Hearing loss is a disability that can affect individuals at any age. According to the World Health Organization (WHO) in its World Report on Hearing, nearly 2.5 billion people are expected to experience hearing loss by 2050, with at least 700 million needing rehabilitation services. Currently, 430 million people, primarily those with moderate or higher grades of hearing loss who would benefit the most from rehabilitation, are affected [1]. The majority of these individuals reside in low- and middle-income countries, where access to ear and hearing care (EHC) is often limited. [1] About 25% of hearing loss cases can occur in newborns to toddlers. The primary cause of hearing loss in newborns is congenital abnormalities, affecting four to six out of every 1000 live births in developing countries and two out of every 1000 live births in developed countries. [2] Hearing function is crucial for intellectual and social development in childhood, and any disturbance can affect a child's personal and social well-being. Families often notice a child's hearing loss when they begin speaking later than their peers. [3] If detected too late, the challenges become more significant. Hearing loss from birth can lead to difficulties in speech, language, cognitive, and academic development. [4] As hearing impairment is a hidden disability, it is usually detected after 2 years of birth when the child starts speaking, by which time there is irreversible stunting of the language development potential. Many developed countries have well-established newborn hearing screening programs. Considering infrastructure limitations in India, it is crucial to adopt a cost-effective method for detecting hearing loss. The usefulness of newborn hearing screening for its effectiveness in early identification has previously been well-proven. [5, 6] Otoacoustic emissions (OAE) and Brainstem Evoked Response Audiometry (BERA) tests are used to screen newborns for hearing loss.

OAE is known to be cost-effective, quick, simple, and reliable with 100% sensitivity and 99% specificity [7] while compared to OAE, BERA has the additional advantage of identifying newborns with auditory neuropathy. The other advantage of BERA is its high sensitivity and specificity [8]. The goal of newborn hearing screening is to identify moderate to severe permanent, bilateral congenital hearing loss, with an average threshold of 30–40 dB or higher in the frequency range crucial for speech recognition (500–4000 Hz). Based on studies from various countries, the prevalence ranges from 0.5/1000 to 5/1000 infants with congenital and early onset hearing impairment. [9-11] At least 90 percent of infants with hearing loss live in unindustrialized countries. [12] In India, among the screened newborns for hearing loss, there is an incidence of 1 to 6 per 1000. [13, 14] Among the children with hearing loss, 50% were missed only because of screening high-risk neonates [15, 16]. Hence, a cost-effective universal screening program is the best option to sustain and detect early. The earlier hearing loss is detected, the earlier intervention can begin, which increases the likelihood of optimizing a child’s potential across developmental areas. Hence the present study was conducted for early identification of neonatal hearing impairment using OAE and BERA.

This prospective observational study was conducted in the Department of Pediatrics in coordination with the Department of ENT and District Early Intervention Center (DEIC), Government Medical College, Nalgonda.  The study was carried out over a period of 12 months from November 2022 to October 2023. Institutional Ethical approval was obtained for the study. Written consent was obtained from the parents of the infants involved in the study after explaining the nature of the study in vernacular language. The study subjects included all neonates born and inborn admitted to the NICU of Government General Hospital attached to Government Medical College, Nalgonda, during the study period.

Sample Size:

Based on the Gupta S et al. [17] on universal hearing screening in newborns using otoacoustic emissions and brainstem evoked response the rate of refer on first OAE screening was taken at 10%

So, for the present study, the estimated prevalence of OAE was taken at 10%

Estimated prevalence (p) = 10%

Confidence interval (CI) = 95%

Relative precision (l) = 20% of p = 10 × 20 = 2

Using the standard formula for proportion = [(Zα/2)2 × p × q] / l2

Sample size (n) = (Zα/2)2 × p × (1-p) / l2 = (1.96×1.96) × 10 × 90 / 2 x 2

= 3456/ 4 = 864

Taking an additional 15% of cases, the final sample size for the present study was rounded to 1000 newborns.

Inclusion Criteria

1. Neonates born and inborn are admitted to the NICU of Government General Hospital.
2. Babies whose parents gave written consent for the test and study.
3. Babies who required NICU management were included after their stabilization and before getting discharged from the hospital.

Exclusion Criteria

1. Congenital anomalies of the external ear.
2. Active ear infections.
3. Hearing loss due to middle and external ear conditions.

Method of Collection of Data: All the babies were inspected routinely in the pinna external ear and post-aural region. Occluding wax and debris were removed by cleaning with a swab and a tympanic membrane examination was done by using a heine 3000 series otoscope with plastic speculum. Using a pretested and validated questionnaire, potential risk factors were identified. Both the normal and high-risk neonates underwent hearing assessment.

Audiological Testing:

A three-stage hearing screening protocol with TEOAE (Transient Evoked Otoacoustic Emissions) testing for stages one and two and BERA, which is the gold standard test for hearing assessment for babies, was conducted for stage three.

