Identification of neonatal hearing impairment: transient evoked otoacoustic emissions during the perinatal period

Revisiting the transient-evoked otoacoustic emissions passing criteria used for newborn hearing screening

OBJECTIVE

To assess transient-evoked otoacoustic emissions (TEOAE) data from 15 years of a newborn hearing screening program and evaluate how well various criteria separate ears with and without hearing loss.

DESIGN

Retrospective review of TEOAE data using logistic regression, receiver operating characteristic curves, and cumulative percentage graphs.Study sample: Children with hearing loss who passed TEOAE screening as a newborn were compared to children who failed TEOAE screening and normal hearing children who either passed or failed. Exclusions were applied for acquired hearing loss or auditory neuropathy.

RESULTS

Ears with hearing loss that passed screening had significantly lower TEOAE response levels compared to ears with normal hearing. Noise levels, test times, and number of sweeps were also lower. Most of these ears had mild hearing loss. Logistic regression results showed that high-frequency TEOAE response level is the best predictor of hearing loss. A multivariate "logit" score calculated from the regression was the best indicator for separating ears with hearing loss from ears with normal hearing.

CONCLUSIONS

TEOAE response levels or an algorithm which incorporates logit scores should be considered as a minimum passing criterion to increase the sensitivity of the TEOAE screening.

Analysis of audiological outcomes of children referred from a universal newborn hearing screening program over 9 years in Beijing, China

Universal newborn hearing screening (UNHS) and audiological diagnosis are crucial for children with congenital hearing loss (HL). The objective of this study was to analyze hearing screening techniques, audiological outcomes and risk factors among children referred from a UNHS program in Beijing. A retrospective analysis was performed in children who were referred to our hospital after failing UNHS during a 9-year period. A series of audiological diagnostic tests were administered to each case, to confirm and determine the type and degree of HL. Risk factors for HL were collected. Of 1839 cases, 53.0% were referred after only transient evoked otoacoustic emission (TEOAE) testing, 46.1% were screened by a combination of TEOAE and automatic auditory brainstem response (AABR) testing, and 1.0% were referred after only AABR testing. HL was confirmed in 55.7% of cases. Ears with screening results that led to referral experienced a more severe degree of HL than those with results that passed. Risk factors for HL were identified in 113 (6.1%) cases. The main risk factors included craniofacial anomalies (2.7%), length of stay in the neonatal intensive care unit longer than 5 days (2.4%) and birth weight less than 1500 g (0.8%). The statistical data showed that age (P < 0.001) and risk factors, including craniofacial anomalies (P < 0.001) and low birth weight (P = 0.048), were associated with the presence of HL. This study suggested that hearing screening plays an important role in the early detection of HL and that children with risk factors should be closely monitored.

[Clinical protocol: audiological assessment of infants in Russian Federation. Part I]

The clinical protocol of audiological assessment in infants was prepared by the workgroup of Russian pediatric audiologists from different regions. The goal of the protocol is unification approaches to audiological diagnosis of the infants. The protocol has been developed according the evidence based medicine principles, by reviewing current scientific publications on the topic and taking into account the order of providing medical services and other clinical practice guidelines. When direct evidence was not available, both indirect evidence and consensus practice were considered in making recommendations. This guideline is not intended to serve as a standard to dictate precisely how the child should be diagnosed. This guideline is meant to provide the evidence base from which the clinician can make individualized decisions for each patient. The first part of the protocol covers following sections: equipment, staff requirements, timing of the diagnostics, case history and risk factors, preparing the child for the appointment, sedation and general anesthesia, otoscopy, tympanometry and acoustic reflex, otoacoustic emissions, skin preparing, electrode montage, choosing the stimulators, auditory brainstem responses on broadband and narrow-band stimuli, on bone conducted stimuli, auditory steady-state responses, masking, combined correction factors.

Reliability of Serological Prestin Levels in Humans and its Relation to Otoacoustic Emissions, a Functional Measure of Outer Hair Cells

OBJECTIVES

Serological biomarkers, common to many areas of medicine, have the potential to inform on the health of the human body and to give early warning of risk of compromised function or illness before symptoms are experienced. Serological measurement of prestin, a motor protein uniquely produced and expressed in outer hair cells, has recently been identified as a potential biomarker to inform on the health of the cochlea. Before any test can be introduced into the clinical toolkit, the reproducibility of the measurement when repeated in the same subject must be considered. The primary objective of this study is to outline the test-retest reliability estimates and normative ranges for serological prestin in healthy young adults with normal hearing. In addition, we examine the relation between serum prestin levels and otoacoustic emissions (OAEs) to compare this OHC-specific protein to the most common measure of OHC function currently used in hearing assessments.

DESIGN

We measured prestin levels serologically from circulating blood in 34 young adults (18 to 24 years old) with clinically normal pure-tone audiometric averages at five different timepoints up to six months apart (average intervals between measurements ranged from <1 week to 7 weeks apart). To guide future studies of clinical populations, we present the standard error of the measurement, reference normative values, and multiple measures of reliability. Additionally, we measured transient evoked OAEs at the same five timepoints and used correlation coefficients to examine the relation between OAEs and prestin levels (pg/mL).

RESULTS

Serum prestin levels demonstrated good to excellent reliability between and across the five different time points, with correlation coefficients and intraclass correlations >0.8. Across sessions, the average serum prestin level was 250.20 pg/mL, with a standard error of measurement of 7.28 pg/mL. Moreover, positive correlations (generally weak to moderate) were found between prestin levels and OAE magnitudes and signal-to-noise ratios.

CONCLUSIONS

Findings characterize serum prestin in healthy young adults with normal hearing and provide initial normative data that may be critical to interpreting results from individuals with sensorineural hearing loss. Our results demonstrate reliability of serum prestin levels in a sample of normal-hearing young adults across five test sessions up to 6 months apart, paving the way for testing larger samples to more accurately estimate test-retest standards for clinical protocols, including those involving serial monitoring. The positive correlations between serum prestin and OAE levels, although weak to moderate, reinforce that the source of serum prestin is likely the outer hair cells in the inner ear, but also that serum prestin and OAEs each may also index aspects of biologic function not common to the other.

Transient Otoacoustic Emissions and Auditory Brainstem Responses in Low-Risk Cohort of Newborn and One-Month-Old Infants: Assessment of Infant Auditory System Physiology in the Prenatal Alcohol in SIDS and Stillbirth Network Safe Passage Study

BACKGROUND

The Prenatal Alcohol and Sudden Infant Death Syndrome and Stillbirth Network, known as the "Safe Passage Study," enrolled approximately 12,000 pregnant women from the United States and South Africa and followed the development of their babies through pregnancy and the infant's first year of life to investigate the role of prenatal alcohol exposure in the risk for sudden infant death syndrome (SIDS) and adverse pregnancy outcomes, such as stillbirth and fetal alcohol spectrum disorders.

PURPOSE

Auditory system tests were included in the physiologic test battery used to study the effects of prenatal alcohol exposure on neurophysiology and neurodevelopment, as well as potential causal relationships between neurodevelopmental disorders and SIDS and/or stillbirth. The purpose of this manuscript is to describe normative results when using the auditory test battery applied.

RESEARCH DESIGN

The test battery included the auditory brainstem response (ABR) and transient-evoked otoacoustic emissions (TEOAEs). Data were collected on individual ears of newborns and 1-month-old infants.

