Assessment of Hearing Impairment in Sick Newborns: A Prospective Observational Study

BACKGROUND

 Undiagnosed neonatal hearing loss causes severe language, cognitive, and behavioral problems in children. Sick newborns who spend 48 hours in the neonatal intensive care unit (NICU) have a 10- to 20-fold increased risk of permanent hearing loss. The aim of this study is to identify hearing impairment in high-risk sick newborns who spend at least 48 hours in the NICU.

METHODS

 The present prospective observational study was conducted at a single center. All sick neonates admitted to the NICU for a minimum of 48 hours at the JK Lon Hospital, Zanana Hospital, and Mahila Chikitsalaya, Sawai Man Singh (SMS) Medical College, Jaipur, Rajasthan, India, from June 2017 to May 2018 were considered eligible for the study. The primary outcome was the assessment of hearing loss of high-risk newborns using otoacoustic emissions at the time of discharge, six weeks of age, and automated auditory brainstem response (AABR) at three months of chronological age. The secondary outcome was to analyze the association of hearing loss with different risk factors in high-risk neonates.

RESULTS

 A total of 150 infants who had one or more risk factors were studied, 60 were female and 90 were male. No statistically significant difference in hearing loss was observed based on birth weight, sex, and gestational age. The first distortion-product otoacoustic emission (DPOAE) screening was done on infants at the time of discharge from the NICU. Eighty-three infants (55.33%) had "refer" on the first DPOAE and the remaining 67 (44.67%) were passed results at the time of discharge. At six weeks of life, on repeat screening with a second DPOAE test, 36% "refer" on the first screen had a "refer" result on the second DPOAE. However, 4.4% "pass" on the first screen turned out to be "refer" on the second screen. These 33 infants who had "refer" results on the second screen were subjected to testing. At 10 weeks of life, AABR was performed on 33 infants. Eleven infants out of 33 had sensorineural hearing loss (SNHL) on AABR. Hearing impairment with the DPOAE test was observed with risk factors neonatal hyperbilirubinemia (NHH), hypoxic ischemic encephalopathy (HIE), and very low birth weight (VLBW) and was statistically significant among all risk factors. But, no such association (between hearing impairment and risk factors) was observed with the AABR test. In our study, we found that the duration of mechanical ventilation in mean days 7.67±6.24 had statistically significant SNHL compared to the lesser duration of mechanical ventilation (p<0.001).

CONCLUSION

Two-stage DPOAE done prior to AABR is helpful in the early detection of hearing loss.

[Analysis of first-time hearing screening tests among singlets and twin neonates in neonatal intensive care unit]

Objective:To investigate the failure in the hearing screening test among twin neonates in neonatal intensive care unit （NICU） and to further clarify the etiology of neonatal hearing impairment, thus to provide insights into prevention and early intervention. Methods:Automated auditory brainstem response（AABR）, distortion product otoacoustic emission（DPOAE） and acoustic immittance were performed on 1452 neonates（including 130 twins） admitted in NICU from January 2015 to June 2018 and the risk factors including premature birth, hyperbilirubinemia, neonatal respiratory distress syndrome, etc. were analyzed retrospectively by univariate chi-square test and multivariate logistic regression analysis. Results:The incidence of C-section, premature birth, hyperbilirubinemia, low birth weight, very low birth weight, in-vitro fertilization, pregnancy-induced hypertension syndrome and formula or mixed feeding among twin neonates were significantly higher than those of singleton neonates （P<0.05）. The pass rates of the first-time AABR, DPOAE and acoustic immittance were significantly lower than singleton neonates. The proportion of twin neonates who failed the initial screening but recovered in the following test was as high as 72.86%. AABR pass rate was correlated with congenital heart disease, neonatal respiratory distress syndrome, C-section and （very） low birth weight. The pass rate of DPOAE was correlated with low birth weight and C-section. The pass rate of acoustic immittance was correlated with preterm birth, C-section, low birth weight, gestational diabetes and gestational hypertension. The pass rate of diagnostic ABR was associated with gestational diabetes. And the pass rate of diagnostic DPOAE was associated with maternal age ≥40 years old. Conclusion:The first-time hearing screening pass rate of twin neonates in NICU is lower than that of neonatal singleton. Most twin neonates who fail in the first screening test will recover. Preterm birth, neonatal respiratory distress syndrome, （very） low birth weight, congenital heart disease, gestational diabetes, pregnancy-induced hypertension syndrome, maternal age ≥ 40 years old and C-section are associated with the first-time failure in hearing screening tests among twin neonates, thus entailing close follow-up.