Stage 1: All babies born and inborn admitted to NICU were screened for hearing loss by TEOAE testing by an audiologist. The test was carried out in a quiet room in the Audiometry Lab using a TEOAE machine. The babies were tested in supine position, preferably i0n the guardian's lap, and preferably when the child is asleep. The first level of screening was done from 24 hours of birth to 7 days of birth by using Oto Acoustic Emission. The TEOAE equipment that was used was calibrated and tested for hearing at 4 frequencies i.e. 500, 1000, 2000, and 4000 Hz. The results were given as either ''PASS'' or ''REFER''. ''PASS'' suggests that the newborn has no hearing impairment in the specific frequency tested. The absence of emissions for two out of the four frequencies was considered as ''REFER''. Evoked TEOAE is absent when hearing loss is more than 30–35 dB SPL (Sound Pressure Level) which is indicated as ''REFER''.

Stage 2: Babies who failed the initial test are subjected to repeat TEOAE testing after ENT examination during the follow-up in a soundproof room; in the Audiology Department. Babies who failed the second test are subjected to stage 3 testing.

Stage 3: Those who failed the TEOAE test were subjected to BERA as soon as possible to confirm the hearing loss. The BERA result was interpreted as normal or hearing loss (HL). In the case of newborns with normal BERA, parents were advised to bring their babies back for further evaluation in case they notice any delay in speech development.

Statistical analysis:

Data collected was entered into MS Excel 2013 spreadsheet. The collected data was analyzed using the IBM Statistical Package for Social Sciences (IBM SPSS) version 23 software. Continuous variables were reported as mean ± standard deviation (SD) while categorical variables were expressed as absolute values and percentages. Microsoft Excel 2013 was used for generating charts and diagrams. The chi-square test was applied to find the significant factors causing hearing loss and a P-value less than 0.05 was considered statistically significant.

This study was done on a population of 1,000 newborns who were screened on Stage 1: Initial OAE Screening Test: Otoacoustic Emissions (OAE) Outcomes: Pass: 929 newborns (92.9%) Refer for Stage 2: 71 newborns (7.1%).  Stage 2: Repeat OAE Testing Test: Second OAE for referred cases Outcomes: Pass: 49 newborns (69.0% of Stage 2 cohort) Refer for Stage 3: 22 newborns (31.0% of Stage 2 cohort). Stage 3: Diagnostic BERA Testing Test: Brainstem Evoked Response Audiometry (BERA) Sample: 22 newborns referred from Stage 2. Outcomes: Normal Hearing: 16 newborns (72.7% of Stage 3 cohort) Confirmed Hearing Impairment: 6 newborns (27.3% of Stage 3 cohort) given in Table 1

Among the 1000 newborns initially screened for hearing loss using OAE, 71 (7.1%) failed the first-stage screening. Of those, 22 failed the second-stage OAE, and 6 were confirmed to have hearing loss via BERA in the third stage, giving a prevalence of 6 per 1000 newborns (Table 2). In the study population, 514 (51.4%) were male and 507 (50.7%) were delivered via LSCS. Preterm births (gestational age <37 weeks) constituted 108 (10.8%) of the population, and 148 (14.8%) had low birth weight (<2.5 kg). Birth asphyxia occurred in 56 (5.6%) newborns, hyperbilirubinemia in 54 (5.4%), family history of deafness in 31 (3.1%), and congenital infections in 12 (1.2%).

OAE Referral Rates and Associated Risk Factors are depicted in Table 3. The overall OAE referral rate was higher among newborns with specific risk factors. Preterm birth: 11 out of 108 preterm babies (10.2%) had OAE referrals compared to term babies, showing a statistically significant association (p < 0.001). Low birth weight: 12 of 148 (8.1%) low birth weight newborns were referred (p < 0.001). Birth asphyxia: 7 of 56 (12.5%) with asphyxia failed OAE (p < 0.002). Hyperbilirubinemia: 9 of 54 (16.7%) had OAE referral (p < 0.001).

                                *Significant

BERA-confirmed hearing loss was significantly associated with several risk factors (Table 4) as Preterm birth in 4 of 108 (3.7%) had hearing loss (OR: 18.5, p < 0.001). Low birth weight in 4 of 148 (2.7%) had hearing loss (OR: 12.2, p = 0.001). Birth asphyxia in 4 of 56 (7.1%) had hearing loss (OR: 35.4, p < 0.001). Family history of deafness in 5 of 31 (16.1%) had hearing loss (OR: 184.6, p < 0.001). Congenital infections in 4 of 12 (33.3%) had hearing loss (OR: 228.0, p < 0.001). Ototoxic drugs in 4 of 6 (66.7%) had hearing loss (OR: 996.0, p < 0.001). No statistically significant association was found between hearing loss and gender (male: 0.8%, female: 0.4%), residential area (urban: 0.6%, rural: 0.5%), or mode of delivery (LSCS: 1%, NVD: 0.2%).

