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Prevalence and referral rates in neonatal hearing screening program using two step hearing screening protocol in Chennai – A prospective study
International Journal of Pediatric Otorhinolaryngology 79 (2015) 1745–1747
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Prevalence and referral rates in neonatal hearing screening program using two step hearing screening protocol in Chennai – A prospective study S.S. Vignesh a,*, V. Jaya a, B.I. Sasireka b, Kamala Sarathy a, M. Vanthana a a Institute of Speech and Hearing – Upgraded Institute of Otorhinolaryngology, Madras Medical College and Rajiv Gandhi Government General Hospital, EVR Periyar Salai, Chennai 3, India b Institute of Obstetrics and Gynecology, Government Hospital for Women and Children, Madras Medical College, Panpheon Road, Chennai 8, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 May 2015 Received in revised form 30 July 2015 Accepted 31 July 2015 Available online 8 August 2015
Objective: To estimate the prevalence and referral rates in well born and high risk babies using two step hearing screening protocol with Distortion Product Otoacoustic Emissions (DPOAE) and Automated Auditory Brainstem Response (AABR). Method: A prospective study was carried out on 1405 neonates (983 well born babies and 422 high risk babies) who were screened during May 2013 to January 2015 at Institute of Obstetrics and Gynecology, Madras Medical College, Chennai. All neonates were screened using two step screening protocol. They were initially tested with DPOAE. Referred babies in DPOAE were screened with AABR subsequently. Results: Among 1405 (100%) neonates 983 (69.96%) were well born babies and 422 (30.03%) were high risk babies. Total referral rate in DPOAE was found to be 311 (22.13%) among which 195 (13.87%) were well born babies and 116 (8.25%) were high risk babies. Out of 311 babies 31 (2.20%) babies were referred in AABR screening. In 31 babies referred in AABR 11(0.78%) were from well born group and 20 (1.42%) were from the high risk group. Further diagnostic evaluation of these babies, 2 (0.14%) were confirmed to have hearing loss. This study reveals, the prevalence of congenital hearing loss in our population is 1.42 per 1000 babies. Conclusion: Using two step protocol especially AABR along with DPOAE at the initial level of testing significantly reduces referral rates in new born screening programs. Also AABR decreases the false positive responses hence increasing the efficiency of screening program. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Hearing screening Referral rates Auditory Brainstem Response Two step protocol Otoacoustic emissions
1. Introduction Hearing Screening in developing countries with larger population is often challenging. New born hearing screening programs have been implemented over various institutions and hospitals across India [1]. Physiological tests like Evoked Otoacoustic emissions (EOAE) and Automated Auditory Brainstem Response (AABR) have been commonly used in new born hearing screening programs. Joint Committee for Infant Hearing (JCIH) positional statement in 2007 recommended both OAE and AABR to be
* Corresponding author. Tel.: +91 9789049622. E-mail addresses: [email protected] (S.S. Vignesh), [email protected] (V. Jaya), [email protected] (B.I. Sasireka), [email protected] (K. Sarathy), [email protected] (M. Vanthana). http://dx.doi.org/10.1016/j.ijporl.2015.07.043 0165-5876/ß 2015 Elsevier Ireland Ltd. All rights reserved.