STUDY SAMPLE

From a cohort of 6,070 with auditory system exams, a normative subsample of 325 infants were selected who were not exposed prenatally to alcohol, cigarette smoke, or drugs nor were they preterm or low birthweight. The subsample is small relative to the overall study because of strict criteria for no exposure to substances known to be associated with SIDS or stillbirth and the exclusion of preterm and low birthweight infants. Expectant mothers were recruited from general maternity at two comprehensive clinical sites, in the northern plains in the United States and in Cape Town, South Africa. These populations were selected for study because both were known to be at high-risk for SIDS and stillbirth.

DATA COLLECTION AND ANALYSIS

ABR and TEOAE recordings were stored electronically. Peak latency and amplitude analysis of ABRs were determined by study personnel, and results were evaluated for differences by age, sex, test site, race, and ear (left versus right).

RESULTS

TEOAE findings were consistent with existing literature including the increase in signal-to-noise (SNR) over the first month of life. The SNR increase is due to an increase in amplitude of the emission. TEOAE amplitude asymmetry favoring the right ear was found, whereas SNR asymmetry was not, perhaps because of the small sample size. A nonsignificant trend toward larger responses in female babies was found; a result that is generally statistically significant in studies with larger samples. Latencies were found to be shorter in ABRs elicited in the right ear with amplitudes that were slightly bigger on average. An expected decrease in wave V latency was observed from birth to 1-month of age, but the finding was of borderline significance (p = 0.058).

CONCLUSIONS

One month is a short time to judge development of the auditory system; however, the ABR and TEOAE findings were consistent with current literature. We conclude that the auditory system data acquired for the Safe Passage Study, as reflected in the data obtained from this cohort of "unexposed" infants, is consistent with published reports of these auditory system measures in the general population.

Normative Wideband Acoustic Immittance Measurements in Caucasian and Aboriginal Children

Purpose The aims of this study were to develop normative data for wideband acoustic immittance (WAI) measures in Caucasian and Australian Aboriginal children and compare absorbance measured at 0 daPa (WBA0) and tympanometric peak pressure (TPP; WBATPP) between the 2 groups of children. Additional WAI measures included resonance frequency, equivalent ear canal volume, TPP, admittance magnitude (YM), and phase angle (YA). Method A total of 171 ears from 171 Caucasian children and 87 ears from 87 Aboriginal children who passed a test battery consisting of 226-Hz tympanometry, transient evoked otoacoustic emissions, and pure tone audiometry were included in the study. WAI measures were obtained under pressurized conditions using wideband tympanometry. Data for WBA0, WBATPP, YM, and YA were averaged in one-third octave frequencies from 0.25 to 8 kHz. Results There was no significant ear effect on all of the 7 measures for both groups of children. Similarly, there was no significant gender effect on all measures except for WBATPP in Aboriginal children. Aboriginal boys had significantly higher WBATPP than girls at 1.5 and 2 kHz. A significant effect of ethnicity was also noted for WBATPP at 3, 4, and 8 kHz, with Caucasian children demonstrating higher WBATPP than Aboriginal children. However, the effect size and observed power of the analyses were small for both effects. Conclusion This study developed normative data for 7 WAI measures, namely, WBA0, WBATPP, TPP, Veq, RF, YM, and YA, for Caucasian and Aboriginal children. In view of the high similarity of the normative data between Caucasian and Aboriginal children, it was concluded that separate ethnic-specific norms are not required for diagnostic purposes.

Effects of changes in click-evoked otoacoustic emission (CEOAE) pass criteria, as used in the English newborn hearing screening program, on screening outcome

OBJECTIVE

There were two objectives, firstly what effect does a change in the pass criteria of a click-evoked otoacoustic emission (CEOAE) newborn hearing screen have on the number of cases of significant hearing impairment detected by follow up diagnostics, and secondly how does this change affect the screen pass rate?

DESIGN

Changes in the pass criteria were: reduction in the signal-to-noise ratio (SNR); reduction in the minimum signal level (MSL); inclusion of the 1-kHz half-octave band; reduction from two to a single half-octave band.

STUDY SAMPLE

Data from three screening sites was used within the English newborn hearing screening program from the period 2002 to 2006, with a total number of births of about 40,000. There were 42 bilateral and 43 unilateral cases of significant hearing impairment.

RESULTS

No effect on the number of cases detected by follow up diagnostics was observed when: (1) SNR was reduced to a minimum of 5 dB; (2) MSL was reduced to -10 dB SPL; and (3) the 1-kHz band was included. With all these changes the percentage pass rate improved by 0.36%.

CONCLUSIONS

The current choice of SNR and MSL criteria appears robust. Only a small increase in pass rate is possible without affecting case detection.

Down syndrome: an electrophysiological and radiological profile

OBJECTIVES/HYPOTHESIS

To assess the hearing status of trisomy 21 patients by analyzing electrophysiological and radiological findings of any correlation between hearing impairment and major or minor inner ear malformations.

STUDY DESIGN

Prospective radiological and electrophysiological study.

METHODS

A group of 34 ears of Down syndrome subjects and 20 ears of a volunteer age- and sex-matched control group of 10 normal subjects were studied electrophysiologically by means of otoacoustic emissions and auditory brainstem response. Temporal bone computed tomography (CT) scans were carried out in both groups; radiological findings were compared. Inner ear structure measurements were applied attempting to disclose subtle bony labyrinthine anomalies. The findings from both groups were statistically analyzed employing the t test.

RESULTS

The rate of sensorineural hearing loss (SNHL) in Down syndrome group was 41%. Temporal bone CT scans showed no ossicular malformation in all Down syndrome cases. Major inner ear abnormalities were disclosed in 5.8%; they corresponded to two cases of lateral semicircular canal dysplasia detected on CT images by visual inspection. The application of various inner ear structure measurements increased the overall detection rate of common inner ear malformations to 47%. A statistically significant correlation was found between hearing level and vestibule length (P = .009) and internal auditory canal length (P = .028). Vestibular aqueduct width was correlated to different otic abnormalities.

CONCLUSIONS

SNHL is mainly secondary to the underestimated subtle inner ear malformations that are adequately demonstrated by adopting standardized inner ear structure measurements on petrous bone imaging. Vestibular height and internal auditory canal length were correlated to SNHL.

LEVEL OF EVIDENCE

3b.

Targeted versus Universal Neonatal Hearing Screening in a Single Egyptian Center

Aim. To compare targeted neonatal hearing screening (TNHS) and universal neonatal hearing screening (UNHS) since many developing countries, including Egypt, implement selective screening for high-risk neonates. Methods. 150 neonates were assessed; 50 full terms consecutively admitted to the well-baby nursery and 100 neonates consecutively admitted to neonatal intensive care unit (NICU), Ain Shams University. Patients were further subdivided into high-risk group which included 50 neonates with multiple risk factors for hearing loss and low risk group which included 50 neonates with only one risk factor. Transient evoked otoacoustic emissions (TEOAEs) were used for hearing screening. Auditory brain response (ABR) was performed 3 months later for failed TEOAEs. Results. The most frequent risk factor was consanguinity (46%). In the well-baby population, 16% failed TEOAEs. In the NICU, 30% of the low risk and 38% of the high risk groups failed TEOAEs. Regarding ABR, failed results were 12%, 10%, and 8% in the high-risk, low-risk, and healthy groups, respectively. Conclusion. The use of TNHS would have missed 8% of neonates from the well-baby group who actually had PCHL (permanent congenital hearing loss). The use of UNHS would identify all cases with PCHL, allowing for early intervention and follow-up.

Assessment of the feasibility and coverage of a modified universal hearing screening protocol for use with newborn babies of migrant workers in Beijing

BACKGROUND

Although migrant workers account for the majority of newborns in Beijing, their children are less likely to undergo appropriate universal newborn hearing screening/rescreening (UNHS) than newborns of local non-migrant residents. We hypothesised that this was at least in part due to the inadequacy of the UNHS protocol currently employed for newborn babies, and therefore aimed to modify the protocol to specifically reflect the needs of the migrant population.