        * Significant

Multivariate Analysis of Predictors (Table 5) shows the independent predictor of hearing loss was a family history of deafness with an adjusted Odds Ratio (OR) of 42.3 (p < 0.001). Congenital infections had an adjusted OR of 28.9 (p = 0.001), Hyperbilirubinemia: showed an adjusted OR of 9.6 (p = 0.013), and Gestational age <37 weeks showed an adjusted OR of 5.2 (p = 0.038)

                                 * Significant

Screening Performance Metrics (Table 6) showed a sensitivity of (6/6)100%, Specificity of (977/994) 98.3%, False positive rate of 1.7% (16/22) and Positive predictive value of 27.3% (6/22).

Untreated congenital hearing loss can significantly affect a child’s language acquisition, as well as cognitive development, educational outcomes, and social integration. Universal Newborn Hearing Screening (UNHS) is a vital public health strategy that has a role in early detection of hearing loss and initiating timely intervention. Early diagnosis of hearing loss becomes more efficient by the UNHS method which supports better language and cognitive development in children.  This prospective observational study involving 1,000 newborns was done at the Department of Pediatrics and District Early Intervention Centre (DEIC) at Government Medical College, Nalgonda during the period from November 2022 to October 2023. Hearing screening was performed using Otoacoustic Emissions (OAE) and Brainstem Evoked Response Audiometry (BERA) for those who failed the initial tests. The prevalence of hearing loss was found to be 6 per 1,000 newborns in this study. The results of our study are in agreement with studies by Singh et al. [18] (6.7/1000) and Jewel et al. [19] (4/1000). However, it is higher as compared to the study of Gupta et al. [17] (2.2/1000) and Dedhia et al. [20] (0.88%). In contrast, Akinpelu et al. [21] (31/1000), Gulati et al. [22] (37/1000) among preterm infants, and Nagal et al. [23] (77/1000) in sick neonates which have a higher prevalence as compared to our study. In the current study, we found that 10.8% of infants were preterm, 14.8% had low birth weight, 1.7% required mechanical ventilation, 3.1% needed prolonged NICU care, and 5.4% had hyperbilirubinemia requiring treatment. These findings were in concordance with Gupta et al. [17] and Dedhia et al. [20]. OAE was used in two screening stages and showed no significant difference in referral rates based on gender, residential status, or mode of delivery, consistent with Singh et al. [18]. The results of our study are consistent with the findings of Satish HS et al. [24], Gulati et al. [22], and Nagal et al. [23].  However, we found a significant association was observed between hearing loss and several risk factors which included Infants <37 weeks had a 3.7% prevalence of hearing loss, significantly higher than term infants (0.2%). The second was low birth weight 2.7% of LBW infants had hearing loss vs. 0.2% in normal-weight infants. Another important factor was birth asphyxia 7.1% of asphyxiated infants had hearing loss, significantly higher than non-asphyxiated ones (0.2%). Infants with hyperbilirubinemia had a significantly higher rate of hearing loss (7.4%) compared to those without (0.2%). The other factor analyzed was family history which showed that 16.1% of infants with a family history of hearing loss were affected, compared to 0.1% without such history. The congenital infections showed that 33.3% of infected newborns had hearing loss. We also found that with ototoxic medications 66.7% of exposed infants had hearing loss, consistent with Rechia et al. [25] Mechanical Ventilation & NICU Stay of >5 days showed significant associations with hearing loss, aligning with findings from Rechia et al. [25], Nagal et al. [23], and Dedhia et al. [20].

Research by Gulati et al. [22] supports the finding that infants with hearing loss typically have multiple risk factors along with diagnosis data. Results from the bivariate analysis showed preterm birth, LBW, asphyxia, hyperbilirubinemia, family history, congenital infections, and ototoxic drug exposure together with prolonged NICU stay acted as significant risk factors. Multiple investigations have confirmed LBW, asphyxia, and exchange transfusions as risk factors based on the findings reported by Jewel et al. [19] Gupta et al. [17], and Singh et al. [18]. Therefore, our research demonstrates how early diagnosis of hearing loss depends on UNHS and emphasizes which neonatal risk factors need additional monitoring attention. Screening procedures combined with immediate actions for high-risk babies deliver essential outcomes for their development.

The screening protocol with an objective test, that is, Transient Evoked Otoacoustic Emission (TEOAE) and confirmation by Brainstem Evoked Response Audiometry, is a very useful tool for early identification and early intervention of congenital hearing loss in newborns, which prevents further disability of speech, language, and auditory memory. Hence, the results of this study can be used to initiate universal newborn hearing screening in other hospitals. Moreover, this study highlights the relevance of neonatal hearing screening in other states of India and countries where this screening is not performed routinely in all hospitals, creating awareness to identify neonatal risk factors associated with hearing loss, and understanding the importance of early identification and intervention among health care professionals. In addition, neonatal hearing screening of only the at-risk population is likely to miss some cases of hearing loss. Hence, we recommend the introduction of universal neonatal hearing in all tertiary-level hospitals.

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