Comparison of Two-Step Transient Evoked Otoacoustic Emissions and One-Step Automated Auditory Brainstem Response for Universal Newborn Hearing Screening Programs in Remote Areas of China

Objective: To compare the hearing screening results of two-step transient evoked otoacoustic emissions (TEOAE) and one-step automatic auditory brainstem response (AABR) in non-risk newborns, and to explore a more suitable hearing screening protocol for infants discharged within 48 h after birth in remote areas of China. Methods: To analyze the age effect on pass rate for hearing screening, 2005 newborns were divided into three groups according to screening time after birth: <24, 24-48, and 48-72 h. All subjects received TEOAE + AABR test as first hearing screen, and those who failed in any test were rescreened with TEOAE + AABR at 6 weeks after birth. The first screening results of AABR and TEOAE were compared among the three groups. The results of two-step TEOAE screening and one-step AABR screening were compared for newborns who were discharged within 48 h. The time spent on screening was recorded for TEOAE and AABR. Results: The pass rate of TEOAE and AABR increased significantly with the increase of first screening time (P < 0.05), and the false positive rate decreased significantly with the increase of first screening time (P < 0.05). The failure rate of first screening of AABR within 48 h was 7.31%, which was significantly lower than that of TEOAE (9.93%) (P < 0.05). The average time spent on AABR was 12.51 ± 6.36 min, which was significantly higher than that of TEOAE (4.05 ± 1.56 min, P < 0.05). The failure rate of TEOAE two-step screening was 1.59%, which was significantly lower than one-step AABR. Conclusions: Compared with TEOAE, AABR screening within 48 h after birth can reduce the failure rate and false positive rate of first screening. However, compared with TEOAE two-step screening, one-step AABR screening has higher referral rate for audiological diagnosis. In remote areas of China, especially in hospitals with high delivery rate, one-step AABR screening is not feasible, and two-step TEOAE screening protocol is still applicable to UNHS screening as more and more infants discharged within 48 h after birth.

[Duration of automated auditory brainstem response test for the initial hearing screening and influencing factors for the duration in neonates]

OBJECTIVE

To study the duration of automated auditory brainstem response (AABR) test for initial hearing screening and the factors influencing the duration in neonates.

METHODS

A total of 472 neonates who were admitted to the neonatal intensive care unit (NICU) were enrolled as the study group and 182 healthy neonates were enrolled as the healthy control group. The influence of the duration of AABR test on the initial screening results was observed in the two groups. The influencing factors for the AABR test duration were analyzed.

RESULTS

In the AABR screening of 180, 360, and 540 seconds, the study group had a failure rate of 41.5%, 28.4%, and 24.4% respectively, while the healthy control group had a failure rate of 31.3%, 19.8%, and 15.4% respectively, showing a decreasing trend with the extension of test time in both groups (P<0.05). In the two groups, the screening results of 180-second testing were moderately consistent with those of 360- or 540-second testing (Kappa<0.75, P<0.05), and the screening results of 360-second testing were highly consistent with those of 540-second testing (Kappa>0.75, P<0.05). In the study group, the median duration of AABR test was 108 seconds (95%CI: 97-120 seconds), which was significantly longer than the duration of 75 seconds (95%CI: 65-85 seconds) in the healthy control group (P<0.05). The Cox regression analysis showed that maternal age ≥35 years, anemia, and electrolyte disturbance (RR<1, P<0.05) were independent risk factors for prolonged AABR test duration, while the prolonged continuous positive airway pressure-assisted ventilation was a protective factor (RR>1, P<0.05).

CONCLUSIONS

The AABR test time of 360-540 seconds for initial hearing screening helps to reduce false positive results due to environmental and risk factors in neonates. It may be useful to reduce the false positive results of AABR screening before discharge by taking corresponding intervention measures for NICU neonates with high risk factors.

Neonatal hearing screening in remote areas of China: a comparison between rural and urban populations

Objectives Universal neonatal hearing screening (UNHS) started late in some underdeveloped areas in China, with relatively scarce screening resources and a wide regional distribution. This study aimed to compare the screening performance between rural and urban populations, and to examine the characteristics and problems of UNHS in underdeveloped regions in China. Methods A two-step hearing screening program was used in neonates born in Liuzhou Maternal and Child Health Hospital and in patients who were born in other hospitals, but admitted to the neonatal intensive care unit. This program involved distortion product otoacoustic emission and automated auditory brainstem response. Characteristics of each newborn, as well as the screening outcomes and performance were compared between rural and urban populations. Results A total of 19,098 newborns were screened with a referral rate of 17.9% at the first step. Sixty-three (0.33%) newborns had hearing loss. The prevalence of permanent hearing loss was 2.25‰. The average screening age was significantly older in the rural population than in the urban population in the first ( P < 0.01) and second steps of screening ( P < 0.05). The rural population had a higher referral rate in both steps than the urban population ( P < 0.01). The follow-up rate was much lower in the rural population than in the urban population ( P < 0.05), but dramatically increased in 2014 compared with the previous 2 years. Conclusions A low follow-up rate is a critical issue when carrying out UNHS in developing countries, such as China, especially for rural populations. The government should establish more hearing referral centres to increase service coverage and supply financial assistance for low-income populations.

