Otoacoustic emission criteria for neonatal hearing screening

International consensus (ICON) on audiological assessment of hearing loss in children

The prevalence of hearing loss in newborns and infants is estimated between 1 to 3.47 cases per 1000 live births. Early diagnosis and rehabilitation of congenital hearing loss are mandatory in order to achieve a satisfactory linguistic and cognitive development. Without appropriate opportunities to learn language, these children will fall behind their normal hearing peers in communication, cognition, reading and socio-emotional development. After promising results, neonatal screening for hearing loss and audiological evaluation are becoming more extensively carried out. In planning universal neonatal hearing screening programs, transient evoked otoacoustic emissions and auditory brainstem responses are the gold standard for the screening and diagnosis program. However, there is no consensus regarding the use of audiometry and other electrophysiological tests (such as auditory steady-state responses) in current practices. Several screening and audiological assessment procedures have been described and advocated all around the world. But, a systematic scheme of performing diagnosis in the pediatric audiology population is lacking. A consensus conference was held at the International Federation of Oto-rhino-laryngological Societies Congress, in June 2017, to discuss the different current practices and to identify the best neonatal hearing screening and audiological assessment management. This article is intended to provide professionals with recommendations about the "best practice" based on consensus opinion of the session's speakers, and a review of the literature on the efficacy of various assessment options for children with hearing loss.

Criteria for detection of transiently evoked otoacoustic emissions in schoolchildren

OBJECTIVES

The aim was to compare, on the same dataset, existing detection criteria for transiently evoked otoacoustic emissions (TEOAEs) and to select those most suitable for use with school-aged children.

METHODS

TEOAEs were recorded from the ears of 187 schoolchildren (age 8-10 years) using the Otodynamics ILO 292 system with a standard click stimulus of 80dB peSPL. Pure tone audiometry and tympanometry were also conducted. Global and half-octave-band (at 1, 1.4, 2, 2.8, 4kHz) values of OAE signal-to-noise ratio (SNR), reproducibility, and response level were determined. These parameters were used as criteria for detection of TEOAEs. In total, 21 criteria based on the literature and 3 new ones suggested by the authors were investigated.

RESULTS

Pure tone audiometry and tympanometry screening generated an ear-based failure rate of 7.49%. For TEOAEs, there was a huge variability in failure rate depending on the criteria used. However, three criteria sets produced simultaneous values of sensitivity and specificity above 75%. The first of these criteria was based only on a global reproducibility threshold value above 50%; the second on certain global reproducibility and global response values; and the third involved exceeding a threshold of 50% band reproducibility. The two criteria sets with the best sensitivity were based on global reproducibility, response level, and signal-to-noise ratio (with different thresholds across frequency bands).

CONCLUSIONS

TEAOEs can be efficiently used to test the hearing of schoolchildren provided appropriate protocols and criteria sets are used. They are quick, repeatable, and simple to perform, even for nonaudiologically trained personnel. Criteria with high sensitivity (89%) were identified, but they had relatively high referral rates. This is not so much a problem in schoolchildren as it is in newborns because with schoolchildren pure tone audiometry and tympanometry can be performed immediately or at a follow-up session. Nevertheless, high referral rates lead to increased screening cost; for that reason, three less rigorous criteria with high values of both sensitivity and specificity (75% and above) are recommended.

Chirp-evoked otoacoustic emissions in children

OBJECTIVE

The purpose of the study was to investigate the properties of otoacoustic emissions (OAEs) evoked by chirp stimuli and compare them with standard click-evoked OAEs. Differences between evoked OAEs in children with and without spontaneous otoacoustic emissions (SOAEs) were also assessed.

METHODS

OAEs were first recorded from 54 children (age 4-10 years) in a screening setup. In each ear five OAE measurements were made using two types of chirps (7.5 ms and 10.5 ms) at around 70 dB pSPL; clicks at 70 and 80 dB pSPL; and a standard synchronized SOAE stimulation protocol. Tympanometry was also conducted. Pass/refer criteria based on signal to noise ratios (SNRs) were applied to all OAEs. Pass/refer rates from all methods (OAEs evoked by chirps and clicks, and tympanometry) were compared. Additionally, half-octave-band values of OAE SNRs and response levels were used to assess statistical differences.

RESULTS

Chirp-evoked OAEs generated a similar number of passes to click-evoked OAEs when the same level of stimulus was used. When using lower stimulus levels, both chirp- and click-evoked OAEs diagnosed nearly all ears that failed tympanometry. The response levels and SNRs of OAEs evoked by clicks and chirps were very similar. The highest response levels were in the 1.4 kHz half-octave band. The SNRs for ears with SOAEs were highest at 1.4 kHz, whereas they were at 4 kHz for ears without SOAEs. Both response levels and SNRs were higher by about 5 dB for ears with SOAEs than ears without SOAEs. Also all ears with SOAEs generated a pass result in screening, while ears without SOAEs gave a pass less frequently (at least 30% fewer cases).

