otometrics AccuScreen ABR, User Manual

Page: 55 / 110

Otometrics
55
Tests
The ABR test
Test result REFER (Test referred)
If the infant moves or is sucking or crying during the test, this may result in too much
electrical noise. Other electrical appliances and fluorescent lighting in the vicinity can
also cause electrical interference.
A good indication of this is if the ABR bar on the display is close to the PASS (Test
passed) criterion but does not result in a PASS . If this is the case, try to improve test
conditions and repeat the test.
Consequently, before you refer the patient for further follow-up, it is recommended
that you improve test conditions and repeat the test:
• Does the probe fit well in the ear canal?
• Are the electrodes placed correctly and fit properly? Even if the device accepts the
impedance values, it is often worth while to attempt to reduce impedance values
and particularly the impedance differences. The noise in the electrode cable
depends strongly on the impedance values.
If the result is a PASS (Test passed) , only the graph
is shown.
• A PASS (Test passed) indicates that an audi-
tory brainstem response to a 35, 40 or
45 dB nHL broadband stimulus was
detected.
This method mainly tests the frequencies
from 2 to 4 kHz, which carry the most
important acoustic information for speech
development.
• A PASS (Test passed) result ensures that a significant hearing loss in these fre-
quencies can be ruled out with 99.5% confidence.
If the result is a REFER (Test referred) , the
detailed results are shown immediately below the
graph.
• A REFER (Test referred) may indicate a sig-
nificant hearing loss.
• A REFER (Test referred) may also be the
result when too much electrical noise drowns
out the response.