included for high risk babies hearing screening protocol to identify neural hearing loss at initial level of screening [1]. There are several reports in literature that using double step screening protocols significantly reduces the referral rates in well born and high risk babies [2]. Using AABR in addition to EOAE decreases false negative and false positive referral rates significantly but incur higher cost [2,3]. Use of AABR alone or EOAE alone causes low sensitivity and specificity in high risk babies to identify neural hearing loss [4,5]. Also the prevalence of Auditory Neuropathy Spectrum disorder (ANSD) has been reported to be high in high risk babies [6]. In the Indian scenario, hearing disability is the second common disability after locomotor disability as per the National Sample Survey (2002) among rural and urban households [7]. Various programs namely National Programme for Prevention and Control of Deafness (NPPCD) in 2006 [8], and Rashtriya Bal Swasthya Karyakram (RBSK) in 2013 [9] initiated by the Government of India
1746
S.S. Vignesh et al. / International Journal of Pediatric Otorhinolaryngology 79 (2015) 1745–1747
are aiming at early identification, early intervention and reducing the total disease burden of hearing impairment and deafness. Hearing screening programs in India are often conducted in medical college hospitals and speech & hearing centers [10]. Only 63% of speech and hearing centers have been reported to use EOAE and AABR in hearing screening programs [10]. According to World Health Organization (WHO) report on new born and infant hearing screening; current issues and guiding principles for action in November 2009, Members of the International Association of Logopedics (IALP) Audiology Committee have recently reported on new born hearing screening program during 2008. The report states that in India protocol used in 1st and 2nd stage of hearing screening are Transient Evoked Otoacoustic Emissions (TEOAE) alone and AABR are used in 3rd stage of hearing screening [11]. DPOAE and AABR are rarely used in Indian scenario as a two step hearing screening protocol (screening with EOAE and AABR). In this context we carried out a prospective study in our hearing screening program using DPOAE and AABR. 2. Methods and materials 1405 neonates (723 males and 682 females) were screened during May 2013 to January 2015 to estimate the prevalence and compare the referral rates in well born as well as in high risk babies at Institute of Obstetrics and Gynecology, Madras Medical College, Chennai – a government organization. Prior to the study ethical committee approval was obtained from the local ethical committee at Madras Medical College. All neonates screened in the present study were in the age range of 2–28 days with the mean testing age of 8.78 days. Well born babies screened during this period were born through vaginal or cesarean delivery. High risk babies screened had any one high risk factor for hearing loss as reported by JCIH (2007). Well born babies were screened after 24 h of birth whereas high risk babies were screened before they were discharged from the hospital. All the mothers of the babies were counseled regarding the procedure of hearing screening and their benefits prior to testing. All the mothers of the neonates were provided information about study and its purpose. Also informed consent was obtained from the mothers before testing neonates. A two step screening protocol was used to screen babies. Neonates were tested with DPOAE followed by AABR testing if babies were referred in DPAOE testing at initial screening. Prior to DPOAE and AABR testing all the neonates underwent otoscopy examination to rule out vernix or debris in the external auditory meatus. 2.1. Instrumentation and test protocol All the babies were screened using Biologic AuDX pro (Natus Medical Inc., U.S.A.) DPOAE systems in a quiet room before they were discharged from the hospital. Prior to the study, the noise level of the rooms where the screening was carried was measured using Bruel & Kjer Type 2240 Sound level meter (Denmark). The rooms were located away from the NICU and well born wards. The noise levels in the testing rooms ranged from 40 dBA to 64 dBA measured during the testing. Initially stimulus level is calibrated in each ear according to manufacturer’s specifications. Later DPOAEs were recorded at frequencies of 5000 Hz, 4000 Hz, 3000 Hz, 2000 Hz and 1000 Hz for intensities of L1 65 dBSPL and L2 55 dBSPL. Signal to Noise Ratio (SNR) of 6 dB at any of the above three frequencies were considered as criteria for pass. All referred babies in DPOAE were retested with Echo Screen hearing screener (Natus Medical Inc., U.S.A.) AABR instrument. Auditory Brainstem Responses were recorded using 3 electrode placement (non inverting – forehead, inverting – mastoid and common – inion). AABR was recorded using click stimuli at
