DOI: 10.1177/0194599812467429

No sponsorships or competing interests have been disclosed for this article. Objective. We aimed to determine whether abnormalities in outer hair cell (OHC) function were related to tinnitus through interaural comparison of distortion product otoa-coustic emissions (DPOAEs). Study Design. Cross-sectional study. Setting. Tertiary care university teaching hospital. Participants. Twenty-seven patients with unilateral tinnitus and pure-tone average of both ears 25 dB hearing loss (HL) at 500, 1000, 2000, and 4000 Hz were included. Subjects and Methods. Pure-tone thresholds observed at 500 to 16,000 Hz and DPOAE amplitudes at f2 frequencies of 1001 to 6348 Hz were compared between the tinnitus ears and nontinnitus ears in patients with unilateral tinnitus. Results. The pure-tone averages (13 6 6 dB HL) in the non-tinnitus ears were similar to those (15 6 6 dB HL) in the tinnitus ears. There were no differences in pure-tone averages at all frequencies tested. While the DPOAE ampli-tudes measured at f2 frequencies of 1001 to 3174 Hz in tin-nitus ears were not different from those in the nontinnitus ears, the tinnitus ears showed significantly reduced DPOAE amplitudes when compared with the nontinnitus ears at fre-quencies of 4004 to 6348 Hz. Conclusion. OHC dysfunction was correlated with tinnitus at high frequencies, and DPOAE amplitudes can provide addi-tional information about cochlear dysfunction, which is com-plementary to pure-tone audiometry