Otoport OAE+ABR
User Manual for Otoport DP+TE model
199
Mode of operation
Sensitivity of the Otoport OAE+ABR for ABR screening
The sensitivity of the Otoport OAE+ABR for ABR screening was measured
using 349 recordings from 30 neonates (3 days to 4 weeks old). The
instrument was configured to deliver its short chirp stimulation at a level
of 35dBnHL and at a rate of 52 per second. However for the purpose of
these recordings the stimulating probe was fitted to a closed cavity next
to the baby’s ear, so that no ABR was actually generated. Additionally the
real-time electrical signals received from the electrodes on the baby were
digitally recorded through the device for durations of many minutes. These
electrode signals were then replayed at their original level into the Otoport
OAE+ABR and a total of 3257 ABR further tests were run to ensure all
statistical combinations of noise and instrument timings were represented.
Each of the 3257 ABR test results were evaluated by each of the four pass
criteria (PC1-4). The results below describe the rate of false (artefactual)
passes obtained when a realistic wide range of neonate electrode noise
signals (i.e. from sleeping to restless) is processed by the device. As no
acoustic stimulation actually reached the ear, no real ABR was present, so
all ‘passes’ are false.
Very high sensitivity of the instrurment is demonstrated with each pass
criteria. Pass criteria PC2 and PC3 showed the highest sensitivity,
exceeding 99.9%. This would be expected because PC2 and PC3 require
that the response correlates with the neonate ABR template. PC1 and PC4
only require that an Fsp statistical criteria is met and so showed a slightly
lower sensitivity of 99.79%.
Since the acoustic stimulus was not delivered to the ear, this sensitivity
data is valid for all stimulus settings and levels up to a level where electrical
artefacts from the probe might create an artefactual pass. Rigorous tests
showed that no artefactual passes occurred due to electrical stimulus
artefacts up to the maximum stimulus level of the instrument, for both click
and short chirp stimuli.
Pass Criteria
PC1
PC2
PC3
PC4
Tests
3257
3257
3257
3257
Passes
7
2
2
7
Pass probability (%)
0.21
0.06
0.06
0.21
CI(Hi) (%)
0.44
0.22
0.22
0.44
CI(Low) (%)
0.09
0.01
0.01
0.09
Sensitivity (1 - Pass prob)
99.79%
99.94%
99.94%
99.79%
Confidence Interval (CI) measurements are given at 95%.