear status, especially the outer hair cells, and BERA tests the functional integrity of the auditory pathway from the eighth nerve to lower brainstem. Since OAE is simple, quick, and inexpensive, it is used more often than BERA for screening procedure.[5] Loss to follow-up and cost remain as major issues of this study.[6] We have done this study to find the incidence of hearing loss in normal as well as high-risk newborn at our tertiary care hospital and to develop a protocol and methodology for detecting hearing loss in the newborn and in those in high-risk groups. The incidence of hearing loss is expected to be more in high-risk neonates than in normal neonate.[7]


  Materials and Methods Top


This study was conducted in the department of ear, nose, and throat in a tertiary care teaching hospital, from over a period of 1 year. A total of 1000 babies born during this period were enrolled in the study. Ethical clearance for the study was obtained from the institutional ethics committee. Detailed history regarding prenatal, natal, and postnatal period was taken from the mother. High-risk category was defined. History included demographic details, family history of deafness and consanguinity, gestational history of the mother, intra-natal and postnatal events, and complications. Low birth weight baby, preterm baby, delivery by cesarean section, twin gestation, birth asphyxia, congenital anomalies, neonatal jaundice, newborns with a history of convulsions, and infection were categorized into high-risk group. Positive antenatal history of any fever with rashes, radiation exposure, teratogenic drug intake, hypertension, diabetes, hypothyroidism, and Rh incompatibility were also considered as risk factors.

Newborns were clinically evaluated and subjected to screening using OAE on the 3rd day of birth. Those who failed in this test underwent a second screening with OAE at 6 weeks of age, followed by BERA if the repeat OAE was absent.

OAE was done using a portable Neurosoft Neuro-Audio instrument. Neonates were tested when they were sleeping or quiet. Background noise was taken care of while doing the test to avoid false results. An appropriate sized probe was introduced into baby's ear canal and OTE from each ear was recorded with a standardized procedure. The device used click stimuli that covers a frequency range from 700 Hz to 4kH at an intensity of approximately 90 dB SPL. The result of transient evoked OAE was represented in a graph based on response amplitude and signal-to-noise ratio. It displayed the result as “pass” or “refer.”

In BERA, the stimulus was given in the form of a click with the filter setting of 30 Hz to 3000 Hz. It was done using the Neurosoft Neuro-Audio instrument. It was done when the baby is asleep or quiet. Some babies required sedation with syrup promethazine which is safe in the pediatric group. Three disposable electrodes were kept over the forehead (+) and the mastoid process of test ear (−) and nontest ear (ground). The response produced at various levels of the auditory pathway was recorded by the electrodes and amplified through various electrical procedures. The result was obtained in the form of multiple waves and analyzed with regard to morphology, repeatability, and threshold of hearing.


  Results Top


Of 1000 newborns screened, 535 (53.5%) were male and 465 (46.5%) were female. Among the 1000 newborns, 693 (69.3%) were normal and 307 (30.7%) were high-risk babies. Of 693 normal neonates, 335 were female and 358 were males, and among 307 high-risk neonates, 130 were female and 177 were male.

After first otoacoustic emission

Eight hundred and eighty-one babies (88.1%) turned out to have normal hearing. The failed result was observed by 31 (3.1%) in the left ear, 29 (2.9%) on the right ear, and 59 (5.9%) on both the ears. Among 693 normal newborns, 622 passed the initial screening with OAE (89.8%). Left, right, and bilateral fail was shown by 20 (2.9%), 13 (1.9%), and 38 (5.5%), respectively. Of 307 high babies who underwent initial screening using OAE, 259 were found to have normal hearing. Eleven (3.6%) showed left, 16 (5.2%) showed right, and 21 (6.8%) showed bilateral hearing loss.

After the second otoacoustic emission

Ninety four (9.4%) babies passed the test after the second OAE. Hence a total of 975 babies were shown to have normal hearing sensitivity. In the remaining 25, 7 babies (0.7%) showed failed result on the left side, 3 (0.3%) showed on the right side, 7 (0.7%) showed on both the side, and 8 babies were lost to follow-up. After the second OAE, 62 passed making the number of normally hearing babies as 684. Of the remaining babies, the negative results were showed in the left side by 5 and on both the sides by 2. Two babies were lost to follow-up. With 2nd OAE test,32 (10.4%) were found to be normal in their hearing. Left, right, and bilateral fail was found in 2 (0.7%), 3 (1%), and 5 (1.6%), respectively.

After brain stem-evoked response audiometry

Of 1000 newborns screened, the number of babies subjected to BERA to confirm hearing loss was 17. Of this, 7 babies Showed normal hearing. Hearing loss was seen in 10 babies. 3 had hearing loss on the left side and seven had bilateral hearing loss. Among these, ten babies with hearing loss, seven were female and three were male. In the female babies, two were with left-sided hearing loss and five were with bilateral hearing loss. In the male babies, only one had left hearing loss and two were with bilateral hearing loss.

Among the 17 babies who underwent BERA, 10 were normal babies and 7 were high-risk babies. Five babies in each group had hearing loss. In the normal category, only one showed left-sided hearing loss and four showed bilateral hearing loss. Among the high-risk category, two showed left-side hearing loss and three had hearing loss in both the ears.


