Page 48 - JCTR-11-4

Journal of Clinical and
Translational Research Female are better in otoacoustic emissions tests

detection serves as a marker of cochlear integrity and 2.1. Inclusion criteria
function. The study focused on newborns who did not require
Among the widely used methods for newborn hearing intensive care. Most participants were from the Maternity
screening (NHS) is the transient EOAE (TEOAE) test. Ward, with a few from the Intermediate Neonatal Unit.
However, research has suggested that there may be gender-
based differences in the strength of these OAE responses, 2.2. Hearing screening protocol
with female newborns exhibiting stronger reactions For newborns delivered vaginally, bilateral TEOAE
compared to their male counterparts. 1,2 measurements were typically conducted around 48 h

Studies have found significantly higher signal-to-noise after birth. In some cases, an initial screening was earlier,
ratios and response levels in females across various coinciding with the availability of the infant and the screener,
frequencies. These differences are more pronounced regardless of whether the infant was a little irritable. If
3-5
at higher frequencies. In addition to gender-based this initial screening resulted in a “refer” outcome, it was
3
differences, interaural asymmetries have been observed. repeated a few hours later, just before discharge. In most
Both sexes tend to demonstrate a right-ear advantage, such cases, the repeated screening yielded a “pass,” and that
with higher reproducibility and response levels compared result was recorded in the dataset. Infants who passed the
to the left ear. These inter-aural differences are more first screening did not undergo further testing. For infants
4-6
pronounced in males. The observed sex-based differences born through cesarean section, screening was postponed
6
in OAE responses and ear asymmetry persist from birth until approximately 72 h post-delivery, in accordance with
through at least the 1 month of life. 5 the longer postpartum stay.
st
The superior responses in EOAE tests observed in All nurses on the unit were trained to conduct
females are likely attributed to a combination of hormonal, hearing screenings and performed them during each
anatomical, genetic, and possibly evolutionary factors. shift, throughout the week, whenever workload allowed.
Female sex hormones, especially estrogens, play a crucial Tests were conducted in the newborn room with
role in enhancing the function of outer hair cells, resulting background noise kept to a minimum. Parental verbal
in stronger and more detectable OAEs. These differences consent was obtained prior to testing. Whenever possible,
are present from birth, indicating a biological basis in the measurements were taken shortly after feeding to ensure
development of the auditory system. the infant was calm and to reduce noise interference. No
pharmacological sedation was used.
Due to its speed, affordability, and proven reliability,
OAE detection serves as the foundation for many NHS 2.3. Recording equipment and protocol
programs. While most studies have focused on the All recordings were conducted using versions of the
difference in response intensity, which is usually around EchoCheck screener, based on the Intelligent Laser Otoscope
1 – 1.5 dB in favor of females, an important clinical (ILO) 88 system (Otodynamics, United Kingdom), coupled
2,7
question remains: Do these physiological differences to an ILO Ear Coupler Probe designed for neonatal use.
influence actual pass rates in neonatal hearing screening?
If so, this could have significant implications for refining The device presents a standard 1 ms nonlinear click at 84 ±
current screening protocols, potentially incorporating sex- 3 dB sound pressure level, delivered 80 times/s, and averages
specific considerations. cochlear responses across the 1 – 4 kHz frequency range.
The principal analysis focused on the 1.6 – 3.2 kHz band,
The objective of this study is to evaluate whether with the 1.6 kHz region filtered to suppress external noise.
gender-based differences exist in the pass rate of the OAE The instrument was compact and automatically adjusted
test during neonatal hearing screening, both in the general to the diameter of the external auditory canal, while light-
population and among twin pairs. emitting diode indicators verified adequate stimulus
delivery and acceptable background noise (<47.3 dB sound
2. Materials and methods pressure level on average). A “pass” indicated the presence
Data were collected between 2002 and 2023 from of TEOAEs. The Otodynamics standard default for TEOAE
healthy newborns in the maternity or neonatal ward screening with the ILO EchoCheck uses four frequency
of the Francesc de Borja Hospital. A separate analysis bands (roughly centered around 1.5, 2, 3, and 4 kHz). The
was conducted for same-sex and different-sex twins. usual pass criterion is an adequate signal-to-noise ratio
This retrospective study was approved by the ethical (commonly ≥6 dB) in at least three of those four bands
committee of the hospital on July 15, 2019, with the code with a minimum of 512 valid responses for at least 5 s. The
12/2019. duration of the test usually oscillates between 45 s and 5 min.

Volume 11 Issue 4 (2025) 42 doi: 10.36922/jctr.8416