Serum bilirubin and bilirubin/albumin ratio as predictors of bilirubin encephalopathy

BACKGROUND AND OBJECTIVE

Bilirubin/albumin ratio (B/A) may provide a better estimate of free bilirubin than total serum bilirubin (TSB), thus improving identification of newborns at risk for bilirubin encephalopathy. The objective of the study was to identify thresholds and compare specificities of TSB and B/A in detecting patients with acute and posttreatment auditory and neurologic impairment.

METHODS

A total of 193 term/near-term infants, admitted for severe jaundice to Cairo University Children's Hospital, were evaluated for neurologic status and auditory impairment (automated auditory brainstem response), both at admission and posttreatment by investigators blinded to laboratory results. The relationships of TSB and B/A to advancing stages of neurotoxicity were compared by using receiver operating characteristic curves.

RESULTS

TSB and B/A ranged from 17 to 61 mg/dL and 5.4 to 21.0 mg/g, respectively; 58 (30%) of 193 subjects developed acute bilirubin encephalopathy, leading to kernicterus in 35 infants (13 lethal). Auditory impairment was identified in 86 (49%) of 173 infants at admission and in 22 of 128 at follow-up. In the absence of clinical risk factors, no residual neurologic or hearing impairment occurred unless TSB exceeded 31 mg/dl. However, transient auditory impairment occurred at lower TSB and B/A (22.9 mg/dL and 5.7 mg/g, respectively). Intervention values of TSB and B/A set at high sensitivity to detect different stages of neurotoxicity had nearly the same specificity.

CONCLUSIONS

Both TSB and B/A are strong predictors of neurotoxicity, but B/A does not improve prediction over TSB alone. Threshold values detecting all affected patients (100% sensitivity) increase with advancing severity of neurotoxicity.

Influence of postconceptional age on universal newborn hearing screening in NICU-babies

The feasibility of universal newborn hearing screening (UNHS) using automated auditory brainstem response (AABR) devices in the neonatal intensive care unit (NICU) is already well demonstrated. The aim of this study was to find out whether the postconceptional age (PCA) of the babies at the time of the AABR measurement has an influence on the measuring results and to determine the earliest time point for a reliable hearing screening in preterm neonates. Hearing screening measurements of 634 neonates (NICU-Babies) were included. We had complete data for 577 of these babies. The babies were born between 24 and 42 weeks of gestation in the years 2007–2008 and were screened in the Neonatal Unit of the Marburg University hospital. In this group, the hearing screening had been performed at or after 32 weeks of PCA. The AABR measurements showed a specificity of 93.9% (babies tested between 32 and 34 weeks of PCA), 95.8% (tested between 35 and 37 weeks), 95.9% (tested between 38 and 40 weeks of PCA) and 92.1% (tested after 40 weeks of PCA). Hearing screening yields reliable results at 32 weeks PCA. Therefore, an UNHS can be already performed before term without risking a higher rate of false positive results. However, individual factors such as cardiorespiratory and temperature stability of the baby should be considered.

Unbound bilirubin predicts abnormal automated auditory brainstem response in a diverse newborn population

OBJECTIVE

The objective of this study was to determine if plasma unbound or 'free' bilirubin concentration (B(f)) measured during the first 30 days of life is associated with subsequent abnormal hearing screening testing by automated auditory brainstem response (AABR) in a diverse population of newborns.

STUDY DESIGN

An observational study of newborns receiving AABR, plasma total bilirubin concentration (TBC) and B(f) measurements and without underlying conditions known to affect hearing was conducted. Logistic regression was used to determine associations between abnormal AABR and B(f) or TBC. The impacts of a variety of clinical factors on the regression model were also assessed.

RESULT

A total of 191 patients with birth weights and gestations ranging from 406 to 4727 g and 24 to 42 weeks, respectively, were studied. Among them, 175 (92%) had normal (bilateral PASS) AABR and 16 had abnormal AABR (6 had unilateral REFER AABR, and 10 had bilateral REFER AABR). Mean TBC was not significantly different in babies with normal or abnormal AABR, but mean B(f) was greater in the latter group (1.76 versus 0.93 microg per 100 ml, respectively, P=0.012). B(f), but not TBC, was associated with an abnormal AABR (B(f) adjusted odds ratio 3.3, 95% CI 1.8 to 6.1). Comparing receiver-operating characteristics curves, the B(f)/TBC ratio was a better predictor of an abnormal AABR than B(f) alone. Intraventricular hemorrhage was the only confounding clinical variable.

CONCLUSION

An abnormal AABR is associated with an elevated B(f) or B(f)/TBC ratio, but not the TBC alone. The prevalence of bilirubin neurotoxicity as a cause of audiological dysfunction may be underestimated if the TBC alone is used to assess the severity of newborn jaundice.