CONCLUSIONS

The results suggest that performance of chirp-evoked OAEs for screening purposes is similar to click-evoked OAEs when the same stimulus level is applied. OAEs evoked with lower stimulus levels (70 vs. 80 dB pSPL) are more sensitive to middle ear pathology. The presence of SOAEs significantly influences the pass rates of OAEs evoked by chirps and clicks.

Frequency distribution of synchronized spontaneous otoacoustic emissions showing sex-dependent differences and asymmetry between ears in 2- to 4-day-old neonates

OBJECTIVE

The mature pattern of frequency distribution of synchronized spontaneous otoacoustic emissions (SSOAEs) has been reported to be bimodal in adults and children between 5 and 11 years of age; however, little is known about the distribution in neonates between 2 and 4 days after birth. Furthermore, overall differences in frequency distribution resulting from difference in sex and asymmetry between ears have not been carefully examined. The aim of this study is to determine the frequency distribution of SSOAEs in neonates at 2 to 4 days of age, evaluate the maturity of the pattern of distribution in this age group, and to evaluate the effects of differences in sex and asymmetry between left and right ears on the frequency distribution.

METHODS

We evaluated 224 ears in 112 newborns (59 girls, 53 boys) whose ages ranged from 2 to 4 days. The SSOAEs were measured using ILO96.

RESULTS

Most of the SSOAEs (86.5%) appeared at frequencies between 1.01 and 4.50 kHz. The overall frequency distribution of the SSOAEs showed a 'peak-valley-peak' pattern when plotted. Two peaks with maxima at 1.41-1.60 and 3.01-3.20 kHz were separated by a valley with a minimum at 2.41-2.60 kHz. Both girls and boys had approximate monomodal patterns in the distribution of SSOAEs. Significant sex-dependent differences were noted with more SSOAEs at the lower frequencies (<or=2 kHz) in boys (46.1%) than in girls (32.0%) (P<0.05) and more SSOAEs at the higher frequencies (2.51- 4.50 kHz) in girls (50.9%) than in boys (37.5%) (P<0.05). Both the right and left ears showed the 'peak-valley-peak' pattern that was similar to the overall distribution pattern. But, compared with the peaks measured in the left ears at 1.01-1.50 and 3.01-3.50 kHz, the peaks of the right ears at 1.51-2.00 and 2.51-3.00 kHz were much closer to the valley.

CONCLUSIONS

The overall distribution of frequency of SSOAEs in 2- to 4-day-old neonates had the similar mature 'peak-valley-peak' distribution pattern seen in adults. Significant sex-dependent differences of the SSOAEs frequency distributions have been found. However, only slight ear asymmetries of the SSOAEs frequency distributions can observed in this age group.

The results of newborn hearing screening by means of transient evoked otoacoustic emissions

OBJECTIVE

The incidence of sensorineural hearing loss is between 1 and 3 per 1000 in healthy neonates and 2-4 per 100 in high-risk children. Transient evoked otoacoustic emissions (TEOAEs) represent a method which can be applied to all newborns prior to hospital discharge, enabling early identification of hearing loss. The aim of the study was to evaluate the results of newborn hearing screening by means of TEOAEs.

METHODS

Between 01.10.2002 and 30.09.2003, 5601 newborns born in the University Hospital in Poznan, Poland were screened with ERO SCAN (MAICO). Healthy neonates were screened in the second or third day of life and children treated in pathology unit--when their general condition was stable. The risk factors of hearing loss were recorded in a questionnaire. Children who failed the screening test or had risk factors of hearing impairment were referred to the outpatient clinic for further evaluation.

RESULTS

Risk factors were identified in 739 newborns. The most often risk factors were: use of ototoxic drugs, low Apgar score and prematurity. Positive test result was obtained in 219 (3.91%) children unilaterally and in 137 (2.45%) bilaterally. In healthy children the prevalence of positive results was 3.56% and in high-risk infants 24.9%. The relative risk of positive test results was the highest in infants with positive family history (RR=7.5), congenital malformations (RR=6.7) and low Apgar score (RR=5). Of the group of 912 children, who were referred to the specialist, only 218 turned up to be assessed during the observation period and had the additional otoacoustic emission test performed. There was not any significant difference in the percentage of children with and without risk factors who turned up for the second test and in whom the result was positive (39.7% versus 40.3%). In 41.9% children with risk factors whose screening test was negative, the second exam gave positive result.

CONCLUSIONS

The incidence of positive results in newborn hearing screening is much higher than the prevalence of hearing loss in general population and these results need verification by more precise methods. However, TEOAEs enable to select children who should be referred for audiological evaluation.