stimulus intensity of 30 dBnHL in the same test environment of DPOAE. All the testing was carried out when babies are well fed and quiet to reduce artifacts. Response detection either pass or refer was done by the AABR instrument using binomial template matching detection. Babies who were referred in AABR were followed up after 3 months for diagnostic hearing assessment. Diagnostic assessment was carried out using Behavioral observation Audiometry, Immitance audiometry, Diagnostic DPOAE and Auditory Brainstem Response audiometry using Inventis paino Plus channel audiometer (Inventis Audiology Equipment, Italy), GSI 39 Autotymp (Grason Stadler Inc., U.S.A.), IHS Smart EP systems (Intelligent Hearing Systems, U.S.A.) respectively. 3. Results 3.1. DPOAE referral rates Among 1405 (100%) neonates 983 (69.96%) were well born babies and 422 (30.04%) were high risk babies. In the initial testing with DPAOE 1094 (77.86%) babies were found to have passed DPOAE screening bilaterally. Total referral rate in DPOAE was found to be 311 (22.14%). Among well born and high risk babies, 195 (19.84%) in well born babies and 116 (27.49%) in high risk babies were referred during DPOAE testing. When unilateral and bilateral referral rates were considered in well born babies, DPOAE testing showed bilateral refer in 89 (9.05%) babies, right ear refer in 51(5.19%) babies and left ear refer in 55 (5.60%) babies. Whereas in high risk babies DPOAEs were bilaterally referred in 72 (17.06%) babies, right ear refer in 23 (5.45%) babies and left ear refer in 21 (4.98%) babies. Total number of neonates and its percentage of referral rates within well born and high risk group are shown in Table 1. 3.2. AABR referral rates AABR screening was done on 311 babies who were referred in DPOAE testing. Out of 311 babies 31 (9.97%) babies were referred in AABR screening which constitute 2.21% of total population. From 31 babies referred in AABR, 11 (1.11%) babies were from well born group and 20 (4.74%) babies were from the high risk group. Number and percentage of neonates referred in AABR screening across well born and high risk babies are tabulated in Table 2. 3.3. Diagnostic hearing assessment 31 babies who were referred in AABR underwent diagnostic hearing assessment using a complete audiological test battery. Table 1 Total number and percentage of neonates referred in DPOAE testing. Total babies referred, N = 311
Bilateral referral rate
Unilateral referral rate Right ear
Left ear
Well born babies – 195 (100%) High risk babies – 116 (100%)
89 (45.64%) 72 (62.06%)
51 (26.15%) 23 (19.82%)
55 (28.20%) 21 (18.10%)
Table 2 Total number and percentage of neonates referred in AABR testing. Total babies referred, N = 31
Bilateral referral rate
Unilateral referral rate Right ear
Left ear
Well born babies – 11 (100%) High risk babies – 20 (100%)
3 (27.27%) 8 (40%)
3 (27.27%) 5 (25%)
5 (45.45%) 7 (35%)
S.S. Vignesh et al. / International Journal of Pediatric Otorhinolaryngology 79 (2015) 1745–1747
Hearing thresholds estimation and site of lesion testing using physiological and electrophysiological tests were carried out. Out of 31 babies, 2 (6.45%) babies were confirmed to have bilateral hearing loss (>30 dBHL) which constitute 0.14% of total population. One of the babies had moderate conductive hearing loss and the other with severe to profound sensory neural hearing loss. Both the babies were from high risk group. First baby had Down’s syndrome who underwent Immitance audiometry and Bone conduction audiometry to confirm conductive hearing loss. Flat tympanogram was obtained in both ears using 1000 Hz probe tone and bone conduction ABR peaks were replicable till 30 dBnHL. Second baby had low birth weight, birth asphyxia, sepsis and was kept in NICU >5 days. This child showed normal 1000 Hz tympanogram, absent DPOAE and TEOAE and Click evoked ABR responses at 99 dBnHL. Estimated prevalence of congenital hearing loss in this current population is 1.42 per 1000 babies. 4. Discussion The prevalence of congenital bilateral hearing loss in the present study is comparable to the previous studies in India [14], as well as other countries [12,20]. Prevalence rate of congenital hearing loss is often reported to be from 1% or 2% [12,13] to 4% or 6% [14,15] per 1000 population. The estimated prevalence of hearing loss in the literature has been reported to be varying with the protocol used [2,4,5] degree of hearing loss, consideration of unilateral vs bilateral hearing loss [15], various types of hearing loss especially conductive, sensory, neural (auditory neuropathy spectrum disorders) [4,5] and late onset progressive hearing loss [15]. Although we considered unilateral, bilateral conductive and sensory neural hearing loss, we could only observe bilateral conductive and sensory type of hearing loss in the population considered. Referral rates in DPOAE in our population studied