The evidence-base for adult hearing aid fitting practices and implications for future provision

Student thesis: Phd

Abstract

Hearing loss is the third leading cause of years lived with disability. Its impact extends beyond communication difficulties and is associated with other conditions, including poor mental health and dementia. Hearing aids, which are effective devices for managing permanent hearing loss, are typically prescribed according to the individual's clinically obtained audiogram and verified using real-ear measurements (REM). However, the patient benefit of REM-guided hearing aid adjustments is unclear. In addition, in recent years, several remote self-administered hearing assessment tools have been developed, and individually prescribed adult hearing aid service delivery models have been proposed (e.g. self-fitting). Thus, evidence is needed to guide best practice. The overall aim of this PhD was to evaluate the outcomes of current and emerging practices in adult hearing aid service delivery and was addressed via three reviews, one randomised controlled trial and a protocol for a remote filtered speech test. Remote hearing assessment tools have been available for almost two decades; however, their functionality and accuracy have yet to be reviewed. The first pre-registered review in this PhD aimed to (i) synthesise and evaluate the functionality of remote self-administered hearing assessment tools (using the Mobile Application Rating Scale), (ii) determine if any of the identified tools have been evaluated in the literature, and (iii) report on the quality and accuracy of the published validation data (using Quality Assessment of Diagnostic Accuracy Studies-2). This review identified 187 remote hearing assessment tools and 101 diagnostic accuracy studies. Many tools, especially those using tones, had low functionality scores (e.g. poor engagement). Only 12% of the tools were evaluated, with wide variations in quality and performance characteristics. However, speech remote hearing assessment tools obtained the highest accuracy and quality scores, as they are less prone to calibration and background noise issues. The effectiveness of alternative delivery models that do not require hearing aids to be prescribed using the individual's audiogram is unclear. Thus, the second pre-registered review aimed to address this knowledge gap. The findings, although based on low-quality evidence from seven studies, revealed that custom-prescribed fitting, with REM verification, resulted in a variety of self-reported outcomes that were statistically superior to all delivery models except self-fitting based on daily adjustment, which resulted in sound quality and user preference superior to custom-prescribed fitting. REM use has been recommended since the 1990s, as it improves target matches compared to initial fits (i.e. without REM guidance); however, the clinical effectiveness of adjusting hearing aids guided by REM is unclear. Thus, the third and final pre-registered review aimed to synthesise evidence of benefit obtained by using REM. The findings, although based on low-quality evidence from six studies, revealed that REM led to statistically significant improvements in self-reported listening ability, speech intelligibility and listening preference. The importance of the benefit is unclear because: (i) minimal importance differences (MIDs; the smallest differences people, especially patients, say are important and could justify a change in management), and (ii) cost effectiveness have yet to be determined. Recent evidence, however, has shown an improvement in the accuracy of initial fittings and the review findings, based on older studies, may not be valid. Thus, it is unclear if REM is still needed in routine adult clinical practice. A pre-registered double-blind, randomised, mixed-methods clinical trial was performed to determine (i) if new hearing aid users preferred REM or initial fitting and (ii) the reasons for their preferences. Forty-five participants were fitted with both settings, each saved in a separate program. They were asked to pair
Date of Award1 Aug 2024
Original languageEnglish
Awarding Institution
  • The University of Manchester
SupervisorKevin Munro (Supervisor)

Keywords

  • Real-ear measurements
  • Prescriptions
  • Hearing aids
  • Remote hearing assessment

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