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Repeatability of Click-Evoked Otoacoustic Emission-Based Medial Olivocochlear Efferent Assay

Mishra, Srikanta K.; Lutman, Mark E.

doi: 10.1097/AUD.0b013e3182944c04
Research Articles

Objectives: Otoacoustic emissions–based efferent assays are evolving to become a part of auditory diagnostics. The wide range of clinical applications, such as assessment of auditory neuropathy, auditory processing disorders, learning disability, monitoring success in auditory intervention and others illustrate the significance of this measurement. Defining the procedure’s test–retest repeatability is of critical importance, to allow for distinction between measurement deviations and true physiological or pathological changes. The purpose of this study was to assess the repeatability of a click-evoked otoacoustic emission–based (CEOAE) test of the medial olivocochlear (MOC) reflex in normal-hearing (NH) adults.

Design: Test–retest data were collected from 35 NH young adults in two distinct test sessions separated by 1 to 4 days. CEOAEs were recorded without and with contralateral acoustic stimulation (CAS; 35 dB SL). Three indices of the MOC reflex were computed: CAS-induced (a) absolute changes in CEOAE amplitude, (b) normalized changes in CEOAE amplitude, and (c) changes in CEOAE input–output functions. Repeatability of these indices was assessed by a three-layered approach, which consisted of Bland-Altman plots, coefficient of reliability (Cronbach’s α), and analysis of variance.

Results: Analyses indicated good repeatability of three CEOAE-based MOC reflex indices. A two-way analysis of variance of the indices demonstrated no significant difference between test and retest. Normalized index showed similar repeatability as other indices. CEOAE signal to noise ratio did not seem to vary between test sessions. Notably, CAS caused a decrease in CEOAE input–output functions slope in a majority of participants (n = 29).

Conclusions: The present study is the first to elucidate the intrasubject variability of absolute and normalized indices of the MOC inhibitory effect. Although the measurements were conducted under realistic conditions resembling the clinical setting, repeatability was generally good in NH adults. For MOC reflex test, the signal to noise ratio of 6 dB for recording CEOAEs seems to be a recommendable criterion when considering practicability and measurement quality in clinical conditions. The present findings exemplify the suitability of CEOAE-based MOC assay as a monitoring tool of medial efferent status over time. The data are intended to assist clinicians and scientists alike in the accurate interpretation of CAS-induced CEOAE changes in the test–retest situation.

Click–evoked otoacoustic emissions (CEOAEs)–based efferent assay has both scientific and clinical significance. Defining test–retest repeatability of a CEOAE–based test of the medial olivocochlear (MOC) reflex is crucial to distinguish between variance due to measurement deviation and true physiological or pathological changes. This study assessed the repeatability of a CEOAE–based MOC reflex test in normal–hearing adults. The results suggest that the CEOAE-based assay of MOC reflex produces a clinically acceptable test–retest repeatability in normal–hearing adults.

Institute of Sound and Vibration Research, Hearing & Balance Center, University of Southampton, Southampton, United Kingdom.

ACKNOWLEDGMENTS: This research was supported by a grant (EMFnEAR) from the European Commission, Directorate-General for Health and Consumer Protection (Grant No. 2004127) and a Rayleigh scholarship from the Institute of Sound and Vibration Research, University of Southampton.

The authors declare no conflict of interest.

Address for correspondence: Srikanta K. Mishra, Department of Communication Sciences and Disorders, College of Communication, Butler University, 4600 Suset Avenue, Indianapolis, IN 46208. E-mail: skmishra@butler.edu

© 2013 by Lippincott Williams & Wilkins