was 22.13% which is relatively higher when compared to the other studies. Various factors determine these referral rates in DPOAE especially the criterion level of SNR [16,17], 6 dB SNR considered in the present study could reduce the sensitivity and increase specificity of the results. Study by Barker et al. [17] report that with different criterion of SNR, false positive responses in DPOAE can vary from 11% to 35%. Also the test environment could have influenced these results varying the false positive responses of OAEs [23]. Since the sensitivity and specificity of DPOAE is generally the lesser than TEOAE [22] the referral rates are higher in our population. Two stage screening with DPOAE and AABR have been reported to increase sensitivity of new born hearing screening [18]. AABR used in the present study drastically reduced the referral rates from 22.13% to 2.20%. The referral rates of AABR in the study are comparable to the results of the other studies in the literature [2,19] which ranges from 1% to 3%. Referral rates in high risk babies were more than well born babies in both DPOAE and AABR testing as observed in other studies [4,16,24]. Recently studies comparing various protocols of hearing screening, report that using AABR alone can improve sensitivity and Specificity of newborn screening but incur high cost [2,3]. In developing countries like India, a two step screening protocol is feasible and easily carried out. Though this two step protocol miss out neural hearing loss such as auditory neuropathy spectrum disorders, it is sensitive to identify sensory neural and conductive hearing loss at early stage. 5. Conclusion Hearing loss is one of the major disabilities in India affecting speech and language development in children. Early identification of hearing loss and early intervention significantly improves speech
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and language development [21]. Two step hearing screening programs are rarely being carried out in India. The present study was carried out to analyze the prevalence and referral rates using two step hearing screening protocol. From the current study of neonatal hearing screening, we conclude that the prevalence of congenital hearing loss is 1.42%. Since identified babies were from high risk group we strongly recommend hearing screening of high risk neonates in developing countries. Also we emphasize that using AABR along with DPOAE significantly decreases the referral rates of newborn hearing screening in initial level of testing. References [1] Joint Committee on Infant Hearing, Year 2007 position statement of the Joint Committee on Infant Hearing: principles and guidelines for early hearing detection and intervention programs, Pediatrics 120 (2007) 898–921. [2] H.C. Lin, M.T. Shu, K.S. Lee, G.M. Ho, T.Y. Fu, S. Bruna, G. Lin, Comparison of hearing screening programs between one step with transient evoked otoacoustic emissions (TEOAE) and two steps with TEOAE and automated auditory brainstem response, Laryngoscope 115 (11) (2005) 1957–1962. [3] B.R. Vohr, W. Oh, E.J. Stewart, J.D. Bentkover, S. Gabbard, J. Lemons, L.A. Papile, R. Pye, Comparison of costs and referral rates of 3 universal newborn hearing screening protocols, J. Pediatr. 139 (2) (2001) 238–244. [4] A. Suppiej, E. Rizzardi, V. Zanardo, M. Franzoi, M. Ermani, E. Orzan, Reliability of hearing screening in high-risk neonates: comparative study of otoacoustic emission, automated and conventional auditory brainstem response, Clin. Neurophysiol. 118 (4) (2007) 869–876. [5] R. Dhawan, N.N. Mathur, Comparative evaluation of Transient Evoked Oto-acoustic Emissions and Brainstem Evoked Response Audiometry as screening modality for hearing impairment in neonates, Indian J. Otolaryngol. Head Neck Surg. 59 (1) (2007) 15–18. [6] P.A. Rea, W.P.R. Gibson, Evidence for surviving outer hair cell function in congenitally deaf ears, Laryngoscope 113 (2003) 230–234. [7] National Sample Survey Organization, Disabled Persons in India, NSS 58th Round. Report no. 485 (58/26/1), National Sample Survey Organization, Ministry of Statistics and Programme Implementation, Government of India, New Delhi, 2003. [8] Directorate General of Health Services, National Programme for Prevention and Control of Deafness, Project Proposal, Ministry of Health and Family Welfare, New Delhi, 2006. [9] Rastriya Bal Swasthya Karyakram (RBSK), Operational Guidelines, 2013 Available from http://www.unicef.org/india/7._Rastriya_Bal_Swaasthya_karyakaram.pdf. [10] S. Kumar, B. Mohapatra, Status of newborn hearing screening program in India, Int. J. Pediatr. Otorhinolaryngol. 75 (1) (2011) 20–26. [11] Newborn and infant hearing screening, Current issues and guiding principles for action outcome of a WHO informal consultation held at who headquartersGeneva, Switzerland, November 09–10, 2009, Available from http://www.who.int/ blindness/publications/Newborn_and_Infant_Hearing_Screening_Report.pdf. [12] J.S. Oliveira, L.B. Rodrigues, F.S. Aure´lio, V.B. Silva, Risk factors and prevalence of newborn hearing loss in a private health care system of Porto Velho, Northern Brazil, Rev. Paul Pediatr. 