Toward a Model Clinical-Trials Protocol for Substantiating Hearing Aid User-Benefit Claims

Abstract

It has been argued that there is a need to adopt a uniform core set of dependent measures and test conditions for use in manufacturer-sponsored clinical trials to substantiate hearing device user-benefit claims in FDA applications. A framework for developing a model protocol was presented, and a core set of dependent measures and test conditions was suggested that may serve as a springboard for discussion. Given the state of the art, designing a protocol to evaluate hearing aid benefit requires that certain assumptions and compromises be made in defining this benefit and selecting test materials. The limitations of our knowledge and testing methods make it inevitable that the results of our efforts will not be perfect. The problems created by limited knowledge and methodology certainly are not unique to our discipline or to this endeavor. Although perfect prediction of everyday performance should be our goal, currently it cannot be our expectation. However, this should not deter us from our best attempt to reach our goal. The clinical-trials protocol described in this paper has been used in two manufacturer-sponsored clinical trials conducted at Walter Reed Army Medical Center. Although there has been general satisfaction with this protocol on the part of both the manufacturer and the researchers who have conducted these trials, the potential to improve this protocol certainly exists. The laboratory measures included in the Walter Reed protocol depend on traditional "objective" measures of speech recognition. There are other potentially useful methodologies (e.g., subjective ratings of intelligibility, paired-comparison techniques), and other dimensions of user performance (e.g., sound quality, loudness growth) that are ignored. Although the involvement of hearing researchers in manufacturer-sponsored clinical trials to substantiate user-benefit claims is relatively new, valuable experience has been gained in several clinical research laboratories. A collective effort on the part of manufacturers, researchers involved in this research activity, and government regulators, could lead to a model protocol that would benefit both hearing-impaired consumers and hearing instrument manufacturers.