Introduction

Hearing impairment is one of the most common birth defects in children. Hearing impairment in childhood significantly compromises a patient’s lingual, intellectual and social competence [1], and may lead to neurodevelopmental disorders [2]. Universal newborn hearing screening allows for early detection and intervention in cases of hearing impairment and thereby helps to alleviate physiological, psychological and social dysfunction [3]. In 2000, the Joint Committee on Infant Hearing proposed the overall objective of making a definite diagnosis at 3 months of age and implementing intervention at 6 months of age [4]. The process begins with the identification of hearing impairment and continues through screening, and the acquisition of satisfactory verbal communication skills that involve screening, diagnosis, intervention, rehabilitation education and follow-up [5]. Universal newborn hearing screening has been performed for 19 years in the Guangdong province, China. A screening-diagnosis-intervention system has gradually been instituted. Over the past decade, a relatively complete data management system has been established. In the present study, an etiological analysis of cases that failed the initial screening was performed, in which these cases were followed up for 4–10 years. The investigators sought to provide scientific evidence for government workers seeking to develop prevention and control plans and provide more precise guidance for families.

Methods

Study design

The present retrospective study included 10 years of follow-up (January 2005–December 2014) and was conducted at the Children’s Diagnostic Center for Hearing at the Third Affiliated Hospital of Sun Yat-Sen University in Guangdong, China. All data were obtained from the newborn hearing screening database established in 2005 by the hospital. This database also included the medical records for all follow-up examinations. All children diagnosed with bilateral hearing impairment after failing the initial screening were included in the present study. Disease progression was observed over 4–10 years of follow-up. Children, whose disabilities were diagnosed, were excluded from the present study. The study methodology was approved by the Ethics Committee at our institution.

Data collection

Two types of technology were used to screen for hearing impairment in newborns: otoacoustic emissions (OAEs) and the automatic auditory brainstem response (AABR) [6]. The device used to evaluate OAEs and AABR in the present study was the Madsen AccuScreen. For infants from Guangzhou city, hearing screenings were conducted with OAE and AABR. For infants from surrounding areas, the hearing screenings included OAE or AABR at a local hospital, followed by the combined use of OAE and AABR at our hospital [7]. The initial screening and rescreening were performed in a quiet room, with a noise level of < 45 dB. The degree of hearing loss was determined by calculating the average hearing threshold of both ears at air conductions of 0.5, 1.0, 2.0 and 4.0 kHz, with normal hearing at ≤ 25 dB HL. Mild hearing loss was 26–40 dB HL, moderate hearing loss was 41–70 dB HL, severe hearing loss was 71–90 dB HL and profound hearing loss was > 90 dB HL.

Infants born without any complications were typically screened for hearing loss within 3 days of birth. If an infant was in the Neonatal Intensive Care Unit, hearing screening, including OAE and AABR, was performed prior to the infant’s discharge from the hospital, or when the infant was in stable condition in an open crib.

Based on the consideration that amniotic fluid, mucus and fetal feces may cause occlusion of the external auditory canal of newborns and the timing of maternal postpartum reexamination [8], the guidelines for early hearing screening and intervention in newborns and infants require the rescreening to be performed within 42 days after birth. Objective hearing diagnostic results were generated by algorithms that considered the ABR versus subjective hearing thresholds. Sensorineural hearing loss with an average hearing threshold of > 40 dB HL in the better ear, as determined through audiological diagnosis, was defined as childhood hearing impairment [5, 9].

The external ear and tympanic membrane were examined for the diagnosis of newborns who had failed hearing screenings within 3 months of birth. It was necessary for the newborn to remain quiet for a long time to cooperate with the examination. Chloral hydrate (0.5 mL/kg) was orally administered for most newborns after parental consent. When necessary, luminal fluid (3–5 mg/kg) was intramuscularly injected to ensure that the children remained at rest for the full duration of the diagnostic test. The diagnostic tests included the following: distortion product otoacoustic emission; click-evoked auditory brainstem response; 40 Hz event-related potential with tone burst stimulation at 500, 1000 and 2000 Hz; tympanometry with 226-Hz and 1000-Hz probe tones; stimulation of the stapedius acoustic reflex at 500, 1000, 2000 and 4000 Hz. The diagnosis was considered to be definitive when the results of the diagnostic tests described above supported each other. The nature and degree of hearing loss were clearly determined. However, if the results of the above diagnostic tests conflicted, additional behavioral tests were performed. Children who were diagnosed with hearing impairment at 3 months of age were subjected to hearing diagnosis again at 6 months of age. If there was no improvement in hearing at 6 months of age, the intervention appropriate for each case was determined by the nature and degree of hearing loss. The patient’s data were reserved in the special database for hearing screening and diagnosis in newborns.