31 (3) (2013) 299–305. [13] B.A. Prieve, F. Stevens, The New York State Universal Newborn Hearing Screening Demonstration Project: introduction and overview, Ear Hear. 21 (2000) 85–91. [14] P.V. John Jewel, Varghese, Tejinder Singh, Ashish Varghese., Newborn hearing screening – experience at a tertiary hospital in Northwest India, Int. J. Otolaryngol. Head Neck Surg. 2 (2013) 211–214. [15] K.R. White, K. Munoz, Screening, Semin. Hear. 29 (2) (2008) 149–158. [16] J.A. Salata, J.T. Jacobson, B. Strasnick, Distortion-product otoacoustic emissions hearing screening in high-risk newborns, Otolaryngol. Head Neck Surg. 118 (1) (1998) 37–43. [17] S.E. Barker, M.M. Lesperance, P.R. Kileny, Outcome of newborn hearing screening by ABR compared with four different DPOAE pass criteria, Am. J. Audiol. 9 (2) (2000) 142–148. [18] Z.M. Xu, J. Li, T.Z. Hu, J.H. Sun, X.M. Shen, Sensitivity of distortion product otoacoustic emissions and auditory brain-stem response in neonatal hearing screening, a comparative study, Zhonghua Yi Xue Za Zhi 83 (4) (2003) 278–280. [19] H.C. Lin, M.T. Shu, K.S. Lee, H.Y. Lin, G. Lin, Reducing false positives in newborn hearing screening program: how and why, Otol. Neurotol. 28 (6) (2007) 788–792. [20] J.S. Oliveira, L.B. Rodrigues, F.S. Aure´lio, V.B. Silva, Risk factors and prevalence of newborn hearing loss in a private health care system of Porto Velho, North. Brazil. Rev. Paul. Pediatr. 31 (3) (2013) 299–305. [21] C. Yoshinaga-Itano, A.L. Sedey, D.K. Coulter, A.L. Mehl, Language of early- and later-identified children with hearing loss, Pediatrics 102 (5) (1998) 1161–1171. [22] T. Janssen, A review of the effectiveness of otoacoustic emissions for evaluating hearing status after newborn screening, Otol. Neurotol. 34 (6) (2013) 1058–1063. [23] B.O. Olusanya, Ambient noise levels and infant hearing screening programs in developing countries: an observational report, Int. J. Audiol. 49 (8) (2010) 535–541. [24] K. Wroblewska-Seniuk, K. Chojnacka, B. Pucher, J. Szczapa, J. Gadzinowski, M. Grzegorowski, The results of newborn hearing screening by means of transient evoked otoacoustic emissions, Int. J. Pediatr. Otorhinolaryngol. 69 (10) (2005) 1351–1357.
Contents lists available at ScienceDirect
International Journal of Pediatric Otorhinolaryngology journal homepage: www.elsevier.com/locate/ijporl
Prevalence and referral rates in neonatal hearing screening program using two step hearing screening protocol in Chennai – A prospective study S.S. Vignesh a,*, V. Jaya a, B.I. Sasireka b, Kamala Sarathy a, M. Vanthana a a Institute of Speech and Hearing – Upgraded Institute of Otorhinolaryngology, Madras Medical College and Rajiv Gandhi Government General Hospital, EVR Periyar Salai, Chennai 3, India b Institute of Obstetrics and Gynecology, Government Hospital for Women and Children, Madras Medical College, Panpheon Road, Chennai 8, India
A R T I C L E I N F O
A B S T R A C T
Article history: Received 12 May 2015 Received in revised form 30 July 2015 Accepted 31 July 2015 Available online 8 August 2015
Objective: To estimate the prevalence and referral rates in well born and high risk babies using two step hearing screening protocol with Distortion Product Otoacoustic Emissions (DPOAE) and Automated Auditory Brainstem Response (AABR). Method: A prospective study was carried out on 1405 neonates (983 well born babies and 422 high risk babies) who were screened during May 2013 to January 2015 at Institute of Obstetrics and Gynecology, Madras Medical College, Chennai. All neonates were screened using two step screening protocol. They were initially tested with DPOAE. Referred babies in DPOAE were screened with AABR subsequently. Results: Among 1405 (100%) neonates 983 (69.96%) were well born babies and 422 (30.03%) were high risk babies. Total referral rate in DPOAE was found to be 311 (22.13%) among which 195 (13.87%) were well born babies and 116 (8.25%) were high risk babies. Out of 311 babies 31 (2.20%) babies were referred in AABR screening. In 31 babies referred in AABR 11(0.78%) were from well born group and 20 (1.42%) were from the high risk group. Further diagnostic evaluation of these babies, 2 (0.14%) were confirmed to have hearing loss. This study reveals, the prevalence of congenital hearing loss in our population is 1.42 per 1000 babies. Conclusion: Using two step protocol especially AABR along with DPOAE at the initial level of testing significantly reduces referral rates in new born screening programs. Also AABR decreases the false positive responses hence increasing the efficiency of screening program. ß 2015 Elsevier Ireland Ltd. All rights reserved.