METHODS

A total of 10,983 healthy babies born to migrant mothers between January 2007 and December 2009 at a Beijing public hospital were investigated for hearing abnormalities according to a modified UNHS protocol. This incorporated two additional/optional otoacoustic emissions (OAE) tests at 24-48 hours and 2 months after birth. Infants not passing a screening test were referred to the next test, until any hearing loss was confirmed by the auditory brainstem response (ABR) test.

RESULTS

A total of 98.91% (10983/11104) of all newborn children underwent the initial OAE test, of which 27.22% (2990/10983) failed the test. 1712 of the failed babies underwent the second inpatient OAE test, with739 failing again; thus significantly decreasing the overall positive rate for abnormal hearing from 27.22% to 18.36% ([2990-973 /10983)]; p = 0). Overall, 1147(56.87%) babies underwent the outpatient OAE test again after1-month, of whom 228 failed and were referred for the second outpatient OAE test (i.e. 2.08% (228/10983) referral rate at 1month of age). 141 of these infants underwent the referral test, of whom 103 (73.05%) tested positive again and were referred for a final ABR test for hearing loss (i.e. final referral rate of 1.73% ([228-38/10983] at 2 months of age). Only 54 infants attended the ABR test and 35 (0.32% of the original cohort tested) were diagnosed with abnormal hearing.

CONCLUSIONS

Our study shows that it is feasible and practical to achieve high coverage rates for screening hearing loss and decrease the referral rates in newborn babies of migrant workers, using a modification of the currently employed UNHS protocol.

High frequency tympanometry findings in neonates: does it depend on head position?

OBJECTIVE

The purpose of this study was to investigate the effect of head positions on high frequency tympanometry (HFT) results obtained from neonates.

DESIGN

A cross-sectional study to compare HFT results obtained from neonates in two head positions (face sideways and face up).

STUDY SAMPLE

One hundred and fifty-seven neonates (80 female, 77 male; mean age = 48.3 ± 26.7 hours) participated.

RESULTS

The mean uncompensated admittance at 200 daPa obtained in the face sideways position was significantly greater than that obtained in the face up position (1.02 versus 0.96 mmho). A significant ear effect for baseline compensated admittance was found (right/left = 0.64/0.53 mmho). However, there were no significant main effects for head positions for the tympanometric peak pressure, baseline compensated static admittance, and component compensated static admittance measures, indicating that these measures are resilient to head positions.

CONCLUSION

These findings support the use of HFT normative values regardless of the two head positions investigated in the present study.

The influence of the type of breastfeeding on middle ear conditions in infants

Infants should be submitted to hearing screening upon birth, and for the results to be complete, it is necessary to assess middle ear conditions.

OBJECTIVE

To check whether the type of breastfeeding in infants between zero and four months can impact middle ear conditions my means an ENT assessment and acoustic immittance comparing neonates who were submitted to hearing screening with those who failed it.

MATERIALS AND METHODS

Otoacoustic emissions (OAE) was carried out in 60 infants between zero and four months. They were distributed in two groups; group I had the infants with OAE and those infants in group II did not have OAE. They were submitted to tympanometry with a 1000 Hz test tone and ENT assessment.

RESULTS

Bottle fed infants or those who were fed in a mixed way had more changes to their audiometry and ENT assessment, with a statistically significant difference. The breastfed infants had a higher occasion of normal tympanometries and normal otorhinolaryngological assessment, with statistically significant difference.

CONCLUSION

We then concluded that those breastfed implants had less ENT changes and as well as less acoustic immittance change, thus enabling OAEs. Breastfeeding alone can be considered a protection factor against middle ear changes.

Changes in transient-evoked otoacoustic emissions in the first month of life

OBJECTIVE

Current Joint Committee on Infant Hearing guidelines recommend the use of transient-evoked otoacoustic emissions (TEOAEs) as a screening tool to identify hearing loss for newborns cared for in the well-baby nursery. Newborns who do not pass the TEOAE screen before leaving the hospital are typically rescreened as outpatients by 1 mo of age, at which time, approximately 50 to 70% pass screening criteria. To better understand why many infants are referred at initial screening but pass at the rescreening, more complete knowledge of developmental differences in the TEOAE levels, noise floor, or a combination of both for infants who pass and fail birth screening is needed. In addition, it has been shown that infants with occluding ear-canal debris are more likely to not pass TEOAE screening at the hospital than those without occluding ear-canal debris. This study explores whether changes in TEOAE levels in half-octave frequency bands are related to changes in ear-canal debris over the first month of life.

DESIGN

Seventy-nine neonates from a well-baby nursery had their hearing screened before leaving the hospital and again at approximately 1 mo of age. All participants passed the follow-up screening. Overall TEOAE levels and levels in half-octave frequency bands centered at 1.5, 2, 3, and 4 kHz were measured. Judgments of ear-canal debris were made by otoscopy and were rated using one of three categories at both visits.

RESULTS

TEOAE levels in infants significantly increased from birth to 1 mo of age across all frequencies tested, regardless of whether they passed or failed the screening at birth. The increase in TEOAE level was frequency dependent, with the greatest increases occurring in the highest frequency bands. No significant correlation between debris change and frequency-specific changes was found for either ear. Infants who failed the screening at birth but who subsequently passed at 1 mo of age had significantly lower TEOAE levels at the rescreening than did infants with passing TEOAE levels at birth. However, pass/fail status at birth was only a weak predictor of TEOAE levels at 1 mo of age.

CONCLUSIONS

The increase in TEOAE levels during the first month of life is frequency dependent, with greater increases occurring at higher frequencies. Increased TEOAE levels were not associated with changes in ear-canal debris.

Test-retest reliability of the acoustic stapedial reflex test in healthy neonates

OBJECTIVE

The acoustic stapedial reflex (ASR) test has been shown to provide useful information about the function of the auditory system. However, the reliability of this test when applied to healthy neonates has not been systematically studied. This study aimed to evaluate the test-retest reliability of the ASR test in newborn babies shortly after birth.

DESIGN

Using a cross-sectional design, 219 healthy neonates, aged between 24 and 192 hr, who passed an automated auditory brain stem response screening test, were recruited and assessed using transient-evoked otoacoustic emissions (TEOAEs), high-frequency (1000 Hz) tympanometry, and ASR tests. One randomly selected ear from each neonate was tested. ASRs were elicited by presenting a 2 kHz pure tone and broadband noise (BBN) separately to the test ear in an ipsilateral stimulation mode using a Madsen Otoflex diagnostic immittance meter. A total of 194 (86/108 males/females; 115/79 left/right) ears, which met a set of inclusion criteria, were included in the test-retest reliability analysis for the 2-kHz tone stimulus. In addition, 123 (62/61 males/females; 77/46 left/right) ears were included in the test-retest reliability analysis for the BBN stimulus. The ASR threshold (ASRT) for each stimulus was measured. The ASR procedure was then repeated to acquire retest data.

RESULTS

Ipsilateral ASRs were elicited in 91.3% (200/219) of neonates, whereas the remaining 8.7% (19/219) exhibited flat tympanograms (no identifiable peak) and absent reflexes with a "refer" outcome in the TEOAE test. The mean ASRT (76.2 dB HL averaged over 194 ears) for the 2 kHz pure tone was higher than that for the BBN (64.9 dB HL averaged over 123 ears). The findings, based on the results of an analysis of variance with repeated measure, showed that the ASRTs for the retest condition did not differ significantly from those of the first test for both stimuli (p > 0.05). The ASR test also showed high test-retest reliability as demonstrated by intracorrelation coefficients across the test-retest conditions of 0.83 for the 2 kHz pure tone and 0.76 for the BBN stimulus.

