Breakdown of primary frequencies used in pediatric hearing screening with distortion-product otoacoustic emissions (DPOAEs)

Abstract

Background

DPOAEs are acoustic energy within the external auditory canal (EAC) arising from the non-linear interaction within the cochlea; of 2 pure tones presented simultaneously; of primary frequencies f1 and f2. DPOAEs are recorded in nearly any normal-hearing subject and in patients with hearing loss up to 50 dBHL while recordings may be deceiving in the presence of severe to profound hearing loss.

Objective

To determine the intensity levels of f1 and f2 at which DPOAEs truly reflect the active metabolic processes within the cochlea.

Setting

University Hospital

Study

Prospective

Methods

One-hundred and forty ears were categorized into three groups; A (n = 50), B (n = 50) and C (n = 40); according to subjects' age (12 to 18, 2 to 12 and <2 years, respectively). A fourth group D was included; which entailed recordings from a dummy cavity simulating a child’s external auditory canal. Each group was further subdivided into two subgroups according to hearing levels; either normal or severe to profound hearing loss. DP-grams were interpreted at 3 points/octave steps for all groups and reviewed as ‘Pass’ or ‘Fail’ according to set criteria. Stimulus levels were adjusted such that L1 exceeded L2 by 10 dB. Start levels for L1 and L2 were 80 and 70 dBSPL. Levels were reduced simultanueously in 5 dB steps for the following recordings; to reach 65 and 55 for the last recording.

Results

Using the higher three stimulation levels, all subgroups had ‘Pass’ DP grams. On using the last and lowest recording level, only subgroups of normal hearing ears had ‘Pass’ DP grams; while subgroups of ears with sensorineural hearing loss (SNHL) demonstrated ‘Failed’ DP grams at all frequencies.

Conclusions

For audiometric screening purposes, DPOAEs show to be rather insensitive to hearing loss at higher stimulation levels and may reveal false positive results.

Keywords:

• DPOAE
• False positive
• primary frequencies
• stimulation levels

Disclosure statement

No potential conflict of interest was reported by the author(s).