The criteria for the diagnosis of middle ear effusion were tympanic cavity effusion shown on the otological examination and characteristic findings on the acoustic impedance and ABR tests. In cases diagnosed with middle ear effusion, the tympanometry with a 226-Hz probe tone generated a type-B tympanogram, while the tympanometry with a 1000-Hz probe tone revealed no forward component and failed to elicit the stapedius acoustic reflex. For cases diagnosed with middle ear effusion, the ABR revealed prolonged I wave latency, with normal wave intervals and an elevated V-wave response threshold. For children with severe or profound sensorineural hearing loss in both ears, high-resolution computed tomography (CT) was performed to image the temporal bone after obtaining the consent of their parents. External, middle and inner ear malformations were diagnosed using a combination of abnormal findings on high-resolution temporal bone CT, otological examination and audiological diagnosis. For children diagnosed with retro-cochlear disease, a diagnosis of auditory neuropathy was made after the evaluation of magnetic resonance imaging (MRI) scans of the internal auditory canal to rule out space-occupying lesions and cochlear nerve abnormalities. A detailed maternal medical history was collected. Newborns who did not pass the hearing screening were evaluated for the presence of blood human cytomegalovirus (HCMV) and/or rubella virus within 2 weeks after birth. When the staining for HCMV-DNA was positive, HCMV infection was considered as the cause of deafness. For cases with rubella virus antibody IgM positive or an increased level of IgG antibody titers than the mother which did not fall within 3 months of birth, rubella virus infection was considered as the cause of deafness.

Deafness gene screening and the molecular diagnosis of deafness were introduced in 2012. The molecular diagnosis of deafness was recommended for newborns diagnosed with bilateral sensorineural hearing loss after 2012, and children who were still being followed up after their diagnosis in 2005. The efforts to screen for deafness genes were based on nine mutations on four genes for deafness commonly observed in Chinese people, with consideration of the cost, including GJB2 (35delG, 176del16, 235delC, 299delAT), SLC26A4 (2168A > G, IVS7-2A>G), mtDNA12srRNA (1494C>T, 1535A>G) and GJB3 (538 C>T). Children who were found to carry homozygous mutations or compound heterozygous mutations on the genes of interest received interventions and were closely followed up. If a single heterozygous mutation was identified through the process of the genetic screening, the exons of the mutated gene were sequenced. If the mutation was confirmed to be responsible for deafness, interventions were administered. When a mutation could not be confirmed, the parent was asked whether to proceed with the genetic diagnosis or follow-up. In the present study, genetic factors were considered to be responsible for deafness in the following cases: (1) the molecular etiology of hereditary deafness was clearly identified; (2) cases of bilateral sensorineural hearing loss, in which a single heterozygous mutation was identified with genetic screening; (3) cases of bilateral sensorineural hearing loss, in which no mutation was identified on the deafness gene screening, but existing a family history of hereditary deafness; (4) children with bilateral sensorineural hearing loss born to parents with consanguineous marriage. For children with bilateral sensorineural hearing loss, if there were no pregnancy- or birth-related causes, HCMV or rubella virus infections during pregnancy, family history of deafness, or parents refused to participate in the molecular diagnosis, the etiology of deafness was considered as unexplained.

After the first hearing diagnosis, a written note was given to parents to inform them of the results of the diagnostic testing, the recommended intervention and the follow-up schedule. The parents of all children diagnosed with hearing impairment were trained to perform auditory behavioral observations at home. If changes in hearing were found, the parents were instructed to seek out a timely hearing examination. For children with high risk for late-onset or progressive hearing loss, including those with a family history of deafness and a history of rubella virus and HCMV infection, staying in the intensive care unit for more than 5 days after birth and showing low birth weights [10, 11], their parents should seek out consultation in a timely fashion when any change in hearing is observed. If no change in hearing is noted, a reexamination should be performed once every 6 months before the age of three, and once a year between the age of 3 to 6 years old.