CONCLUSION

This study demonstrated that ASRs could be consistently elicited from healthy neonates who showed a single-peaked configuration in the high-frequency tympanometry test and passed the automated auditory brain stem response and TEOAE tests. The findings showed that the ASRTs did not vary significantly across the test-retest conditions, and the high intracorrelation coefficients illustrate the reliability of the ASR test. Given the high test-retest reliability, the ASR test holds promise as a useful diagnostic/screening instrument in ascertaining the hearing status in neonates.

Infant hearing loss and connexin testing in a diverse population

PURPOSE

Previous studies of connexin-related hearing loss have typically reported on mixed age groups or adults. To further address epidemiology and natural history of connexin-related hearing loss, we conducted a longitudinal study in an ethnically diverse cohort of infants and toddlers under 3 years of age. Our study compares infants with and without connexin-related hearing loss to examine differences in the prevalence of connexin and non-connexin-related hearing loss by ethnic origin, detection by newborn hearing screening, phenotype, neonatal risk factors, and family history. This is the first study to differentiate infants with and without connexin-related hearing loss.

METHODS

We enrolled 95 infants with hearing loss from whom both exons of Cx26 were sequenced and the Cx30 deletion was assayed. Demographic, family history, newborn hearing screening data, perinatal, and audiologic records were analyzed.

RESULTS

Genetic testing identified biallelic Cx26/30 hearing loss-associated variants in 24.7% of infants with a significantly lower prevalence in Hispanic infants (9.1%). Eighty-two infants underwent newborn hearing screening; 12 infants passed, 3 had connexin-related hearing loss. No differences in newborn hearing screening pass rate, neonatal complications, or hearing loss severity were detected between infants with and without connexin-related hearing loss. Family history correlates with connexin-related hearing loss.

CONCLUSIONS

Connexin-related hearing loss occurs in one quarter of infants in an ethnically diverse hearing loss population but with a lower prevalence in Hispanic infants. Not all infants with connexin-related hearing loss fail newborn hearing screening. Family history correlates significantly with connexin-related hearing loss. Genetic testing should not be deferred because of newborn complications. These results will have an impact on genetic testing for infant hearing loss.

Tone burst-evoked otoacoustic emissions in neonates: normative data

BACKGROUND

Tone-burst otoacoustic emissions (TBOAEs) have not been routinely studied in pediatric populations, although tone burst stimuli have greater frequency specificity compared with click sound stimuli. The present study aimed (1) to determine an appropriate stimulus level for neonatal TBOAE measurements when the stimulus center frequency was 1 kHz, (2) to explore the characteristics of 1 kHz TBOAEs in a neonatal population.

METHODS

A total of 395 normal neonates (745 ears) were recruited. The study consisted of two parts, reflecting the two study aims. Part I included 40 normal neonatal ears, and TBOAE measurement was performed at five stimulus levels in the range 60-80 dB peSPL, with 5 dB incremental steps. Part II investigated the characteristics of the 1 kHz TBOAE response in a large group of 705 neonatal ears, and provided clinical reference criteria based on these characteristics.

RESULTS

The study provided a series of reference parameters for 1 kHz TBOAE measurement in neonates. Based on the results, a suggested stimulus level and reference criteria for 1 kHz TBOAE measures with neonates were established. In addition, time-frequency analysis of the data gave new insight into the energy distribution of the neonatal TBOAE response.

CONCLUSION

TBOAE measures may be a useful method for investigating cochlear function at specific frequency ranges in neonates. However, further studies of both TBOAE time-frequency analysis and measurements in newborns are needed.

Ear asymmetries in middle-ear, cochlear, and brainstem responses in human infants

In 2004, Sininger and Cone-Wesson examined asymmetries in the signal-to-noise ratio (SNR) of otoacoustic emissions (OAE) in infants, reporting that distortion-product (DP)OAE SNR was larger in the left ear, whereas transient-evoked (TE)OAE SNR was larger in the right. They proposed that cochlear and brainstem asymmetries facilitate development of brain-hemispheric specialization for sound processing. Similarly, in 2006 Sininger and Cone-Wesson described ear asymmetries mainly favoring the right ear in infant auditory brainstem responses (ABRs). The present study analyzed 2640 infant responses to further explore these effects. Ear differences in OAE SNR, signal, and noise were evaluated separately and across frequencies (1.5, 2, 3, and 4 kHz), and ABR asymmetries were compared with cochlear asymmetries. Analyses of ear-canal reflectance and admittance showed that asymmetries in middle-ear functioning did not explain cochlear and brainstem asymmetries. Current results are consistent with earlier studies showing right-ear dominance for TEOAE and ABR. Noise levels were higher in the right ear for OAEs and ABRs, causing ear asymmetries in SNR to differ from those in signal level. No left-ear dominance for DPOAE signal was observed. These results do not support a theory that ear asymmetries in cochlear processing mimic hemispheric brain specialization for auditory processing.

Neonatal hearing screening: a combined click evoked and tone burst otoacoustic emission approach

OBJECTIVE

This study evaluated an alternative transient evoked otoacoustic emissions method for screening hearing in newborn babies that may reduce the referral rate of initial screening.

METHODS

A total of 1,033 neonates (2,066 ears) from two hospitals were recruited. Subjects had their hearing screened in both ears using a combined approach-both click evoked OAEs (CEOAEs) and 1kHz tone burst evoked OAEs (TBOAEs).

RESULTS

1kHz TBOAEs were more robust than CEOAEs in terms of emission response level and signal-to-noise ratio (SNR) at both 1 and 1.5kHz frequency bands. The prevalence rate for CEOAE and TBOAE responses in these two frequency bands was significantly different. The combined protocol significantly reduced the referral rate-by almost 2 percentage points for first time screening.

CONCLUSIONS

The implementation of a combined 1kHz TBOAE/CEOAE screening protocol is a feasible and effective way to reduce referral rates, and hence false positive rates, in neonatal hearing screening programs.

Effects of Maturation on Parameters Used for Pass/Fail Criteria in Neonatal Hearing Screening Programmes Using Evoked Otoacoustic Emissions

We aimed to investigate the incidence of false alarms that occurred with the pass/fail criteria used in a published series of neonatal hearing screening programmes, as a function of age. We analysed the database of 19137 normally hearing babies (38274 ears) tested in the Wessex Universal Neonatal Hearing Screening Project. Otoacoustic emissions were recorded prior to discharge from maternity units, using IL088 equipment. We assessed the pass/fail rate using the Wessex criteria and 10 other pass/fail criteria published in the literature. Using Pearson's correlation coefficient, a statistically significant correlation between signal-to-noise ratio at each of the frequency bands 1, 2, 3, 4 and 5 kHz and babies' age in hours at the 0.01 level was identified. The correlation was also significant (0.01 level) between age and frequency reproducibility in each of the bands at 1, 2, 3, 4 and 5 kHz as well as the whole reproducibility. The number of false alarms reduced significantly after the first 24 h of life with all the criteria examined. We conclude that in the first hours after birth due to insufficient maturation of the otoacoustic emission, there is a high rate of false alarms. This increase in the false alarm rate, whilst dependent on the criteria used, occurs with all criteria. This leads to the consideration of whether the establishment of age-dependent pass/fail criteria could reduce the false alarm rate and the subsequent strain on diagnostic centres.

[Characteristics of transient evoked otoacoustic emissions in newborn hearing screening program]

BACKGROUND

Otoacoustic emissions (OAE) are considered the main instrument of the Newborn Hearing Screening Program (NHSP).