Keywords: Hearing screening Referral rates Auditory Brainstem Response Two step protocol Otoacoustic emissions
1. Introduction Hearing Screening in developing countries with larger population is often challenging. New born hearing screening programs have been implemented over various institutions and hospitals across India [1]. Physiological tests like Evoked Otoacoustic emissions (EOAE) and Automated Auditory Brainstem Response (AABR) have been commonly used in new born hearing screening programs. Joint Committee for Infant Hearing (JCIH) positional statement in 2007 recommended both OAE and AABR to be
* Corresponding author. Tel.: +91 9789049622. E-mail addresses: [email protected] (S.S. Vignesh), [email protected] (V. Jaya), [email protected] (B.I. Sasireka), [email protected] (K. Sarathy), [email protected] (M. Vanthana). http://dx.doi.org/10.1016/j.ijporl.2015.07.043 0165-5876/ß 2015 Elsevier Ireland Ltd. All rights reserved.
included for high risk babies hearing screening protocol to identify neural hearing loss at initial level of screening [1]. There are several reports in literature that using double step screening protocols significantly reduces the referral rates in well born and high risk babies [2]. Using AABR in addition to EOAE decreases false negative and false positive referral rates significantly but incur higher cost [2,3]. Use of AABR alone or EOAE alone causes low sensitivity and specificity in high risk babies to identify neural hearing loss [4,5]. Also the prevalence of Auditory Neuropathy Spectrum disorder (ANSD) has been reported to be high in high risk babies [6]. In the Indian scenario, hearing disability is the second common disability after locomotor disability as per the National Sample Survey (2002) among rural and urban households [7]. Various programs namely National Programme for Prevention and Control of Deafness (NPPCD) in 2006 [8], and Rashtriya Bal Swasthya Karyakram (RBSK) in 2013 [9] initiated by the Government of India
1746
S.S. Vignesh et al. / International Journal of Pediatric Otorhinolaryngology 79 (2015) 1745–1747
are aiming at early identification, early intervention and reducing the total disease burden of hearing impairment and deafness. Hearing screening programs in India are often conducted in medical college hospitals and speech & hearing centers [10]. Only 63% of speech and hearing centers have been reported to use EOAE and AABR in hearing screening programs [10]. According to World Health Organization (WHO) report on new born and infant hearing screening; current issues and guiding principles for action in November 2009, Members of the International Association of Logopedics (IALP) Audiology Committee have recently reported on new born hearing screening program during 2008. The report states that in India protocol used in 1st and 2nd stage of hearing screening are Transient Evoked Otoacoustic Emissions (TEOAE) alone and AABR are used in 3rd stage of hearing screening [11]. DPOAE and AABR are rarely used in Indian scenario as a two step hearing screening protocol (screening with EOAE and AABR). In this context we carried out a prospective study in our hearing screening program using DPOAE and AABR. 2. Methods and materials 1405 neonates (723 males and 682 females) were screened during May 2013 to January 2015 to estimate the prevalence and compare the referral rates in well born as well as in high risk babies at Institute of Obstetrics and Gynecology, Madras Medical College, Chennai – a government organization. Prior to the study ethical committee approval was obtained from the local ethical committee at Madras Medical College. All neonates screened in the present study were in the age range of 2–28 days with the mean testing age of 8.78 days. Well born babies screened during this period were born through vaginal or cesarean delivery. High risk babies screened had any one high risk factor for hearing loss as reported by JCIH (2007). Well born babies were screened after 24 h of birth whereas high risk babies were screened before they were discharged from the hospital. All the mothers of the babies were counseled regarding the procedure of hearing screening and their benefits prior to testing. All the mothers of the neonates were provided information about study and its purpose. Also informed consent was obtained from the mothers before testing neonates. A two step screening protocol was used to screen babies. Neonates were tested with DPOAE followed by AABR testing if babies were referred in DPAOE testing at initial screening. Prior to DPOAE and AABR testing all the neonates underwent otoscopy examination to rule out vernix or debris in the external auditory meatus. 