Thanks to state-run universal hearing screening, over 90% of newborns are screened for potential hearing loss before hospital discharge. Screening can be performed in about 9 minutes and costs $30 per child.Two tests make this possible: otoacoustic emissions (OAE) and auditory brainstem response (ABR). Both the ABR and OAE are quick and painless, and can be performed while a baby is sleeping
Otoacoustic Emissions Test
In the simplest hearing screening, OAE, a small earphone and microphone are inserted into the newborn’s ears. When sounds are played, a normally functioning ear will create an echo that can be picked up by the microphone. If a baby has hearing loss, no echo can be detected. OAE can reliably detect hearing losses above 1500 Hz, but only in the presence of outer hair cell disfunction.
Auditory Brainstem Response Test
The ABR, also known as the Brainstem Evoked Response Test (BSER), uses electrodes to detect brainwaves. As sounds are played, the test measures the brain’s response. The ABR can detect improper functioning in the inner ear, acoustic nerve, and auditory brainstem pathways associated with hearing. ABR can detect hearing sensitivity from 1000 to 8000 Hz.
Hearing Screening Is Not Perfect
It is important to note that while ABR and OAE are important tests, they are merely screens and not diagnostic tools. The problems associated with attempting to test every newborn before discharge can create high rates of false positives. Fluid or vernix in ear, which are very common in newborns, particularly in the first 24 hours of life, can cause false positive, as can an active or fussy baby. The hearing screenings can also lead to false negatives, such as when there is an isolated low-frequency (under 1000 Hz) hearing loss.
Infant hearing screening “fail” rates range between 1% and 10% at different hospitals, while actual hearing loss rates are between 0.1% and 0.6% (counting hearing loss in just one ear). Sometimes the newborn hearing screens are performed by neonatal staff that are minimally trained and have a myriad other responsibilities; anecdotal suggests that hospitals using dedicated audiology technicians have significantly decreased rates of false positives.
Screening only high-risk infants would result in much fewer false positives, and much less needless worry for some parents. Still, screening all infants nearly doubles the number of cases detected and, because of increased early intervention opportunities, results in lifetime cost savings.