Statistical analysis

The statistical analysis was performed on the SPSS 20.0 using the Pearson χ2-test.

Results

The present study ultimately included 720 children: 369 children were born in our hospital and registered as Guangzhou residents, who failed both the initial screening and rescreening, respectively. Hearing impairment was confirmed in 51.25% of all children included in the study, and in 1.89/1000 of live births over the same period. A total of 351 children, accounting for 48.75% of the total, were from other cities in Guangdong province, failed the screening at local organizations, and were referred to our hospital for audiological and etiological diagnosis. Since the latter cohort of newborns were referred from different screening agencies, it was impossible to compute the number of live births over the same period. Therefore, the incidence of hearing impairment of any single etiology was not available. The children included in the study came from 21 prefecture-level cities in Guangdong province.

The 720 cases confirmed to have hearing impairment at the initial hearing diagnosis were divided into two groups: one group had a known etiology, while the other group had an unknown etiology. The known causes included genetic factors, secretory otitis media, rubella virus infection, inner ear malformation, HCMV infection, malformations of the middle ear ossicular chain and auditory neuropathy. The distribution of known etiologies is listed in Table 1. The percentages of deafness cases caused by genetic factors, secretory otitis media, rubella virus infection and auditory neuropathy, respectively, notably differed between the urban and surrounding rural areas. HCMV and rubella virus were detected in all neonates included in the present study. Among all 720 newborns, 452 newborns underwent CT, 13 newborns underwent MRI, and 405 newborns were screened for deafness genes and received a molecular diagnosis. The other cases with unexplained etiology included 116 newborns who underwent comprehensive testing and had negative results and 159 newborns whose parents had declined further evaluation.

Table 1 The etiological distribution in 720 children diagnosed with hearing loss at initial hearing diagnosis
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The causes of deafness among the 369 cases from Guangzhou and 351 cases from the surrounding areas were compared (Fig. 1).

Fig. 1
figure 1

The comparison between Guangzhou and the surrounding areas, in terms of the causes identified at the time when hearing loss was initially diagnosed. In Guangdong province, the genetic screening for neonatal deafness was first implemented in Guangzhou, and subsequently in the surrounding areas. Efforts to screen for genes related to neonatal deafness would increase the effectiveness over time as more data are collected

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Distribution of cases of hereditary deafness

Guangzhou and its surrounding areas have exhibited increased number of diagnosed cases of hereditary deafness since 2012, due to the introduction of deafness gene screening (Fig. 2).

Fig. 2
figure 2

The distribution of cases of hereditary deafness over the past 10 years. Over the past decade, the number of confirmed cases of hearing loss was higher in Guangzhou than in the surrounding areas. Guangzhou and the surrounding areas have exhibited significant growth since 2012

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After follow-up for 4–10 years

After 4–10 years of follow-up, 552 cases were diagnosed with childhood permanent hearing impairment (CPHI), accounting for 76.67% (552/720) of all cases of hearing loss. These changes occurred for the following reasons: (1) normal hearing was restored in 96 children with middle ear effusion; (2) in 22 children with suspicion of hearing deficit, this was finally excluded, and delayed auditory development was observed [12], including 19 cases from Guangzhou and three cases from the surrounding cities; (3) 35 cases were lost to follow-up, including 29 cases from the surrounding areas and six cases from Guangzhou; (4) 15 cases of middle ear ossicular chain malformation were still being followed-up. The changes in the causes of hearing impairment are listed in Table 2.

Table 2 Changes in causes of hearing impairment after 4–10 years follow-up
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The degree of CPHI in 552 confirmed cases (Fig. 3).

Fig. 3
figure 3

The prevalence of permanent childhood hearing impairment (552 confirmed cases). In the present study, moderate, severe and profound sensorineural hearing loss accounted for 41.34% (228/552), 26.8% (148/552) and 31.86% (176/552) of the total cases, respectively

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Discussion

Distribution of deafness causes identified at initial hearing diagnosis and analysis of deafness causes

The factors identified as causes of deafness clearly included hereditary deafness, secretory otitis media, maternal rubella virus infection during pregnancy, inner ear malformation, HCMV infection, middle ear ossicular chain malformation and auditory neuropathy [13].