2.1. Instrumentation and test protocol All the babies were screened using Biologic AuDX pro (Natus Medical Inc., U.S.A.) DPOAE systems in a quiet room before they were discharged from the hospital. Prior to the study, the noise level of the rooms where the screening was carried was measured using Bruel & Kjer Type 2240 Sound level meter (Denmark). The rooms were located away from the NICU and well born wards. The noise levels in the testing rooms ranged from 40 dBA to 64 dBA measured during the testing. Initially stimulus level is calibrated in each ear according to manufacturer’s specifications. Later DPOAEs were recorded at frequencies of 5000 Hz, 4000 Hz, 3000 Hz, 2000 Hz and 1000 Hz for intensities of L1 65 dBSPL and L2 55 dBSPL. Signal to Noise Ratio (SNR) of 6 dB at any of the above three frequencies were considered as criteria for pass. All referred babies in DPOAE were retested with Echo Screen hearing screener (Natus Medical Inc., U.S.A.) AABR instrument. Auditory Brainstem Responses were recorded using 3 electrode placement (non inverting – forehead, inverting – mastoid and common – inion). AABR was recorded using click stimuli at
stimulus intensity of 30 dBnHL in the same test environment of DPOAE. All the testing was carried out when babies are well fed and quiet to reduce artifacts. Response detection either pass or refer was done by the AABR instrument using binomial template matching detection. Babies who were referred in AABR were followed up after 3 months for diagnostic hearing assessment. Diagnostic assessment was carried out using Behavioral observation Audiometry, Immitance audiometry, Diagnostic DPOAE and Auditory Brainstem Response audiometry using Inventis paino Plus channel audiometer (Inventis Audiology Equipment, Italy), GSI 39 Autotymp (Grason Stadler Inc., U.S.A.), IHS Smart EP systems (Intelligent Hearing Systems, U.S.A.) respectively. 3. Results 3.1. DPOAE referral rates Among 1405 (100%) neonates 983 (69.96%) were well born babies and 422 (30.04%) were high risk babies. In the initial testing with DPAOE 1094 (77.86%) babies were found to have passed DPOAE screening bilaterally. Total referral rate in DPOAE was found to be 311 (22.14%). Among well born and high risk babies, 195 (19.84%) in well born babies and 116 (27.49%) in high risk babies were referred during DPOAE testing. When unilateral and bilateral referral rates were considered in well born babies, DPOAE testing showed bilateral refer in 89 (9.05%) babies, right ear refer in 51(5.19%) babies and left ear refer in 55 (5.60%) babies. Whereas in high risk babies DPOAEs were bilaterally referred in 72 (17.06%) babies, right ear refer in 23 (5.45%) babies and left ear refer in 21 (4.98%) babies. Total number of neonates and its percentage of referral rates within well born and high risk group are shown in Table 1. 3.2. AABR referral rates AABR screening was done on 311 babies who were referred in DPOAE testing. Out of 311 babies 31 (9.97%) babies were referred in AABR screening which constitute 2.21% of total population. From 31 babies referred in AABR, 11 (1.11%) babies were from well born group and 20 (4.74%) babies were from the high risk group. Number and percentage of neonates referred in AABR screening across well born and high risk babies are tabulated in Table 2. 3.3. Diagnostic hearing assessment 31 babies who were referred in AABR underwent diagnostic hearing assessment using a complete audiological test battery. Table 1 Total number and percentage of neonates referred in DPOAE testing. Total babies referred, N = 311
Bilateral referral rate
Unilateral referral rate Right ear
Left ear
Well born babies – 195 (100%) High risk babies – 116 (100%)
89 (45.64%) 72 (62.06%)
51 (26.15%) 23 (19.82%)
55 (28.20%) 21 (18.10%)
Table 2 Total number and percentage of neonates referred in AABR testing. Total babies referred, N = 31
Bilateral referral rate
Unilateral referral rate Right ear
Left ear
Well born babies – 11 (100%) High risk babies – 20 (100%)
3 (27.27%) 8 (40%)
3 (27.27%) 5 (25%)
5 (45.45%) 7 (35%)
S.S. Vignesh et al. / International Journal of Pediatric Otorhinolaryngology 79 (2015) 1745–1747