AIM

To analyze the OAE of newborns evaluated in the NHSP.

METHOD

Transient evoked OAE recordings were captured in 1000 infants. The data were analyzed using the analysis of multivaried variance (Manova).

RESULTS

Reference tables were calculated for the over all OAE levels and for frequency bands, according to gender and ear. The duration of the exam in the nursery was shorter than in the clinic.

CONCLUSION

The level of the OAE was influenced by gender and ear, except for 0,7kHz. However, there were no observed differences between neonates without and with auditory risk.

Neonatal hearing screening: evaluation of tone-burst and click-evoked otoacoustic emission test criteria

OBJECTIVE

Click-evoked otoacoustic emissions (CEOAEs) are widely used in universal neonatal hearing screening programs. A common finding in many such programs is a relatively high false-positive rate. This is often due to infant physiological noise adversely affecting the emission recording, leading to a "refer" screening outcome. In an attempt to reduce false-positive screening outcomes related to the effects of noise on otoacoustic emission response detection, tone-burst-evoked otoacoustic emissions (TBOAEs) were included in a neonatal hearing screening program because TBOAEs may elicit a greater signal-to-noise ratio than CEOAEs. The research project compared the pass/refer rate for a CEOAE-based test using established pass/refer criteria with the pass/refer rate for screening criteria that were based on TBOAE results alone or on combined CEOAE and TEOAE results.

DESIGN

Neonates were recruited at the Hong Kong Adventist Hospital, and both CEOAEs and TBOAEs were performed. Six passing criteria were used in this study, based on CEOAEs only; CEOAEs plus 1 kHz TBOAEs; CEOAEs plus 2 kHz TBOAEs; CEOAEs plus 3 kHz TBOAEs; CEOAEs plus 1, 2, and 3 kHz TBOAEs; and TBOAEs only.

RESULTS

Data from 298 neonates (546 ears) were obtained. Criteria set 1, using CEOAEs only, demonstrated a pass rate of 79.1%, and 114 ears were referred. Criteria set 2, using CEOAEs together with TBOAEs recorded at 1 kHz, passed 39 more ears than Protocol 1, and the pass rate was 86.3%. Hence, the overall referral rate for total number of screened ears decreased by 7.2 percentage points. Criteria set 3, using CEOAEs together with TBOAEs recorded at 2 kHz, and Criteria set 4, using CEOAEs in conjunction with TBOAEs recorded at 3 kHz, gave pass rates similar to Criteria set 1. Criteria set 5, using TBOAE information at frequencies where CEOAEs were not rated as "pass," raised the pass rate from 79.1 to 87.6%, reducing the overall referral rate by 8.5 percentage points. Criteria set 6, in which neonates were screened with TBOAEs recorded at 1, 2, and 3 kHz, gave a pass rate of 78.4%, similar to results for the CEOAE-only procedure.

CONCLUSIONS

Both Criteria sets 2 and 5, which combined CEOAE and TBOAE recordings, gave significantly higher pass rates than Criteria sets 1, 3, 4, and 6. The results suggest that the introduction of combined CEOAE and TBOAE protocols may assist in the reduction of refer outcomes, and hence the false-positive rates, of neonatal hearing screening programs.

Neonatal screening for hearing impairment--The Oman experience

BACKGROUND

Oman introduced universal hearing screening at a national level in 2002 after piloting it in limited regions. Authors present their experiences.

METHODS

The screening had three phases. In Phase I, trained health staff of the delivery suits screened newborns by transient evoked otoacoustic emissions (TEOAE) test. In Phase II, otologists examined ears and repeated hearing tests after 6 weeks. Those who failed the repeat test were referred to a tertiary unit for the Phase III. Audiometrists tested their hearing by an Automated Auditory Brainstem Response (AABR). The rates of hearing disabled, false positive, yield and cost of screening were estimated.

RESULTS

The coverage of Phase I was 66.6% (21,387/32,125) and it had significant regional variation. Two thousand two hundred and eighty-seven (10.7%) newborns were suspected with hearing impairment. We detected 262 (1.2%) children with hearing impairment. In Phase II, 55 (0.26%) neonates failed the test. In Phase III, 36 neonates were tested with ABR. Eleven were lost to follow up and eight children were advised to undergo further investigations. Ten children were found normal and 26 had hearing impairment. Six neonates had sensory-neuronal hearing loss, 17 children had otitis media with effusion and three children had atresia of the middle ear. The yield of hearing screening was 1.2/1000. The cost of screening was US$7.1/newborn.

CONCLUSION

Universal hearing screening in Oman was useful but had teething problems. Proper planning, advocacy to the health staff and parents, commitment of the staff and care of the equipment are important. Such screening should be complimented with a defaulter retrieval and rehabilitation facilities for the hearing disabled.

The effect of the number of averaged responses on the measurement of transiently evoked otoacoustic emissions in newborns

OBJECTIVE

The aim of this study was to examine the effect of the number of averaged responses on the measurement of transiently evoked otoacoustic emissions (TEOAEs).

METHODS

The study was performed on the background of a universal newborn hearing screening program implemented in Iaso Maternity Hospital. Two groups of full-term newborns with normal otoacoustic emissions were studied. The first group included 58 newborns (115) ears, in which 260 low-noise samples, provided by the default setting of the equipment used (ILO88), were presented. The second group included 58 newborns (113) ears, in which 20-50 averaged responses were presented, until the "pass" criteria would be met. Statistical comparison between the following parameters recorded during TEOAE measurement was performed: Overall response, signal-to-noise ratios, reproducibility (whole and partial), stimulus intensity, stimulus stability, input noise, noise rejection level and duration of testing.

RESULTS

Statistically significant differences were found in most of these parameters, except for overall response, stimulus intensity and noise rejection level.

CONCLUSIONS

Although a smaller number of clicks is usually sufficient to obtain a "pass" in newborn hearing screening programs, the quality of recording of TEOAEs is significantly improved by increasing the number of averaged low-noise responses.

Making universal newborn hearing screening a success

OBJECTIVE

Following a long period of pilot study, Iaso maternity hospital established a universal newborn hearing screening program based on transiently evoked otoacoustic emissions (TEOAEs). The aim of this study is to present the improvement of outcome measures of this program, comparing the results of two groups of newborns screened successively.

METHODS

We analyzed data from two groups of full-term newborns screened at our setting. The first group included all newborns born and screened during the initial 3 years of application of the program and the second group included all newborns born and screened during the next 2 years. TEOAEs were performed during the first days after birth. All newborns who failed the initial test underwent repeat testing with TEOAEs before hospital discharge. Newborns with absence of otoacoustic emissions were referred to follow-up test after 1 month. Results were compared between the two groups.

RESULTS

The first group included 22,195 newborns-examined during 3 years and the second group included 25,032 newborns-examined during 2 years, due to reduction of the rate of newborns who missed screening. Refer rate was 3.1% for the first group and 2.1% for the second group. "Missed to follow-up" rate was reduced from 72.2% in the first group to 58.2% in the second group.

CONCLUSIONS

The rate of newborns who did not undergo screening and the rate of "missed to follow-up" newborns were reduced in time, due to various modifications of the protocol. Universal newborn hearing screening may be, thus, a feasible and cost effective method of identifying congenital hearing loss.

Asymmetric Cochlear Processing Mimics Hemispheric Specialization

Otoacoustic emissions or OAEs (reflections of cochlear energy produced during the processing of sound) were measured in response to two types of stimuli, rapid clicks and sustained tones, in each ear of neonates. OAEs were larger to tones when elicited in the left ear and to clicks when elicited in the right. This finding is similar to those of enhanced processing of tones in right auditory cortical areas and of rapid stimuli on the left, given strong crossed connections from ear to brain. These findings indicate that processing at the level of the ear may facilitate lateralization of auditory function in the brain.

