Simultaneous combined examination of changes in hresholds estimates and short-pulse DPOAE during serial hearing measurements.

Serial monitoring of behavioral thresholds and distortion-product otoacoustic emissions (DPOAEs) detect progression of cochlear damage. Recently, estimated distortion-product thresholds (EDPTs) based on short-pulse DPOAE level maps provided a reliable quantitative and objective estimate of hearing loss that may be used in serial measurements.They combine a short-pulse stimulus paradigm to reduce DPOAE interference effects and an individually optimum stimulus-intensity paradigm, which when combined allow objective, accurate, and reliable threshold estimates. For the diagnosis of damage to the cochlear amplifier, measurement methods are needed that exhibit the lowest possible variability and can thus detect changes in hearing sensitively. Here, we investigate the effect of a combined examination of changes in behavioral thresholds, EDPTs, and DPOAE levels on test-retest reliability. Behavioral thresholds were recorded using modified Békésy tracking audiometry (TA) seven times with f₂ = 1–14 kHz in 20 ears with normal hearing. Reconstruction of DPOAE growth behavior as a function of L₁,L₂ allowed derivation of an EDPT for each frequency. Test-retest reliability was determined using average differences between test sessions. For the simultaneous combined observation, hearing-threshold elevations were correlated with DPOAE-level reductions. Considered individually, TA and EDPT showed SDs of differences of 6.3 dB and 5.7 dB, respectively. The combined consideration of hearing-threshold changes by TA and EDPT reduced the SD of differences to 4.6 dB. Further improvement was found by also including the DPOAE-level changes with an SD of 3.9 dB. To detect actual pathological threshold shifts, the combined analysis of the three methods may be promising in the future.