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DSL v5 and Compatibility with ABR Assessment
Audiologists working with Early Hearing Detection and Intervention (EHDI) programs are assessing the hearing abilities of very young infants using electrophysiologic procedures (American Speech Language and Hearing Association, 2004; Joint Committee on Infant Hearing, 2000). The ABR measurement has been shown to be feasible for estimating hearing thresholds in young infants (Stapells, 2000a; 2000b; American Speech Language and Hearing Association, 2004; Joint Committee on Infant Hearing, 2000). While much research has focused on the development of frequency-specific (FS) ABR procedures for threshold estimation in infants, little work has been done to investigate how ABR data are to be applied in hearing aid prescriptive software. In DSL v5, clinicians may enter threshold data referenced to normalized HL (nHL) or estimated HL (eHL). The interested reader is directed to Bagatto et al. (2005) for a detailed description of nHL and eHL-referenced electrophysiologic data. Many studies have shown that ABR threshold estimates are higher than behavioral thresholds. For this reason, a correction must be applied to the ABR threshold estimation to better predict the behavioral threshold that will be used for calculating the hearing aid prescription. It is important for the clinician to know if their ABR equipment has behavioral corrections imbedded in it or not. If the correction has not been imbedded in the system, a correction needs to be applied to the nHL value to provide a better estimate of behavioural thresholds. In this case, frequency-specific threshold estimates are entered in nHL, and corrections will be applied within the DSL software to convert the nHL data to eHL. These corrections can either be default values that are stored within the software, or the clinician can enter their own custom nHL to eHL correction values. The default values are appropriate for use with FS-ABR procedures that comply with the calibration and stimulus parameters outlined in Bagatto et al. (2005). If the threshold estimates have already been corrected to an eHL reference by the clinician or if the ABR system has the corrections imbedded in it, no additional correction is required and is therefore not applied. Clinicians with these situations should choose ABR (eHL) and enter the data. Clinicians who assess the hearing of infants using ASSR procedures are cautioned to ensure that the ASSR system is applying an nHL to HL correction that is valid for use with infants who have hearing loss (Stapells, Herdman, Small, Dimitrijevic and Hatton, 2005). In this case, data may be entered directly into DSL v5 by using the eHL reference.
