Accuracy and Time Efficiency of Two ASSR Analysis Methods Using Clinical Test Protocols

Background: The number of commercially available evoked potential systems implementing multiple-frequency auditory steady-state response (ASSR) techniques has increased over the last several years. The majority of data in the multiple-frequency ASSR literature have been obtained using time-domain averaging and Fast Fourier Transform (FFT) techniques with F-test statistical analysis. Another commercially available analysis method has been introduced using an adaptive filtering algorithm called the Fourier Linear Combiner (FLC). No previous investigation has evaluated the performance of the FLC method, nor compared the two techniques. In addition, there is a need for evaluation of clinical protocols for ASSR testing using these available commercial systems that balance time efficiency and accuracy in estimating threshold.

Purpose: (1) To determine whether ASSR thresholds, the relationship between ASSR and behavioral thresholds, and clinical test time are affected by the ASSR analysis method when comparing two commercially available systems for multiple-frequency ASSR. (2) To investigate the use of clinical ASSR test protocols of varying recording length, and the effect on accuracy and time efficiency, using these two commercially available analysis methods.

Research Design and Study Sample: ASSR threshold searches were completed on a group of 20 normal-hearing and 20 hearing-impaired adult participants using two different analysis methods, FFT and FLC, under separate, independent, tests as well under simultaneous recording conditions.

Data Collection and Analysis: Three experiments were completed: (1) independent assessment of ASSR thresholds using the FFT and FLC methods separately, (2) simultaneous recording of ASSR for both the FFT and FLC method, and (3) an automated threshold search protocol using the FLC method. Variables analyzed for Experiments 1 and 3 included ASSR thresholds, the difference between ASSR and behavioral threshold, and total test time. For Experiment 2, the number of detected ASSRs per method, the agreement between methods, and the time per detected ASSR were evaluated.

Results and Conclusions: ASSR thresholds and the relationship between ASSR and behavioral thresholds were found to be in line with those reported in the literature for multiple-frequency ASSR for both the FLC and FFT methods. ASSR thresholds were found to be significantly higher for the FLC method for the low frequencies, but not for the high frequencies, when tested independently. Correlations between ASSR and behavioral thresholds, however, were found to be the same across methods. Overall, it did not appear that either analysis method held an advantage in terms of accuracy or overall test time in independent comparisons using the protocol implemented in the current study. The time benefits of an automated protocol were significant, although with compromised test accuracy. The results of this study suggest critical clinical decision making is a necessary part of the ASSR protocol in order to decrease false positive and false negative responses and to increase overall efficiency.

Key Words

Analysis method - auditory evoked response - auditory steady-state response - hearing threshold - objective audiometry - recording time