Predicting hearing thresholds and occupational hearing loss with multiple-frequency auditory steady-state responses

Objective: An objective investigation is needed to verify the existence and severity of hearing impairments resulting from work-related, noise-induced hearing loss in arbitration of medicolegal aspects. We investigated the accuracy of multiple-frequency auditory steady-state responses (Mf-ASSRs) between subjects with sensorineural hearing loss (SNHL) with and without occupational noise exposure. Design: Cross-sectional study. Setting: Tertiary referral medical centre. Methods: Pure-tone audiometry and Mf-ASSRs were recorded in 88 subjects (34 patients had occupational noise-induced hearing loss [NIHL], 36 patients had SNHL without noise exposure, and 18 volunteers were normal controls). Main Outcome Measures: Inter- and intragroup comparisons were made. A predicting equation was derived using multiple linear regression analysis. Results: ASSRs and pure-tone thresholds (PTTs) showed a strong correlation for all subjects (r = .77 ≈.94). The relationship is demonstrated by the equation PTT=-17:5+0:94 ASSR-7:5 (in noise exposure group)+5:5 (when testedat 1000 Hz)+7:1 (when tested at 2000 Hz) +9:3 (when tested at 4000 Hz) (R ²=:89) The differences between the ASSR and PTT were significantly higher for the NIHL group than for the subjects with non-noise-induced SNHL (p < .001). Conclusions: Mf-ASSR is a promising tool for objectively evaluating hearing thresholds. Predictive value may be lower in subjects with occupational hearing loss. Regardless of carrier frequencies, the severity of hearing loss affects the steady-state response. Moreover, the ASSR may assist in detecting noise-induced injury of the auditory pathway. A multiple linear regression equation to accurately predict thresholds was shown that takes into consideration all effect factors.