Click-evoked oto-acoustic emissions in very-low-birth-weight infants: a cross-sectional data analysis

For the purposes of studying the phenomenon of evoked oto-acoustic emissions (EOAEs) in very-low-birth-weight (VLBW) infants, and the conditions affecting the utility of EOAE ear screening in this population, click EOAEs were repeatedly recorded in ears of 144 VLBW infants, at different postconceptional ages of the infants and at two different test sites, i.e. in the neonatal high-care unit (ward), or at the neonatal outpatient clinic. The postconceptional age of the infants examined in the ward was 30-49 weeks and 37-66 weeks for the infants examined at the outpatient clinic. Overall 840 recording attempts were done. In the ward 86% of these attempts (388) were successful against 60% (of 452 attempts) at the outpatient clinic. In the latter group of infants the success rate of recording was only 33% at the corrected age of 6 months, which is significantly less than the 66% until the corrected age of 3 months. For a cross-sectional analysis of age effects one ear of each successfully recorded infant was selected. Analysis of the 127 successful recordings revealed that the EOAE prevalence was 71% in the ward (54% for infants receiving extra oxygen per naso) and 91% at the outpatient clinic. Compared with healthy newborns, VLBW infants are much more difficult to test, especially at the outpatient clinic. However, the EOAE prevalence at this test site is the highest and approaches that in healthy newborns. At the outpatient clinic response levels of EOAEs recorded approach levels found in healthy newborns. The higher success rate of recording in the ward and the lower EOAE prevalence are two counteracting factors as to the utility of EOAE-based ear screening of VLBW infants.