Skip to content

LESSON 173

Screening protocols

Year 2
Spring semester
Hearing Screening
Screening programs
Duration: 11:15

In newborn hearing screening, which test is used, for which baby and in what order? In this lesson we cover what OAE and AABR assess, the well-baby and intensive care protocols, two-stage screening, and the rules behind pass and refer decisions.

Watch on YouTube

Follow along

Hello, and welcome to the AIHEAR Audiology Academy.
In this lesson we will learn the protocols used in newborn hearing screening, separating well babies from intensive care babies.
We will also see how pass and refer decisions are made and which protocol errors are common.
Last lesson we met the two core screening tests: otoacoustic emissions, or OAE, and automated auditory brainstem response, or AABR.
Before choosing a protocol, let us be clear about which part of the auditory pathway each test assesses.
Sound passes through the ear canal, is conducted by the middle ear and becomes a neural signal in the cochlea.
OAE reflects the ear canal, the middle ear and the function of the outer hair cells in the cochlea.
So if sound reaches the cochlea and the outer hair cells are working, an OAE response can be recorded.
AABR also covers the inner hair cells, the auditory nerve and the brainstem pathway.
This difference is decisive for auditory neuropathy spectrum disorder, or ANSD, in which neural transmission is disrupted.
In ANSD the outer hair cells often work, so OAE can be normal while AABR shows no response.
Screening devices give the result automatically with a statistical algorithm, with no need for expert interpretation.
In OAE screening, the device checks whether the response is far enough above the noise floor in certain frequency bands.
How many bands must show a response, and how large the difference must be, vary by device and program.
In AABR screening the stimulus is usually 35 dB nHL, or normalized hearing level; the device looks for a brainstem response at this level.
The Joint Committee on Infant Hearing, or JCIH, targets permanent losses averaging 30 to 40 decibels or more in the speech frequencies.
So milder losses and some losses in a narrow frequency region can pass the screening.
A common approach in well-baby nurseries is two-stage screening, which uses the two technologies one after the other.
OAE, which is quick and low cost, is done first; a baby who does not pass OAE gets AABR, usually before discharge.
Vernix and middle ear fluid, common reasons for an OAE refer, affect the AABR result less.
So in many protocols, a baby who passes AABR is considered to have passed the screening.
A baby who also does not pass AABR is referred for diagnostic audiological evaluation.
Two-stage screening clearly lowers the referral rate and spares families unnecessary worry.
But studies have shown that a small share of babies who did not pass OAE but passed AABR were later found to have permanent loss.
Most of these losses were mild, that is, below the AABR screening level.
So even in a two-stage protocol, the family is told to keep watching the child's hearing and speech development.
For well babies, JCIH accepts screening with either OAE or AABR; programs choose based on their own conditions.
The advantages of an OAE-only protocol are speed, low cost and easy use.
But the refer rate may be higher in the first days because of vernix and fluid.
An AABR-only protocol may give a lower refer rate, since it covers the neural pathway and is less affected in the first days.
On the other hand, it needs electrodes and disposables, and takes a little longer to perform.
The two-stage protocol, which uses OAE and AABR together, combines the strengths of both methods.
Whatever protocol is chosen, trained staff and regular quality monitoring determine how reliable the result is.
Birth numbers, staffing, available equipment and how long mothers stay in hospital also play a role in the choice.
In the neonatal intensive care unit, or NICU, the protocol is different.
JCIH recommends that babies who stay in intensive care for more than five days be screened with AABR.
This five-day cutoff appears in the same way in both the 2007 and 2019 JCIH position statements.
This is because these babies have a higher risk of ANSD due to causes such as prematurity, hyperbilirubinemia and hypoxia.
The OAE response shown in the drawing can also be recorded in a baby with ANSD, as long as the outer hair cells are intact.
So screening with OAE alone can classify a baby with ANSD as a pass.
Rescreening a baby who did not pass AABR with OAE and counting it as a pass is not recommended.
NICU babies who do not pass AABR are referred directly to an audiologist for rescreening and, if needed, diagnostic ABR.
A baby who passed screening may be readmitted in the first month for a condition linked to hearing loss.
Hyperbilirubinemia, or severe jaundice, that requires exchange transfusion is one example.
Culture-positive sepsis, a severe infection confirmed by bacteria growing in the blood, is another.
JCIH recommends repeating the hearing screening before discharge in these babies.
This is because these conditions can cause a loss that appears after the birth screening result.
Even if the earlier screening result was a pass, a new risk calls for a new evaluation.
Not passing in one ear is also a refer result, and the baby is referred for rescreening or diagnosis per the protocol.
This result is not trivial, because unilateral loss can also affect the child's development.
At rescreening, testing both ears is recommended, even if only one ear did not pass the first screening.
Testing again and again in one session until a pass appears raises the chance of a false pass by luck.
So programs limit the number of attempts per session.
Which ear did not pass is also clearly written in the record and in the written information given to the family.
The date, method and result of every attempt are recorded; this record is the basis of the tracking system.
Now let us put the protocols side by side.
For well babies, the first screening uses OAE or AABR; a baby who does not pass is rescreened.
In the two-stage protocol, a baby who does not pass OAE gets AABR; one who also does not pass AABR is referred for diagnosis.
Babies in intensive care for more than five days are screened with AABR; if they do not pass, they go straight to an audiologist.
In a baby readmitted in the first month for a condition linked to hearing loss, screening is repeated before discharge.
Details may vary from country to country and program to program, but the basic logic is the same.
The success of a protocol also depends on clear and consistent information for the family.
Before screening, the family is briefly told what the test is, that it is painless and that it is quick.
With a pass, the family is told that this shows a response at the screening level.
Because hearing can change later, they are asked to keep watching responses to sound and speech development.
With a refer, it is clearly stressed that the result is not a diagnosis and only means more testing is needed.
It is also explained why the follow-up matters, since some babies who do not pass do have a real loss.
If possible, the rescreening or diagnostic appointment is given in writing before the family leaves the hospital.
A tip from the field: the weakest link in a screening protocol is often not technical but communication.
The family of a baby who did not pass in one ear may skip the appointment because the other ear is fine.
The family of a baby who passed a two-stage protocol should also know that screening can miss mild losses.
Explain briefly and concretely how they can watch the baby's responses to sound and speech development.
Give them in writing where to go if they have concerns.
In this lesson we saw that OAE assesses the pathway up to the cochlea, while AABR assesses it up to the brainstem.
For well babies, OAE, AABR or a two-stage protocol using both in sequence can be used.
Babies in intensive care for more than five days are screened with AABR because of the risk of ANSD.
Not passing in one ear is also a refer result; at rescreening both ears are tested together.
Test yourself: which test should be used to screen a baby who spent ten days in intensive care?
The correct answer is B: with AABR.
These babies have a higher risk of auditory neuropathy; since OAE can be normal, AABR, which also covers the neural pathway, is needed.
In the next lesson we will look at babies who need monitoring even after passing screening: risk indicators and late-onset loss.
Subscribe to the channel so you never miss a new lesson. See you soon!

Keywords

Click a keyword to search all lessons for that term.

Prerequisites

Comments

Questions and comments appear after approval.

No comments yet. Be the first to comment.