Genetic factors

Genetic factors accounted for 30.56% of newborn hearing loss cases at initial diagnosis, which were similar to that reported by European and American researchers [14, 15]. Before deafness gene chips were applied in clinical settings, hereditary deafness was mainly identified by family history and consanguineous marriage. Since China’s family planning policy has been in effect for more than 30 years, most parents who gave birth in the past 10 years were the only child themselves. Therefore, relevant genetic clues are largely missing, leading to a very low diagnosis rate of hereditary deafness. The application of deafness gene chips in clinic since 2012 has identified some hereditary deafness cases without family history which has greatly improved the diagnosis rate of the causes of neonatal hearing impairment. However, the penetration of this technique still dramatically differs between urban and rural areas (Fig. 2).

However, a definite molecular cause is identified in only < 15% of deafness cases using presently available medical techniques under existing socio-economic conditions. A definite molecular cause is mainly pinpointed through screening deafness genes alone or in combination with exome sequencing for mutated genes. The main obstacles to the wider adoption of molecular diagnosis cover the following factors. Economically, exome sequencing or whole-genome sequencing is too expensive; technically, it is difficult to identify relationships between the massive mutation data generated from exome sequencing or whole-genome sequencing, and deafness phenotypes [16]. Sequencing is also time-consuming. At present, molecular diagnosis has little help to the choice of intervention for most cases of hereditary deafness, because hearing aids or cochlear implants are the only choices, depending on the degree of hearing loss, except for some auditory neuropathy patients. Some genes act as specific modifier variants in the genetic background, which perhaps, in combination with extrinsic factors, may have many complex outcomes for hard of hearing children [17]. In addition, there is still a long way to go before drug therapy or gene therapy can become a serious option.

Secretory otitis media

Physicians and families take some comfort that children with simple secretory otitis media associated with no oral or maxillofacial diseases (such as cleft palate) would restore their normal hearing at approximately 3 months after diagnosis through drug intervention or watchful waiting. Before hearing is recovered, children should be placed in a quiet environment, as much as possible. And their parents can increase the volume appropriately to effectively compensate for the effect of hearing loss on language development.

The third to fifth most common causes of deafness were rubella virus infection, inner ear malformations and HCMV infection. Deafness cases caused by such factors are often characterized by delayed and progressive sensorineural hearing loss and require close follow-up. However, such causes are often overlooked by pregnant women and clinicians, resulting in serious consequences, although they collectively account for the low percentage of total deafness cases.

Middle ear ossicular chain malformation

Since it often coexists with external ear malformation, it is easy to identify and diagnose. Furthermore, since external ear angioplasty is usually recommended at 6 years of age or older, this often causes serious psychological burden on children and parents before angioplasty, particularly for children complicated with external ear malformation. Moreover, external ear angioplasty is associated with an unsatisfactory outcome. Therefore, external ear malformation causes no less trouble to doctors and families than severe sensorineural hearing loss. Bone conduction hearing aids are recommended for children with aural atresia before the age of six. An ordinary hearing aid can be chosen if the shape and size of the external auditory canal are suitable. Middle ear hearing reconstruction surgery is often performed after 6 years of age.

Auditory neuropathy

Due to its distinctive audiological features, auditory neuropathy has garnered much attention during screening, diagnosis and intervention. Meanwhile, as its molecular etiology is increasingly clear, artificial cochlear implants can achieve satisfactory results, while synchronous auditory and visual stimuli are often given for other types of auditory neuropathies.

Sensorineural hearing loss of unknown etiology included the following cases. First, children may have hereditary deafness, but no family history of hereditary deafness was available. And the parents refused their children to take molecular genetic screening and diagnosis. There may be two reasons for their refusal: first, there is no better intervention for finding the gene in time. In addition, the present testing costs are all borne by the family. With the increasing adoption of deafness gene chips in clinic, they are expected to significantly improve the diagnosis rate of hereditary deafness. Second, HCMV infection is a major viral cause of intrauterine infection. More than 90% of congenitally infected children may be asymptomatic at birth. However, long-term sequelae can occur in 10–15% of cases, with sensorineural hearing loss being the most common. In addition, auditory developmental delay was noted in 22 cases. This cause was identified through close follow-up. Newborns with hearing retardation often present with the following three characteristics: (1) low birth weight, (2) premature birth and (3) no special reasons found. Therefore, if children present with improved hearing across different hearing diagnoses, the likelihood of auditory developmental delay should be seriously considered. It is noteworthy that up to 50% of cases with congenital infections have delayed hearing loss. Although this would not be detected through neonatal hearing screening, the hearing loss might be progressive [18]. Hence, the so-called “sensorineural hearing loss with unknown etiology” would occur in the future. Third, if it is still impossible to identify the cause using presently available diagnostic techniques, sensorineural hearing loss is considered to be caused by a truly unknown etiology. A more detailed etiological diagnosis should be performed by taking into account the above three aspects.

