Study of hearing impairment among “At risk” neonates by screening with OAE

Background: Hearing is one of the very important five senses. Normal speech and language development depend upon a child’s ability to hear spoken language. Universal hearing screening is implemented in many developed countries. However, neither universal screening, nor high risk screening, exists in India. In India various studies have been conducted to detect the hearing loss on high risk neonates. Screening only the high-risk neonates can detect 50% of babies with hearing loss. Hence a mandatory hearing screening is needed to detect all such babies. Methods: A cross sectional study of 75 “At risk” babies were done. Babies underwent hearing screening after 48 hours of birth or before discharge from hospital using DPOAE test as the first level of screening. Babies who got “Refer” results were subjected to repeat testing with DPOAE after one month. Babies who got “Refer” results in the second screening test were referred for diagnostic test BERA to assess hearing loss. Data was analysed by appropriate statistical methodology. Results: Incidence of hearing loss among at risk babies is 2.6 % (2/75). Both babies who had hearing loss had multiple risk factors and had bilateral hearing loss. Common risk factors observed are NICU care > 5 days 100% (2/2), Ventilated baby 50% (1/2), Preterm 100% (2/2), low birth weight 50% (1/2), jaundice requiring phototherapy 100% (2/2). Conclusion: Hearing loss is more common in “At risk” babies. Major risk factors are NICU admission, Preterm, LBW, Ventilated babies, and jaundice. It is necessary to implement neonatal hearing screening of at least “At risk” neonates in our country to secure normal, social and holistic development of the child. Two–stage DPOAE/BERA hearing screening is an efficient and cost-effective method for early detection of hearing impairment on a large scale.


Introduction
Hearing is one of the very important five senses. Normal speech and language development depend upon a child's ability to hear spoken language. Early infancy is the most appropriate time for a child to acquire the foundation of language and communication. Therefore, it is important to find out any problem in hearing early in life so that early intervention can be given to have normal language development [1].
Around 360 million people -5% of the world's population -live with hearing loss which is considered disabling; of these, nearly 32 million are children. The vast majority live in the world's low-income and middle-income countries. The World Health Organization (WHO) estimates that around 60% of childhood hearing loss could be avoided through prevention measures. When unavoidable, interventions are needed to ensure that children reach their full potential through rehabilitation, education and empowerment. Action is needed on both fronts [2].
Hearing impairment in infants should be identified as early as possible to enable interventions to take full advantage of the plasticity of developing sensory system.
All infants with confirmed permanent hearing loss receive services before 6 months of age in interdisciplinary intervention programs that recognize and build on strengths, informed choice, traditions, and cultural beliefs of the family [3].

Original Research Article
Pediatric Review: International Journal of Pediatric Research Available online at: www.medresearch.in 430|P a g e In India, the concept of universal hearing screening does not exist even in high risk babies leave alone normal new-borns.
There are some studies done in India to detect the hearing loss on high risk neonates in very few places.
Hence a Hearing screening program is needed to detect hearing loss among "At risk" new-born babies is needed, and it is the cost-effective approach in developing countries like India.
The recommended hearing screening techniques are either otoacoustic emissions (OAE) testing or auditory brainstem evoked responses (ABRs).
OAE tests, used successfully in most universal newborn screening programs, are quick, easy to administer, and inexpensive, and they provide a sensitive indication of the presence of hearing loss [4].
Hence this study was undertaken to evaluate the burden of hearing impairment among "At risk" neonates born in a tertiary care center by screening with OAE test and to look at the implementation of a hearing screening program in India.

Materials and Methods
Source of data: The source of data for the study are at risk neonates born in VIMS & RC Hospital, Bangalore from Jan 2016 to June 2017. At risk criteria is defined by HRR of JCIH 2007 9 Position Statement.

Study design: A Cross Sectional study.
Sample size: Assuming a population prevalence of 10% "A risk" neonates 10 [with hearing impairment of 2% 4 ] at an alpha value of 5%, with a power of 80%, with an absolute precision of 5%, a minimum of 75 subjects in "At risk" group have been calculated.

