Click-evoked oto-acoustic emissions in 1036 ears of healthy newborns.

Click-evoked oto-acoustic emissions (EOAEs) were recorded in 1036 ears of healthy newborns and in 71 normal-hearing adult ears. Newborns aged between 3 and 238 h were examined in a separate but not silent room of the obstetric ward. The adults were tested in a quiet but not sound-treated room. The recordings were more difficult in the newborn than in the adult, which was mirrored in recording parameters such as the time required for measurement (up to 7 min in newborns vs. 1-2 min in adult ears). Recording was always successful in adults, while retests were necessary in 4% of newborns. Also the artefact-rejection level and the stimulus stability were more favourable in adults. Still, EOAE recording for screening purposes in newborns seems feasible. Response levels in newborns (range 1.6-38.6; mean 20.2 dB SPL) appear to be higher than in adults (range 2.7-20.6; mean 12.8 dB SPL). The overall prevalence of EOAEs in newborns amounted to 93.4% and appeared to be age related. It rises from 78% in ears from newborns younger than 36 h to 99% in ears of newborns older than 108 h. This rise may be related to the middle ear clearance of amniotic fluid in the first days post partum. The prevalence in newborns older than 3-4 days is comparable with the prevalence of 97.2% in adults. Therefore, newborns should not be screened before the age of 4 days. In search of an objective EOAE detection variable, the prevalence of EOAEs for different age groups was calculated for various criterion values of reproducibility. These prevalences were compared to subjectively scored EOAE prevalences in the same age groups. A reproducibility criterion of about 50% appears to be useful for mass screening in newborns.