Decreasing test time in newborn hearing screening

This study examined the effect of reducing the number of accepted responses in transiently evoked otoacoustic emissions based on the results of a universal neonatal hearing screening program. Our intention was to decrease the test time of newborns. A total of 464 ears were examined by using a universal newborn hearing-screening program implemented in a private maternity hospital. ILO88 Otodynamics Analyzer Quickscreen program was used for all testing and a two-stage procedure was adopted. In the first stage, the results were continuously evaluated for the 'pass' criteria, during the test, after at least 20 low-noise sweeps had been presented. As soon as the criteria were met, the test was interrupted and the results were recorded. In the second stage of the procedure, the test was continued and finally terminated after 260 quiet samples had been recorded. The results of each stage of this procedure were compared and evaluated. A total of 402 ears had normal otoacoustic emissions and only 62 ears had absent emissions. It was concluded that after a minimum of 20 averaged quiet responses, which we consider necessary in order to record reliable emissions and as soon as the 'pass' criteria were fulfilled the test could be terminated without affecting the 'pass-fail' rates which were similar in both stages. However, we believe that for diagnostic and clinical purposes, all 260 quiet samples must be used, because the results after the second stage indicated statistically better scores in response and reproducibility measures.

Community-based newborn hearing screening program in Taiwan

OBJECTIVE

Congenital bilateral hearing impairment occurs in approximately 1 in every 1000 live births. Universal newborn hearing screening (UNHS) programs are the most effective method for early diagnosis. Previously, newborn hearing screenings in Taiwan were often hospital-based. Our study is a community-based program designed to test the feasibility of performing neonatal hearing screening with a pay-for-test model, and to evaluate its acceptability to parents.

METHODS

From March 2000 to December 2002, two hospitals and four obstetric clinics in Tainan city participated in this study. The subjects were healthy newborns whose parents agreed to pay for otoacoustic emissions (OAE) hearing screening. They were tested in the newborn nursery before discharge. The protocol used an initial transient evoked otoacoustic emissions screening followed by a diagnostic auditory brainstem response (ABR) test.

RESULTS

A total of 10,008 healthy neonates were recruited, and 5938 newborns (59.3%) were tested. Prior to hospital discharge, 5403 of the newborns (91.0%) had passed the transient evoked otoacoustic emissions test. Referral for further testing was made in 9.0% of cases (535/5938). There were 140 babies lost to 1-month follow up. Only 395 infants (73.8%) of the infants that failed their first otoacoustic emissions tests underwent a second session at the outpatient clinic, and 91 babies failed. They were referred for further auditory brainstem response testing. Ultimately, nine babies were diagnosed with sensorineural hearing loss (SNHL).

CONCLUSIONS

There are difficulties in performing universal newborn hearing screening within Taiwan's health insurance system. This study was performed with the cooperation of hospitals and obstetric clinics, and was undertaken with a pay-for-screening model. Our program, with a pay-for-test model, of newborn hearing screening is feasible and was well regarded by parents in Tainan city. It could be run without the government's financial support.

The Effect of Different ‘Pass-Fail’ Criteria on the Results of a Newborn Hearing Screening Program

'Pass' criteria in newborn hearing screening programs are important, since they affect the operating characteristics of the programs. In the present study, we intended to compare the results of two screening procedures, using different 'pass' criteria, in two samples from the same pool of screened newborns. The subjects were divided into two study groups, screened consecutively during 6 months. Testing and all procedures were exactly the same in both groups, differing only in the 'pass' criteria. In the first group a signal-to-noise ratio of at least 3 dB in the frequency bands of 1-2, 2-3 and 3-4 kHz was considered necessary for a 'pass', whereas a signal-to-noise ratio > or =6 dB was used in the second group, at the same frequency bands. During the period of the study, no other minor or major modification of the protocol was applied. The comparison of the screening predischarge results between the two groups showed no statistically significant differences in the 'pass-refer' results. Thus, it appears that the 3-dB signal-to-noise ratio is as valid as the 6-dB criterion, and it may be confidently used, especially in settings where rescreening is not available.

Ear-canal acoustic admittance and reflectance measurements in human neonates. II. Predictions of middle-ear in dysfunction and sensorineural hearing loss

This report describes relationships between middle-ear measurements of acoustic admittance and energy reflectance (YR) and measurements of hearing status using visual reinforcement audiometry in a neonatal hearing-screening population. Analyses were performed on 2638 ears in which combined measurements were obtained [Norton et al., Ear Hear. 21, 348-356 (2000)]. The measurements included distortion-product otoacoustic emissions (DPOAE), transient evoked otoacoustic emissions (TEOAE), and auditory brainstem responses (ABR). Models to predict hearing status using DPOAEs, TEOAEs, or ABRs were each improved by the addition of the YR factors as interactions, in which factors were calculated using factor loadings from Keefe et al. [J. Acoust. Soc. Am. 113, 389-406 (2003)]. This result suggests that information on middle-ear status improves the ability to predict hearing status. The YR factors were used to construct a middle-ear dysfunction test on 1027 normal-hearing ears in which DPOAE and TEOAE responses were either both present or both absent, the latter condition being viewed as indicative of middle-ear dysfunction. The middle-ear dysfunction test classified these ears with a nonparametric area (A) under the relative operating characteristic curve of A = 0.86, and classified normal-hearing ears that failed two-stage hearing-screening tests with areas A = 0.84 for DPOAE/ABR, and A = 0.81 for TEOAE/ABR tests. The middle-ear dysfunction test adequately generalized to a new sample population (A = 0.82).

Ear-canal acoustic admittance and reflectance effects in human neonates. I. Predictions of otoacoustic emission and auditory brainstem responses

This report describes the extent to which ear-canal acoustic admittance and energy reflectance (YR) in human neonates (1) predict otoacoustic emission (OAE) levels and auditory brainstem response (ABR) latencies, and (2) classify OAE and ABR responses as present or absent. Analyses are reported on a subset of ears in which hearing screening measurements were obtained previously [Norton et al., Ear. Hear. 21, 348-356 (2000a)]. Tests on 1405 ears included YR, distortion-product OAEs, transient-evoked OAEs, and ABR. Principal components analysis reduced the 33 YR variables to 5-7 factors. OAE levels decreased and ABR latencies increased with increasing high-frequency energy reflectance. Up to 28% of the variance in OAE levels and 12% of the variance in ABR wave-V latencies were explained by these factors. Thus, the YR response indirectly encodes information on inter-ear variations in forward and reverse middle-ear transmission. The YR factors classify OAEs with an area under the relative operating characteristic (ROC) curve as high as 0.79, suggesting that middle-ear dysfunction is partly responsible for the inability to record OAEs in some ears. The YR factors classified ABR responses less well, with ROC areas of 0.64 for predicting wave-V latency and 0.56 for predicting Fsp.

Comparison of two methods of TEOAE recording in newborn hearing screening

This paper summarizes the results of trials performed in two hospitals, comparing the scoring of transient evoked otoacoustic emissions (TEOAEs) on the same neonates and within the same test session, recorded by the fully automatic device EchoScreen (Madsen Electronics/Fischer-Zoth GmbH) and ILO Otodynamics Ltd system. These trials form part of a larger project (Project Sentinel), whose primary aim is to stimulate the creation of new neonatal hearing screening programmes. Four thousand two hundred and forty-eight neonates were tested with both devices (8494 ears), in randomized order. The response scores obtained with the two devices are in full agreement in 98.72% of the tested ears. Considering the recording time, the fully automatic Echo Screen was, on average, about 3.6 times faster than the ILO88, bearing in mind, however, that when using ILO88, the end of the recording is decided by the operator on the basis of some mandatory decision rules.