Comparison of causes of newborn hearing impairment between Guangzhou and its surrounding cities

The genetic screening of neonatal deafness in Guangdong Province was first implemented in Guangzhou and gradually radiated to the surrounding areas. The longer time since implementation of the screening for neonatal deafness genes in Guangzhou, the higher the acceptance of people. In addition, most of the hospitals carried out by Guangdong Province’s deafness genetic screening are tertiary hospital. The screening coverage rate is lower in economically underdeveloped areas and grassroots hospitals. Hence, the molecular diagnosis of deafness, which is a technique launched in recent years, has been much more accepted in Guangzhou than in its surrounding areas. Due to the spread of screening for deafness genes in Guangdong and more education about the importance of molecular diagnosis of deafness, this gap will be narrower in the future. Epidemiological differences are mainly due to the difference in acceptance and penetration of diagnostic techniques.

Infection-related deafness, including deafness caused by middle ear effusion, rubella virus infection and HCMV infection, was a lot more common in the surrounding areas, especially in rural areas, when compared to Guangzhou. The main reasons for these phenomena are that pregnant women in urban areas are much more aware of prenatal care than their rural counterparts and that education about proper feeding posture and pattern is also far more widespread in cities than in rural areas. This represents a key field that calls for major education, prevention and control efforts in the rural areas. The distribution of this condition does not significantly differ between Guangzhou and its surrounding areas. Auditory neuropathy was chiefly observed in the surrounding rural areas in the present study. Hence, further research is needed to investigate the underlying reasons.

Sensorineural hearing loss of unknown etiology

The incidence of this condition at the time of initial diagnosis did not notably differ between Guangzhou and its surrounding areas. However, after close follow-up and careful hearing diagnosis, delayed auditory development was diagnosed in 19 children from Guangzhou and three children from the surrounding cities. This marked difference resulted from the low rate of follow-up and inadequate observation of auditory behavior in areas surrounding Guangzhou.

Follow-up after the diagnosis of newborn hearing impairment

There were four common changes after the diagnosis of newborn hearing impairment: (1) the absorption and resolution of middle ear effusion; (2) the auditory developmental delay, which gradually improved and returned to normal as time progressed; (3) late-onset hearing impairment; (4) progressive hearing impairment. Children < 6 years old were unable to communicate clearly with physicians. Except for acute otitis media, which manifests as ear ache, fever and crying, most hearing disorders are asymptomatic and tend to be easily overlooked during the early stages. When children are found to have a speech disorder, they have missed the critical period of hearing and language development. Therefore, hearing follow-up is essential in childhood. Our follow-up program was as follows: for children with high-risk factors for late-onset or progressive hearing loss, parents were trained to observe hearing behaviors. If there was any change in hearing, these children were sent for reexamination. Children were reexamined once every 6 months before the age of 3 years old, and annually between the age of 3 and 6 years old. For children who passed the screening and those without risk factors for delayed hearing impairment, auditory behaviors were observed. Any change in hearing was confirmed during a follow-up examination. A total of 22 children with delayed auditory development were identified, and these children were helped to avoid unnecessary intervention. Furthermore, three cases of sensorineural hearing loss were progressively aggravated. Therefore, the amplification power of hearing aids in these patients was adjusted, to ensure the acquisition of robust verbal communication skills. Meanwhile, the follow-up conducted in the present study revealed that 96 cases of middle ear effusion identified at the initial diagnosis were resolved within 3 months. This offers strong evidence that the diagnostic results of newborn hearing tests should be shared with parents.

However, loss to follow-up after screening and diagnosis and poor observation of hearing behavior at home should not be overlooked. The problems of loss to follow-up were especially serious in the surrounding rural areas. The causes for loss to follow-up included the under-appreciation of the significance of newborn hearing screening, poor economic conditions, long journeys and ineffective transportation. Efforts should be made to strengthen science education in rural areas and improve public awareness of the significance and importance of hearing screening. It is necessary to perform screening for hearing impairment before children enters kindergarten and primary school, to ensure the early detection and early intervention for late-onset hearing impairment.