Despistaje de la hipoacusia neonatal: resultados después de 3 años de iniciar nuestro programa

Since the 90s there increasing interest in early detection of neonatal hearing loss due to the feasibility of universal neonatal screening as well as to the possibility of early intervention. This has led to set up neonatal screening programs based upon otoacoustic emissions and to a great increase in the number of publications in the field. Our hospital started a neonatal hearing loss screening program using otoacoustic emission in March 2000. We used a Capella Cochlear Emissions (MADSEN electronics) equipment. Until May 2003 we have performed the test in 6372 children with a median age of 71 days. In our study, the sensibility of the test was 90.9% and the specificity 99.7%. Our results are similar to those reported in the literature although the age of the children was higher and we have found an incidence of hearing loss lower than other studies.

Distortion evoked otoacoustic emission using GSI 70 analyzer for neonatal screening

OBJECTIVE

Following the recommendation of the United State National Institute of Health Consensus Conference in 1993, otoacoustic emissions (OAE) are now used internationally for hearing screening. The GSI 70 OAE screener provides the means for carrying out OAE recordings within a short period of time and includes an automatic evaluation of results. The aim of this study was to determine the reliability of recordings in comparison with available standards in brainstem audiometry.

METHOD

OAE recorded in 29 hearing-impaired suspected infants and young children (aged 1 months-7 years old) in order to compare the result of the GSI 70 screener with the result of ABR. This study was conducted in the outpatient clinic of the Tokyo University Hospital.

RESULT

Our study showed that the GSI 70 screener has higher false negative rate compared with ABR results (P<0.01). Consequently, an OAE measuring method, is also provides high sensitivity and easy to use. However, there was no trend toward increased refer rates with increased age.

CONCLUSION

Our findings show that the GSI 70 screener can meet the demands of systematic hearing screening in infants and young children, although there is a tendency to miss cochlear impaired cases.

The effect of high-pass filtering on TEOAE in 2-month-old infants

The aim of the present study was to investigate the effect of high-pass filtering on TEOAE obtained from 2-month-old infants as a function of filter cut-off frequency, activity states and pass/fail status of infants. Two experiments were performed. In Experiment 1, 100 2-month-old infants (200 ears) in five activity states (asleep, awake but peaceful, sucking a pacifier, feeding, restless) were tested by use of TEOAE technology. Five different filter conditions were applied to the TEOAE responses post hoc. The filter conditions were set at 781 Hz (default setting), 1.0, 1.2, 1.4 and 1.6 kHz. Results from this experiment showed that TEOAE parameters such as whole-wave reproducibility (WR) and signal-to-noise ratio (SNR) at 0.8 kHz and 1.6 kHz, changed as a function of the cut-off frequency. The findings suggest that the 1.6 kHz and 1.2 kHz filter conditions are optimal for WR and SNR pass/fail criteria, respectively. Although all infant recordings appeared to benefit from the filtering, infants in the noisy states seemed to benefit the most. In Experiment 2, the high-pass filtering technique was applied to 23 infants (35 ears) who apparently failed the TEOAE tests on initial screening but were subsequently awarded a pass status based on the results from a follow-up auditory brainstem response (ABR) assessment. The findings showed a significant decrease in noise contamination of the TEOAE with a corresponding significant increase in WR. With high-pass filtering at 1.6 kHz, 21/35 ears could be reclassified into the pass category.

Data processing options and response scoring for OAE-based newborn hearing screening

Scoring of click-evoked otoacoustic emissions (CEOAEs) is typically achieved by the evaluation of the reproducibility of the whole emission and/or within narrow bands. Screening outcomes are influenced not only by the specific combination of the subdivision scheme (i.e., the number, position, and bandwidth of the narrow bands) and the threshold used to determine pass and refer, but also by the accuracy with which the reproducibility is estimated. This study was designed to examine what factors affect the accuracy of the reproducibility estimate and how the accuracy of the reproducibility estimate together with the choice of the subdivision scheme/thresholds affect CEOAE scoring. Simulations with real CEOAEs corrupted with synthesized noise indicated that the reproducibility estimate is influenced by time-windowing and band-pass filtering: the longer the time-window or the broader the bandwidth of the filter, the more accurate the estimate. Quantitative figures on numerical scoring were given in terms of the referral rate and were derived from CEOAEs recorded in a clinical environment from more than 3400 newborns. The narrow bands were extracted according to 12 different subdivision schemes covering the 1.5-4-kHz range. The referral rate was found to depend on the subdivision scheme being used: (i) the worst results were obtained considering four narrow bands at 1.6-2.4-3.2-4 kHz; (ii) the best results were obtained considering two narrow bands at 2.25 and 3.75 kHz; (iii) bandwidths greater than 1 kHz resulted in the lowest referral rates. Also, scoring based on the extraction of four narrow bands produced the most unstable results, i.e., a small change in the threshold might cause even a great change in the referral rate.