Inclusion criteria:
The study includes "At risk" Neonates born in VIMS & RC Hospital during the study period. 75 "At risk" neonates as per JCIH 2007 statement were included in this study.
Exclusion criteria: Neonates whose parent/ guardian not willing for Screening test. Neonates whose parent/ guardian not willing for further follow up if the screening test gives REFER result.

Method of collection of data: Babies born in VIMS &
RC Hospital who fulfil the inclusion and exclusion criteria were included for study. Informed written consent was obtained from parents prior to the study.
All the "At risk" babies underwent hearing assessment after 48 hours of birth or before discharge from hospital using Distortion Product Oto Acoustic Emission [DPOAE] test using a GSI Audera System as the first level of screening.
The test will give a PASS or REFER result. Neonates who get REFER result in the initial screening will be subjected to second screening with DPOAE after one month.
Infants who get REFER results in the screening test twice will be referred for further evaluation by BERA to assess hearing loss.

Results
A total of 75 "At risk" neonates were included into the study during the study period. Risk factors for hearing impairment are as per High risk registry of JCIH 2007 (at risk group).
But none of the neonates studied had maternal history of viral infections or exposure to X ray or use of teratogenic medications.

Original Research Article
Pediatric Review: International Journal of Pediatric Research Available online at: www.medresearch.in 431|P a g e    Table 3. Results of Screening-2:Out of 29 "At risk" neonates who underwent second screening by OAE 86.2% (25) had "Pass" results in both ears, 6.9% (2) had "Refer" results in both ears , 3.4%(1) had "Refer" results only in right ear and 3.4%( 1) had "Refer" results only in left ear as shown in Table 4.  Results of the whole screening: A total of 75 "At risk" neonates were studied.29 neonates got referred in first screening. All these 29 neonates underwent second screening. 4 out of 29 "At risk" neonates got "Refer" results in second screening also. All these 4 "At risk" neonates underwent diagnostic test i.e. BERA. 2 of them had normal hearing sensitivity and 2 of them had confirmed hearing loss.  [7], incidence of hearing loss among all neonates screened was 0.56% (10/1769).
In a study done by Ohl c et al in France, 1461 "At risk" infants were screened, 4.55% were diagnosed as deaf or hard for hearing. The risk factors for sensorineural hearing loss were (in order of statistical significance): severe birth asphyxia; neurological disorder; syndromes known to be associated with hearing loss; TORCH (toxoplasmosis, rubella, cytomegalovirus, herpes) infections; family history of deafness; age at the time of screening; and the association of 2 or more risk factors [9].
In a study done by Van Riper et al, 2,103 "At risk" new-borns were screened, One hundred fourteen (5.4%) infants were diagnosed with bilateral hearing loss. 23 infants (1%) presented with unilateral hearing loss. 67 (49%) of the 137 infants diagnosed with hearing loss presented with greater than moderate hearing loss. 9 (13.4%) of these 67 patients presented with delayed onset hearing loss that was diagnosed at appointments subsequent to the initial screening. The largest percentage of diagnosed hearing loss was found in the "craniofacial anomalies" category [10] In a study done by Botelho  In the present study out of the 2 neonates who had hearing loss both of them had multiple risk factors and had bilateral hearing loss. One baby had 5 risk factors and other had 3 risk factors.

Conclusion
It can be safely concluded from the present study that hearing loss is more common in those babies with risk factors and there is a relationship between having risk factor (s) for hearing loss, not passing a hearing screen, and then later having a confirmed hearing loss. Major risk factors are NICU admission, Preterm, LBW, Ventilated babies, and jaundice.
This study has shown that two-stage TEOAE/DPOAE hearing screening can be successfully implemented as new-borns hearing screening method for early detection of hearing impaired, on a large scale, in a tertiary care hospital to achieve high-quality standard of screening programs. The finding is consistent with previous researches. As the incidence of hearing impairment in "At risk" new-borns is higher than the "no risk" newborns, Neonatal hearing screening of at least 'At risk' neonates is essential to detect large number of hearing impairment in the susceptible 'At risk 'new-borns population.

What this study adds to the existing knowledge?
Two-stage TEOAE/DPOAE hearing screening can be successfully implemented as new-borns hearing screening method. Hearing screening of at least 'At risk' neonates is essential to detect large number of hearing impairment.