The Effect of probe placement on DPOAE amplitudes at high frequencies.

Abstract

Abstract Background: The high-frequency distortion product otoacoustic emission (DPOAE) is the test that examines the function of the outer hair cells at frequencies above 8 kHz. The sensorineural hearing loss (SNHL) that may result from noise exposure or ototoxic medication can be monitored using the high-frequency DPOAE. Objective: The aims of this study were to explore: 1) the effect of the depth of insertion of the probe on the DPOAE amplitude at 2 and 10 kHz; 2) the test–retest reliability of the DPOAE amplitudes and hearing threshold level HTL at 2 kHz and 10 kHz with and without the removal and replacement of the probe/insert-phone; 3) the test–retest error of DPOAEs related to that of a hearing threshold at 2 and 10 kHz. Method: 24 participants aged from 18 to 45 and within normal hearing thresholds (< or = 20 dB HL) at the conventional frequencies (250Hz-8 kHz) were involved in this experiment. Both high-frequency DPOAE and HTL were measured at two different depths of insertion (deep and shallow) and two frequencies (2kHz and 10kHz). Then the measuring of both tests was repeated with and without the replacement of the probe or insert-phone to assess the test–retest reliability. Results: The depth of insertion had no effect on the DPOAE amplitudes, while the HTL was affected by the depth of insertion at both 2 and 10 kHz. Then, in 15 participants, the average of the test–retest error of the DPOAE amplitude with replacement at 2 kHz was higher compared with the average of the test–retest error of the DPOAE amplitude without replacement, whereas it was higher in 18 participants at 10kHz. For HTL, at 2kHz, no differences in test–retest error were recorded between the two conditions (with and without replacement) for 11 participants at 10 kHz, and no differences in this test–retest error were recorded for 14 participants. There was no statistically significant correlation between the test–retest error for DPOAEs and HTLs. Conclusion: The finding of this study suggests that at the 2kHz and 10kHz, the DPOAE amplitudes are not affected by the depth of insertion; in contrast, the HTLs are affected by the depth of insertion. Most of the participants’ average of the test–retest error of the DPOAE amplitude with replacement revealed a higher retest error value than the retest error value for measurement without replacement. There was no correlation between the test–retest error for DPOAEs and HTLs. There is a need to further investigate the high-frequency DPOAE.