This study examined the ability of click auditory brainstem response (ABR) undertaken below the age of 6 months (from expected date of delivery) to differentiate between conductive and sensorineural hearing loss (SNHL), using the latency of wave V measured 20 dB above threshold.
Subjects were recruited if they had an ABR threshold of ≥ 40 dB nHL and ≤ 70 dB nHL in one or both ears measured below the age of 6 months and they had also attended follow-up appointments for behavioral assessment of their hearing in which the type of hearing loss had been confirmed. Forty-five children (84 ears) with SNHL, 82 children (141 ears) with temporary conductive hearing loss (TCHL), and 5 children (10 ears) with permanent conductive hearing loss (PCHL) were recruited. The differences between mean wave V latencies measured 20 dB above ABR threshold were examined using the independent t-test for the groups of cases with SNHL, TCHL, and PCHL. Signal-detection theory was used to examine the relationship between sensitivity and specificity when the latency of wave V 20 dB above threshold was used to identify the presence of SNHL. Receiver operating characteristics were generated and the coordinates of the curve examined for the best compromise between sensitivity and false-alarm rate. The specificity, positive predictive value, and probability of missing a true case were determined for the most promising criteria.
There were significant differences between the two groups with SNHL and TCHL. The mean latency of wave V 20 dB above threshold was 1 msec shorter in those with SNHL compared with those with TCHL. There were significant differences between children with PCHL and SNHL but no difference between those with PCHL and TCHL. When a criterion of < 7.6 msec was chosen to predict the presence of SNHL the test sensitivity was 0.98, test specificity 0.71, and positive predictive value was 0.66. Nine out of 10 of those with a latency 20 dB above threshold of < 7.0 msec had an SNHL.
The latency of wave V 20 dB above threshold measured using click ABR is a useful indicator of the type of hearing loss in babies referred from newborn hearing screening.