Identification of neonatal hearing impairment: ear-canal measurements of acoustic admittance and reflectance in neonates

OBJECTIVES

1) To describe broad bandwidth measurements of acoustic admittance (Y) and energy reflectance (R) in the ear canals of neonates. 2) To describe a means for evaluating when a YR response is valid. 3) To describe the relations between these YR measurements and age, gender, left/right ear, and selected risk factors.

DESIGN

YR responses were obtained at four test sites in well babies without risk indicators, well babies with at least one risk indicator, and graduates of neonatal intensive care units. YR responses were measured using a chirp stimulus at moderate levels over a frequency range from 250 to 8000 Hz. The system was calibrated based on measurements in a set of cylindrical tubes. The probe assembly was inserted in the ear canal of the neonate, and customized software was used for data acquisition.

RESULTS

YR responses were measured in over 4000 ears, and half of the responses were used in exploratory data analyses. The particular YR variables chosen for analysis were energy reflectance, equivalent volume and acoustic conductance. Based on the view that unduly large negative equivalent volumes at low frequencies were physically impossible, it was concluded that approximately 13% of the YR responses showed evidence of improper probe seal in the ear canal. To test how these outliers influenced the overall pattern of YR responses, analyses were conducted both on the full data set (N = 2081) and the data set excluding outliers (N = 1825). The YR responses averaged over frequency varied with conceptional age (conception to date of test), gender, left/right ear, and selected risk factors; in all cases, significant effects were observed more frequently in the data set excluding outliers. After excluding outliers and controlling for conceptional age effects, the dichotomous risk factors accounting for the greatest variance in the YR responses were, in rank order, cleft lip and palate, aminoglycoside therapy, low birth weight, history of ventilation, and low APGAR scores. In separate analyses, YR responses varied in the first few days after birth. An analysis showed that the use of a YR test criterion to assess the quality of probe seal may help control the false-positive rate in evoked otoacoustic emission testing.

CONCLUSIONS

This is the first report of wideband YR responses in neonates. Data were acquired in a few seconds, but the responses are highly sensitive to whether the probe is fully sealed in the ear canal. A real-time acoustic test of probe fit is proposed to better address the probe seal problem. The YR responses provide information on middle-ear status that varies over the neonatal age range and that is sensitive to the presence or absence of risk factors, ear, and gender differences. Thus, a YR test may have potential for use in neonatal screening tests for hearing loss.

Identification of neonatal hearing impairment: distortion product otoacoustic emissions during the perinatal period

OBJECTIVES

1) To describe distortion product otoacoustic emission (DPOAE) levels, noise levels and signal to noise ratios (SNRs) for a wide range of frequencies and two stimulus levels in neonates and infants. 2) To describe the relations between these DPOAE measurements and age, test environment, baby state, and test time.

DESIGN

DPOAEs were measured in 2348 well babies without risk indicators, 353 well babies with at least one risk indicator, and 4478 graduates of neonatal intensive care units (NICUs). DPOAE and noise levels were measured at f2 frequencies of 1.0, 1.5, 2.0, 3.0, and 4.0 kHz, and for primary levels (L1/L2) of 65/50 dB SPL and 75/75 dB SPL. Measurement-based stopping rules were used such that a test did not terminate unless the response was at least 3 dB above the mean noise floor + 2 SDs (SNR) for at least four of five test frequencies. The test would terminate, however, if these criteria were not met after 360 sec. Baby state, test environment, and other test factors were captured at the time of each test.

RESULTS

DPOAE levels, noise levels and SNRs were similar for well babies without risk indicators, well babies with risk indicators, and NICU graduates. There was a tendency for larger responses at f2 frequencies of 1.5 and 2.0 Hz, compared with 3.0 and 4.0 kHz; however, the noise levels systematically decreased as frequency increased, resulting in the most favorable SNRs at 3.0 and 4.0 kHz. Response levels were least and noise levels highest for an f2 frequency of 1.0 kHz. In addition, test time to achieve automatic stopping criteria was greatest for 1.0 kHz. With the exception of "active/alert" and "crying" babies, baby state had little influence on DPOAE measurements. Additionally, test environment had little impact on these measurements, at least for the environments in which babies were tested in this study. However, the lowest SNRs were observed for infants who were tested in functioning isolettes. Finally, there were some subtle age affects on DPOAE levels, with the infants born most prematurely producing the smallest responses, regardless of age at the time of test.

CONCLUSIONS

DPOAE measurements in neonates and infants result in robust responses in the vast majority of ears for f2 frequencies of at least 2.0, 3.0 and 4.0 kHz. SNRs decrease as frequency decreases, making the measurements less reliable at 1.0 kHz. When considered along with test time, there may be little justification for including an f2 frequency at 1.0 kHz in newborn screening programs. It would appear that DPOAEs result in reliable measurements when tests are conducted in the environments in which babies typically are found. Finally, these data suggest that babies can be tested in those states of arousal that are most commonly encountered in the perinatal period.

Identification of neonatal hearing impairment: evaluation of transient evoked otoacoustic emission, distortion product otoacoustic emission, and auditory brain stem response test performance

OBJECTIVES

The purpose of this study was to compare the performance of transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), and auditory brain stem responses (ABRs) as tools for identification of neonatal hearing impairment.

DESIGN

A total of 4911 infants including 4478 graduates of neonatal intensive care units, 353 well babies with one or more risk factors for hearing loss (Joint Committee on Infant Hearing, 1994) and 80 well babies without risk factor who did not pass one or more neonatal test were targeted as the potential subject pool on which test performance would be assessed. During the neonatal period, they were evaluated using TEOAEs in response to an 80 dB pSPL click, DPOAE responses to two stimulus conditions (L1 = L2 = 75 dB SPL and L1 = 65 dB SPL L2 = 50 dB SPL), and ABR elicited by a 30 dB nHL click. In an effort to describe test performance, these "at-risk" infants were asked to return for behavioral audiologic assessments, using visual reinforcement audiometry (VRA) at 8 to 12 mo corrected age, regardless of neonatal test results. Sixty-four percent of these subjects returned and reliable VRA data were obtained on 95.6% of these returnees. This approach is in contrast to previous studies in which, by necessity, efforts were made to follow only those infants who "failed" the neonatal screening tests. The accuracy of the neonatal measures in predicting hearing status at 8 to 12 mo corrected age was determined. Only those infants who provided reliable, monaural VRA test results were included in the analysis. Separate analyses were performed without regard to intercurrent events (i.e., events between the neonatal and VRA tests that could cause their results to disagree), and then after accounting for the possible influence of intercurrent events such as otitis media and late-onset or progressive hearing loss.

RESULTS

Low refer rates were achieved for the stopping criteria used in the present study, especially when a protocol similar to the one recommended in the National Institutes of Health (1993) Consensus Conference Report was followed. These analyses, however, do not completely describe test performance because they did not compare neonatal screening test results with a gold standard test of hearing. Test performance, as measured by the area under a relative operating characteristic curve, were similar for all three neonatal tests when neonatal test results were compared with VRA data obtained at 8 to 12 mo corrected age. However, ABRs were more successful at determining auditory status at 1 kHz, compared with the otoacoustic emission (OAE) tests. Performance was more similar across all three tests when they were used to identify hearing loss at 2 and 4 kHz. No test performed perfectly. Using either the two- or three-frequency pure-tone average (PTA), with a fixed false alarm rate of 20%, hit rates for the neonatal tests, in general, exceeded 80% when hearing impairment was defined as behavioral thresholds > or =30 dB HL. All three tests performed similarly when a two-frequency (2 and 4 kHz) PTA was used as the gold standard; OAE test performance decreased when a three-frequency PTA (adding 1 kHz) was used as the gold standard definition. For both PTA and all three neonatal screening measures, however, hit rate increased as the magnitude of hearing loss increased.