Permanent hearing impairment

In the present study, moderate, severe and profound sensorineural hearing loss accounted for 41.34% (228/552), 26.8% (148/552) and 31.86% (176/552), respectively, of the total cases. Children with moderate hearing loss respond to most auditory stimuli in daily life, which easily causes parents to under-appreciate the severity of this condition, and ignore early intervention. Eighteen children with moderate hearing loss did not receive any intervention, resulting in slurred speech, poor learning ability and social adaptability. For children with bilateral sensorineural hearing loss, bilateral intervention was given. Hearing aids were used in both ears, or a cochlear implant was used in one ear and a hearing aid in the other, depending on the degree of hearing loss. In the present study, 122 cases received only unilateral intervention, which affected the degree of success of the interventions. The reasons may be lack of relevant knowledge or lack of recognition on the part of parents, economic difficulties, or insufficient promotion of state aid policy about hearing aids and cochlear implants. For newborns with hearing impairment, it is also very necessary to determine whether the newborn will develop a mental disorder. Issues of language and communication contribute to the cause of psychiatric disturbance. The key to treatment is to teach parents to correctly treat their children’s deafness and psychological problems, although the provision of mental health services to deaf children remains controversial [19]. Children with profound or severe sensorineural deafness may also suffer from neurodevelopmental disorders. Children with sensorineural deafness frequently present a variety of disorders in different combinations. Clinicians and families predict results and adapt their expectations by understanding which disabilities are likely to co-occur with sensorineural hearing loss [2].

Future prevention and intervention strategies based on the present knowledge on the etiology of deafness

The etiological data obtained in the present study revealed that genetic factor-induced hearing loss is one of the major causes of neonatal hearing impairment. Previous studies have indicated that nearly 80% of hereditary deafness cases result from autosomal recessive inheritance [20]. Prenatal screening and prenatal diagnosis are rarely adopted and are only available in a few economically developed cities in China. Furthermore, the combined screening for hearing and deafness genes in newborns is the main stay of screening in China. The combined screening for hearing and deafness genes in newborns can determine whether newborns carry deafness genes, and allow for the “early detection, early diagnosis and early intervention”, to achieve the prevention of deafness. Efforts should be made to educate the public on related knowledge [21], train professionals in otology, audiology and genetics, and provide hereditary deafness counseling and birth guidance for families undergoing genetic screens for deafness. It is necessary to accelerate molecular epidemiological studies of hearing loss in different regions, to improve screening techniques, reduce screening costs, and enhance the coverage of mutation sites by genetic screening for deafness.

The incidence of infection-caused neonatal hearing impairment remains high in the surrounding areas, especially in rural areas. Efforts should be undertaken to strengthen education about preconception care and early pregnancy care and provide women of childbearing age with supplementary immunization against rubella virus, to minimize infection-caused hearing loss. Studies have shown that there may be complex interactions between congenital infections and genes. These data points to the prominent role of genetic background and environmental factors, or both, as modifiers of the severity of human hearing loss [18]. Hearing screening allows for early detection, early diagnosis and early intervention, and helps physicians to develop follow-up and rehabilitation programs for newborns who already have hearing impairment. In this manner, children can acquire good hearing and speech skills [22].

The thorough examination and long-term follow-up observations in the present study revealed the most common causes of hearing impairment among newborns. The city and its surrounding areas presented with different causes. Suggestions for prevention or treatment have been proposed. No additional genes or mutation sites were detected in children with hereditary hearing, suggesting possible omission. Polymerase chain reaction for CMV DNA from urine is the gold standard. The investigators intend to perform this test for all newborns who fail to pass the initial screening since it has high sensitivity and high specificity [23]. Future studies would be needed to compare the geographic areas studied.

In conclusion, long period follow-up is needed to detect delayed hearing impairment and auditory development in children, which should be taken into account when making an intervention strategy. More and more etiologies of neonatal hearing impairment would be disclosed in studies based on the use of the deafness gene chip. Tertiary prevention can be expected to protect against hereditary deafness on the basis of deafness gene screening and molecular diagnosis. Universal Newborn Hearing Screening programs have proven to be valuable and cost effective. New resources and efforts are required to achieve the complete standardization and informatization of the data [24].