Test-retest-variability of objective auditory-threshold estimation using short-pulse DPOAE level maps

 

Introduction Semi-logarithmic DPOAE input/output functions enable the determination of an estimated distortion-product threshold (EDPT) by means of extrapolation, providing a quantitative diagnosis of the cochlear amplifier (Boege a. Janssen, 2002). However, wave interference between the DPOAE components and suboptimal stimulus levels limit the accuracy of the recorded EDPTs. This work identifies the accuracy and test-retest variability of artifact-free EDPTs derived from short-pulse DPOAE level maps (Braun et al., 2019).

Methods Short-pulse DPOAEs were recorded in 20 ears at 14 frequencies f₂ = 1 – 14 kHz for 21 L₁-L₂ pairs. The representation of at least six DPOAE amplitudes as a function of L₁ and L₂ enables the derivation of EDPTs by reconstructing individual model level maps using nonlinear curve fitting. Test sessions were repeated seven times within three months. For each session, the obtained EDPTs were compared to Békésy-tracking thresholds (BT).

Results 1010 of 1332 measurable level maps (75.8 %) allow the derivation of EDPTs, which correlate significantly with BTs (r² = 0.45, p = 0.001). The pooled estimation error of the auditory-threshold estimation was 7.1 for f₂ = 1 to 10 kHz and 7.9 dB for f₂ = 1 to 14 kHz, respectively. Spontaneous OAEs may cause systematic estimation errors. Incorporating all frequencies the mean differences of EDPTs and BTs among the seven test sessions are 0.5±5.6 and 0.2±5.7 dB, respectively.

Conclusion The reconstruction of individual model level maps using curve fitting with a minimum number of six DPOAEs recorded in the L₁-L₂ space enable accurate and reproducible EDPT acquisition. Due to a variability similar to that of BTs, EDPTs represent a promising and sensitive method within the scope of ototoxicity monitoring programs.

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Publication History

Article published online:
10 June 2020

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