CONCLUSIONS

Singly, all three neonatal hearing screening tests resulted in low refer rates, especially if referrals for follow-up were made only for the cases in which stopping criteria were not met in both ears. Following a protocol similar to that recommended in the National Institutes of Health (1993) Consensus Conference report resulted in refer rates that were less than 4%. TEOAEs at 80 dB pSPL, DPOAE at L1 = 65, L2 = 50 dB SPL and ABR at 30 dB nHL measured during the neonatal period, and as implemented in the current study, performed similarly at predicting behavioral hearing status at 8 to 12

Identification of neonatal hearing impairment: summary and recommendations

OBJECTIVES

This article summarizes the results of a multi-center study, "Identification of Neonatal Hearing Impairment," sponsored by the National Institutes of Health. The purpose of this study was to determine the performance characteristics of three measures of peripheral auditory system status, transient evoked otoacoustic emissions (TEOAEs), distortion product otoacoustic emissions (DPOAEs), and auditory brain stem responses (ABR), applied in the neonatal period in predicting hearing status at 8 to 12 mo corrected age.

DESIGN

The design and implementation of this study are described in the first two articles in this series. Seven institutions participated in this study; 7179 infants were evaluated. Graduates of the neonatal intensive care unit and well babies with one or more risk factors for hearing loss were targeted for follow-up testing using visual reinforcement audiometry (VRA) at 8 to 12 mo corrected age. Neonatal test performance was evaluated using the VRA data as the "gold standard."

RESULTS

The major results of the study are described in the nine articles preceding this summary article. TEOAEs in response to an 80 dB pSPL click, DPOAEs in response to L1 = 65 and L2 = 50 dB SPL and ABR in response to a 30 dB nHL click performed well as predictors of permanent hearing loss of 30 dB or greater at 8 to 12 mo corrected age. All measures were robust with respect to infant state, test environment and infant medical status. No test performed perfectly.

CONCLUSIONS

Based on the data from this study, the 1993 National Institutes of Health Consensus Conference-recommended protocol-an OAE test followed by an ABR test for those infants failing the OAE test-would result in low referral rate (96 to 98%). TEOAEs for 80 dB pSPL, ABR for 30 dB nHL and DPOAEs for L1 = 65 dB SPL and L2 = 50 dB SPL perform well in predicting hearing status based on the area under the relative operating characteristic curve. Accuracy for the OAE measurements are best when the speech awareness threshold or the pure-tone average for 2.0 kHz and 4 kHz are used as the gold standard. ABR accuracy varies little as a function of the frequencies included in the gold standard. In addition, 96% of those infants returning for VRA at 8 to 12 mo corrected age were able to provide reliable ear-specific behavioral thresholds using insert earphones and a rigorous psychophysical VRA protocol.

Identification of neonatal hearing impairment: a multicenter investigation

OBJECTIVES

This article describes the design of a multicenter study sponsored by the National Institutes of Health. The purpose of this study was to determine the accuracy of three measures of peripheral auditory system status (transient evoked otoacoustic emissions, distortion product otoacoustic emissions, and auditory brain stem responses) applied in the perinatal period for predicting behavioral hearing status at 8 to 12 mo corrected age. The influences of the infant's medical status, the test environment, and test and response parameters on test performance were examined.

DESIGN

Seven institutions participated in this study. There were 7179 infants evaluated in the perinatal period. All graduates of the neonatal intensive care unit (4478) and well babies with one or more risk factor for hearing loss (353) were targeted for follow-up testing using visual reinforcement audiometry (VRA) at 8 to 12 mo corrected age. Well babies without any risk indicators (N = 2348) were not targeted for follow-up VRA testing. However, 80 of these well babies did not pass the screening protocol and thus were targeted for follow-up VRA testing as well. Perinatal test performance was evaluated using the VRA data as the "gold standard."

RESULTS

The results of this study are described in a series of 11 articles following this introductory article.

CONCLUSIONS

The evaluation of newborn hearing tests required a longitudinal study in which newborn test results were compared with a gold standard based on behavioral audiometric assessment. Such an evaluation was possible because all newborns, passes as well as refers, were followed up long enough to permit reliable behavioral measurements. In addition, prenatal, perinatal, and maternal history information, test environment, and test parameter information were collected to provide data that led to a complete description of factors affecting test outcomes. All of these data were obtained in a sample of sufficient ethnic, medical, and geographic diversity in efforts to increase the generalizability of the results. Finally, the data were combined in a relational data base to examine the factors that influence test performance. Specific information related to these issues is presented in the articles that follow.

Identification of neonatal hearing impairment: experimental protocol and database management

OBJECTIVE

The purposes of this article are to describe the overall protocol for the Identification of Neonatal Hearing Impairment (INHI) project and to describe the management of the data collected as part of this project. A well-defined protocol and database management techniques were needed to ensure that data were 1) collected accurately and in the same way across sites; 2) maintained in a database that could be used to provide feedback to individual sites regarding enrollment and the extent to which the protocol was complete on individual subjects; and 3) available to answer project questions. This article describes techniques that were used to meet these needs.

DESIGN

This study was a prospective, randomized study that was designed to evaluate auditory brain stem responses, transient evoked otoacoustic emissions, and distortion product otoacoustic emissions as hearing-screening tools, and to relate neonatal test findings to hearing status, defined by visual reinforcement audiometry at 8 to 12 mo of age. Measures of middle-ear function also were obtained at some sites as part of the neonatal test battery. In addition, other clinical and demographic data were gathered to determine the extent to which factors, other than auditory status, influenced test behavior. Three groups were evaluated: neonatal intensive care unit (NICU) infants (those who spent 3 or more days in a NICU), well babies with risk factors for hearing loss, and well babies without risk factors. Six centers participated in the trial. The testers for the project included audiologists, technicians, audiology graduate students, and medical research staff. The same computerized neonatal test program was applied at each center. This program generated the neonatal test database automatically. Clinical and demographic data were collected by means of concise data collection forms and were entered into a database at each site. After the neonatal test, subjects from the NICU and at-risk well babies were evaluated with visual reinforcement audiometry starting at 8 to 12 mo of age. All data were electronically transmitted to the core site where they were merged into one overall database. This database was exercised to provide feedback and to identify discrepancies throughout the course of the study. In its final form, it served as the database on which all analyses were performed.

RESULTS AND CONCLUSION

The protocol was a departure from typical hearing screening procedures in terms of 1) its regimented application of three screening measures; 2) the detailed information that was obtained regarding subject clinical and demographic factors; and 3) its application of the same procedures across six centers having diverse geographic location and subject demographics. A learning curve for successfully executing the study protocols was observed. Throughout the study, monthly reports were generated to monitor subject enrollment, check for data completeness, and to perform data integrity checks. In combination with monthly data reports and checks that occurred throughout the progression of the study, miscellaneous data audits were performed to check accuracy of neonatal testing programs and to cross-check information entered in the clinical and demographic database. The data management techniques used in this project helped to ensure the quality of the data collection process and also allowed for detailed analyses once data were collected. This was particularly important because it enabled us to evaluate not only the performance of individual measures as screening tools, but also permitted an evaluation of the influence of other variables on screening test results.