Hearing thresholds estimation and site of lesion testing using physiological and electrophysiological tests were carried out. Out of 31 babies, 2 (6.45%) babies were confirmed to have bilateral hearing loss (>30 dBHL) which constitute 0.14% of total population. One of the babies had moderate conductive hearing loss and the other with severe to profound sensory neural hearing loss. Both the babies were from high risk group. First baby had Down’s syndrome who underwent Immitance audiometry and Bone conduction audiometry to confirm conductive hearing loss. Flat tympanogram was obtained in both ears using 1000 Hz probe tone and bone conduction ABR peaks were replicable till 30 dBnHL. Second baby had low birth weight, birth asphyxia, sepsis and was kept in NICU >5 days. This child showed normal 1000 Hz tympanogram, absent DPOAE and TEOAE and Click evoked ABR responses at 99 dBnHL. Estimated prevalence of congenital hearing loss in this current population is 1.42 per 1000 babies. 4. Discussion The prevalence of congenital bilateral hearing loss in the present study is comparable to the previous studies in India [14], as well as other countries [12,20]. Prevalence rate of congenital hearing loss is often reported to be from 1% or 2% [12,13] to 4% or 6% [14,15] per 1000 population. The estimated prevalence of hearing loss in the literature has been reported to be varying with the protocol used [2,4,5] degree of hearing loss, consideration of unilateral vs bilateral hearing loss [15], various types of hearing loss especially conductive, sensory, neural (auditory neuropathy spectrum disorders) [4,5] and late onset progressive hearing loss [15]. Although we considered unilateral, bilateral conductive and sensory neural hearing loss, we could only observe bilateral conductive and sensory type of hearing loss in the population considered. Referral rates in DPOAE in our population studied was 22.13% which is relatively higher when compared to the other studies. Various factors determine these referral rates in DPOAE especially the criterion level of SNR [16,17], 6 dB SNR considered in the present study could reduce the sensitivity and increase specificity of the results. Study by Barker et al. [17] report that with different criterion of SNR, false positive responses in DPOAE can vary from 11% to 35%. Also the test environment could have influenced these results varying the false positive responses of OAEs [23]. Since the sensitivity and specificity of DPOAE is generally the lesser than TEOAE [22] the referral rates are higher in our population. Two stage screening with DPOAE and AABR have been reported to increase sensitivity of new born hearing screening [18]. AABR used in the present study drastically reduced the referral rates from 22.13% to 2.20%. The referral rates of AABR in the study are comparable to the results of the other studies in the literature [2,19] which ranges from 1% to 3%. Referral rates in high risk babies were more than well born babies in both DPOAE and AABR testing as observed in other studies [4,16,24]. Recently studies comparing various protocols of hearing screening, report that using AABR alone can improve sensitivity and Specificity of newborn screening but incur high cost [2,3]. In developing countries like India, a two step screening protocol is feasible and easily carried out. Though this two step protocol miss out neural hearing loss such as auditory neuropathy spectrum disorders, it is sensitive to identify sensory neural and conductive hearing loss at early stage. 5. Conclusion Hearing loss is one of the major disabilities in India affecting speech and language development in children. Early identification of hearing loss and early intervention significantly improves speech
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and language development [21]. Two step hearing screening programs are rarely being carried out in India. The present study was carried out to analyze the prevalence and referral rates using two step hearing screening protocol. From the current study of neonatal hearing screening, we conclude that the prevalence of congenital hearing loss is 1.42%. Since identified babies were from high risk group we strongly recommend hearing screening of high risk neonates in developing countries. Also we emphasize that using AABR along with DPOAE significantly decreases the referral rates of newborn hearing screening in initial level of testing. References [1] Joint Committee on Infant Hearing, Year 2007 position statement of the Joint Committee on Infant Hearing: principles and guidelines for early hearing detection and intervention programs, Pediatrics 120 (2007) 898–921. [2] H.C. Lin, M.T. Shu, K.S. Lee, G.M. Ho, T.Y. Fu, S. Bruna, G. 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