Hearing Screening: OAE vs Automated ABR

This video explores the clinical utility of otoacoustic emissions (OAE) as a newborn hearing screening tool and compares OAE with automated ABR. You can read the full transcript below.

Benefits of early hearing loss detection and intervention

In newborn populations, it is estimated that 1-3 per 1000 births will have some form of hearing loss. This rate is even higher in neonatal intensive care units. Earlier detection of hearing problems and the resulting intervention lead to better speech and language development, communication, learning abilities, and social and emotional outcomes.

Global implementation of newborn hearing screening

Many countries across the globe already implement newborn hearing screening programs. Some programs have been established for decades while others are still in their infancy. Common across all programs are the main test types used to screen: otoacoustic emissions and automated auditory brainstem responses.

Otoacoustic emissions

Otoacoustic emissions are found in normally functioning ears when a sound is presented to the ear. Resulting sounds can be recorded coming back out. These sounds are produced by the ear itself and are known as otoacoustic emissions.

To obtain an emissions recording, a small probe needs to be placed into the ear and a sound is presented. The OAE equipment then records the response from the ear and presents it on screen for interpretation. The test environment and baby need to be very quiet as the recorded emissions are very small.

Advantages of OAE testing

Otoacoustic emissions are relatively cheap and quick to perform. They also require minimal training of staff. The equipment is often small and portable, giving a pass or refer result in under 30 seconds per ear.

Disadvantages of OAE testing

One disadvantage of OAE testing is that there is a higher likelihood compared to automated ABR testing that an ear does not pass the test even though no serious hearing problem is present in the ear. This result can occur due to fluid in the ear canal, if the child is too unsettled during the test, of if there's too much acoustic noise.

Another disadvantage of OAE testing is that the emissions are generated by the cochlea. This test does not measure higher-level structures in the auditory pathway. Therefore, the OAE test cannot be used to estimate the function of the hearing nerve or the brainstem.

Automated ABR

Automated ABR is the other test of hearing which is commonly used in newborn hearing screening programs. Electrodes are required to be placed on the baby's scalp and ear cups or probes placed into the ear to deliver the sound. The ABR equipment then records neural activity from the electrodes and provides a pass or refer result on the screen.

Advantages of automated ABR testing

Its advantages are that the results are more robust than in OAE testing with fewer ears being referred. This is because automated ABR is more forgiving compared to OAE towards small amounts of fluid.

Automated ABR also tests structures higher up in the auditory pathway. We are therefore given a much better idea of how the child's whole auditory system is functioning and not just the cochlea.

Disadvantages of automated ABR testing

Automated ABR's main disadvantage is that the equipment used is more expensive and more training is needed for staff to carry out the tests. There are more costs involved of disposables being used and it takes more time to perform the test.

As with OAE testing, the room noise and noise from the baby can adversely affect the result.

OAE vs automated ABR

In light of these two tests and their advantages and disadvantages, countries might, depending on local circumstances, decide to implement a newborn hearing program with one, the other, or a combination of both tests.

The most common setup is that the cheaper otoacoustic emission is used for the initial screening. If the baby does not pass this test or refers, they are then re-screened using the automated ABR.

The importance of follow up for referred babies

It is important to note that follow-up is essential for babies who have referred on their screening tests. Some publications discuss the lack of follow-up or lack or resources available for adequately re-testing referred babies.

Often, babies are discharged from the hospital before the second screen, and the responsibility is given to the parents or caregivers of the child to bring the baby back to the hospital to be re-tested. This has the risk to miss some babies with hearing loss, where the initial benefits of early detection can be lost.