  Discussion Top


Congenital hearing impairment is said to affect 2–3 in 1000 newborns.[8] Congenital deafness is one of the most common sensorial deficits presenting at birth.[9] Nearly 50% of the cases of deafness in children follow genetic etiology and involve single-gene mutation.[10] The rest are due to environmental causes.[11] Mutations may be in the genes involved in the auditory pathway, labyrinthine homeostasis, or mechanoelectrical transduction. In developed countries, genetic causes account for the maximum number of cases.[12] Infection is the main reason in developing countries. Congenital sensorineural hearing loss was calculated to be 1.2–5.7/1000 live births.[13]

American Academy of Paediatrics Task Force on newborn and infant hearing advises universal hearing screening within 3 months of life and offers necessary intervention by the age of 6 months.[14] The Joint Committee on Infant Hearing (JCIH) hastens this timing to soon after delivery or before their discharge from hospital. The 2007 guidelines of JCIH recommend the screening of all newborns within the 1st month of life. Those who fail the initial test should undergo a detailed hearing assessment before 3 months of age. Confirmed cases of deafness should be provided with appropriate intervention without a delay of >6 months of age.[15] We adopted a protocol of screening at the 3rd day of life as the babies delivered normally are discharged on the 3rd day at our hospital. In case of abnormal results, the test was repeated at 6 weeks of age. Those failing the OAE again are sent for BERA. Six weeks' time was chosen as the babies were usually called for immunization at 6 weeks to the hospital. Hence, compliance for follow-up is better. For the babies suspected to have hearing loss, necessary interventions are planned at the earliest. This exposes them to sound and spoken language which aids in developing speech. Neural plasticity is highest during the initial few years of life and thus makes them adapt to changes. Hence, the intervention in the earlier period gives better response.[16]

Among the 1000 neonates enrolled in the study, majority (69.3%) were normal babies without any risk factors. Of these 693 newborns, hearing loss was detected in 5 babies by doing BERA. About 30.7% babies were categorized into high-risk neonates. In this group, five babies were diagnosed to have a hearing impairment. This accounts for an incidence of 7.21/1000 live births in normal and 16.2/1000 live births in high-risk neonates. This increased incidence of hearing loss in high-risk group compared to normal ones is in agreement with other studies in the literature. In a study by Rai and Thakur, the incidence was found to be 2.29 in 1000 normal and 49.18 in 1000 risk babies.[7] According to the study by Parab et al. done in a rural place in India for a duration of 3 years, the incidence of hearing loss was calculated as 1.68 in 1000 normal babies and 10.6 in 1000 high-risk babies constituting to an overall incidence of 3.54.[17] Nagapoornima et al. reported the incidence as 10.75 (risk) and 4.7 (normal) per 1000 live births.[18] The incidence of mild-to-profound hearing loss was estimated to be 1%–1.5% in normal and 2.5%–10% in high-risk neonates as per the study by Abdullah et al. done in a Malaysian hospital.[19] A study done in the Northwestern part of India has found that 4 in 1000 newborns were detected with hearing loss, of which three had associated risk factors.[20] Paul AK has measured an incidence of 10.3/1000 live birth and 0.98/1000 live birth in risk- and well-baby categories after his study for a period of 7 years.[21]

In our study, hearing loss was not only confined to high-risk babies but also seen in normal babies though the incidence was less compared to them. Screening only high-risk babies can miss out around 50% of hearing loss. A study done by Ur Rehman et al. had showed that nearly two-third of deafness was seen in normal newborns.[22] Hence, universal hearing screening has to be undertaken which includes screening both the normal as well as high-risk groups.

Odds ratio and P value

Using logistic regression, the odds ratio was calculated to assess the risk of hearing loss in high-risk babies compared to normal babies. It was estimated to be 1.064 after doing the first OAE, 1.006 after the second OAE. It is 1.005 following BERA. It tells that the risk of hearing loss is 1.005 odds high in a high-risk baby compared to a normal one when confirmed with BERA. The corresponding P values were obtained as 0.780, 0.277, and 0.503 after each test. This shows that even though the odds ratio displays a relative risk of deafness in high-risk babies, P value between the two groups exhibiting hearing loss is not significant.

The high chance of false-positive rates encountered when screening is done in the first few days of birth. This can be attributed to the presence of amniotic fluid or vernix in the external auditory canal of the baby which hinders the transmission of OAE.[23] One of the factors which is thought to improve the hearing outcome was breastfeeding.[24] Loss of follow-up is one of the issues which was minimized by calling them for follow-up at the time of immunization.


  Conclusion Top


We followed a protocol of universal newborn hearing screening. On initial screening with OAE, the incidence of hearing loss was 119 in 1000 live births. During the second OAE, it reduced to 17/1000 babies. The overall incidence estimated was 10 in 1000 live births after doing BERA. Our study showed a male preponderance for congenital hearing loss. The incidence was 7.21/1000 live births in normal and 16.2/1000 live births in high-risk neonates. High incidence was shown by the risk category compared to the normal one. We followed a protocol of screening on the third day of life using OAE. Those with suspected hearing loss was checked again with OAE which if found negative, BERA was considered for confirmation of hearing loss. This second testing was planned during immunization visit at 6th week to reduce the loss of follow-up as it is a major issue concerned with the protocol. It was noted that performing the test in the initial period of life can produce a lot of false positives. OAE is a simple test and faster, preferred for the initial screening. It was also observed in our study that screening with only OAE may yield high-false positives and causes unwanted referrals. BERA is time consuming compared to OAE. However, it is essential for confirming the diagnosis.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
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