Wideband absorbance in Australian Aboriginal and Caucasian neonates

Despite the high prevalence of otitis media in Australian Aboriginal infants and children, the conductive mechanism of the outer and middle ear of Aboriginal neonates remains unclear. Differences in characteristics of the conductive pathway (outer and middle ear) between Aboriginal and Caucasian neonates have not been systematically investigated by using wideband acoustic immittance measures.

The objective of this study was to compare wideband absorbance (WBA) in Australian Aboriginal and Caucasian neonates who passed or failed a screening test battery containing high-frequency tympanometry and distortion product otoacoustic emissions (DPOAEs).

A cross-sectional study design was used. The mean WBA as a function of frequency was compared between Aboriginal and non-Aboriginal neonates who passed or failed the test battery.

A total of 59 ears from 32 Aboriginal neonates (mean age, 51.9 h; standard deviation [SD], 18.2 h; range, 22-86 h) and 281 ears from 158 Caucasian neonates (mean age, 42.4 h; SD, 23.0 h; range, 8.1-152 h) who passed or failed 1000-Hz tympanometry and DPOAEs were included in the study.

WBA results were analyzed by using descriptive statistics and t tests with Bonferroni adjustment. An analysis of variance with repeated measures was applied to the data.

Aboriginal and Caucasian neonates had almost identical pass rates of 61%, as determined by the test battery. Despite the apparently equal pass rates, the mean WBA of Aboriginal neonates who passed the test battery was significantly lower than that of their Caucasian counterparts at frequencies between 0.4 and 2 kHz. The mean WBA of Aboriginal neonates who failed the test battery was significantly lower than that of their Caucasian counterparts who also failed the test battery at frequencies between 1.5 and 3 kHz. Both Aboriginal and Caucasian neonates who failed the test battery had significantly lower WBA values than their counterparts who passed the test battery.

This study provided convincing evidence that Aboriginal neonates had significantly lower WBA values than their Caucasian counterparts, although both groups had equal pass rates, as determined by the test battery. Although the two ethnic groups showed significant differences in WBA, the factors contributing to such differences remain undetermined. Further research is warranted to determine the factors that might account for the difference in WBA between the two ethnic groups.