When we evaluate the success of a hearing aid fitting, or the effectiveness of new amplification technology, self-report data occupy a position of critical importance. Unless patients report that our efforts are helpful, it is difficult to justify a conclusion that the intervention has been successful. Although it is generally assumed that subjective reports primarily reflect the excellence of the fitted hearing aid(s) within the context of the patient’s everyday circumstances, there is relatively little research that assesses the validity of this assumption. In previous work, we have reported some contributions of the service delivery setting (private practice versus public health) to self-report outcomes. The purpose of the present investigation was to assess the relative contributions of patient variables (such as personality and hearing problems) and amplification variables (such as soft sound audibility, gain and maximum output) to self-reports of hearing aid fitting outcomes.
A cross-sectional survey of 205 patients was conducted with cooperation of eleven Audiology clinics. All subjects were recruited when they were seeking new hearing aids. Before the hearing aid fitting, measurements of personality and response bias were made, as well as measures of hearing problems and expectations about amplification. At the fitting, traditional verification data were measured including sound field thresholds, preferred gain for conversation, and maximum output. Six months after the fitting, a set of 12 standardized self-report outcomes was completed. Analyses concerned: (1) the associations among personality, response bias, and self-reports about hearing problems that are available before the hearing aid fitting, and (2) the associations of these precursor variables, and fitting verification data, with self-report data assessing the outcome of hearing aid provision.
Self-reports of hearing problems, sound aversiveness, and hearing aid expectations obtained before the fitting were found to be more closely related to the strength of certain personality traits than to audiometric hearing loss. Response bias also was associated with personality variables. Analyses of the collection of outcome measures produced a set of three components that were interpreted as a Device component, a Success component, and an Acceptance component. The Device component was construed as reflecting characteristics of the hearing aid whereas the two other components were construed as reflecting attributes of the wearer. The Success and Acceptance components were each significantly associated with several personality traits, but the Device component was not associated with personality. Variables available before the fitting accounted for 20 to 30% of each outcome component whereas amplification variables measured to verify the fitting accounted for only 10% on only one component.
As reported in previous research, personality is associated with self-report outcome data. However, if practitioners utilize existing measures of hearing problems at the prefitting stage, separate personality data will not yield additional leverage in prediction of long-term fitting outcomes. Traditional fitting verification data as measured in this study, proved minimally useful in prediction of long-term outcomes of the fitting. A large proportion of variance in self-report fitting outcomes has yet to be accounted for. Finally, it appears that certain types of questionnaires might be more appropriate for research evaluating new amplification devices, whereas a different questionnaire approach might be optimal for evaluating intervention effectiveness in a clinical context.