Impact of Hearing Aid Service-delivery Model and Technology on Patient Outcomes: A Randomized Clinical Trial
Phase: NA
Conditions: Presbycusis
Sponsor: Yu-Hsiang Wu

 
 
Official Title of the study: Impact of Hearing Aid Service-delivery Model and Technology on Patient 
Outcomes: A Randomized Clinical Trial   
NCT number: NCT03579563  
Date of the document: 6/21/2024 
 
 

 
2 
Impact of hearing aid service-delivery model and  
technology on patient outcomes:  
A Randomized Clinical Trial 
 
Trial Protocol and Statistical Analysis Plan 
 
Version: Final 
Date: 6/21/2024 
 
 
 
 
 
 
 

 
3 
1 
ADMINISTRATIVE INFORMATION 
1.1 
Trial registration 
ClinicalTrials.gov Identifier: NCT03579563 
 
1.2 
Funding 
The study was funded by NIH/NIDCD R01DC015997. 
 
1.3 
Roles and responsibilities 
 
Name  
Contact information 
Affiliations 
Role and responsibilities 
Wu, Yu-
Hsiang  
yu-hsiang-wu@uiowa.edu  
Department of 
Communication Sciences 
and Disorders, The 
University of Iowa 
Principal investigator: funding 
acquisition, study design 
conceptualization, project 
supervision, report writing  
Ricketts, 
Todd  
todd.a.ricketts@vumc.org  
Department of Hearing 
& Speech Sciences, 
Vanderbilt University 
Medical Center 
Principal investigator: funding 
acquisition, study design 
conceptualization, project 
supervision, report writing  
Oleson, 
Jacob  
jacob-oleson@uiowa.edu  
Department of 
Biostatistics, The 
University of Iowa 
Biostatistician: data processing, 
data analysis, report writing 
Stangl, 
Elizabath  
elizabeth-stangl@uiowa.edu  
Department of 
Communication Sciences 
and Disorders, The 
University of Iowa 
Audiologist: hearing aid fitting, 
data collection, data curation, 
report writing 
Branscome, 
Kjersten  
kjersten.branscome@vumc.org  Department of Hearing 
& Speech Sciences, 
Vanderbilt University 
Medical Center 
Audiologist: hearing aid fitting, 
data collection, data curation 
 
2 
INTRODUCTION 
2.1 
Background and rationale 
Age-related hearing loss presents a significant national challenge due to its high prevalence and 
significant quality-of-life consequences. Although hearing aids (HAs) are the primary choice for 
managing age-related hearing loss, their adoption rate remains low. One commonly reported reason 
for not adopting HAs is the financial and physical barriers associated with traditional hearing 
healthcare, which involves multiple visits to licensed professionals (such as audiologists) for 
diagnosis and a lengthy process of fitting and fine-tuning prescription HAs. This traditional service-
delivery model is referred to as the AUD service model.  
 
The high cost of HA devices further exacerbates the accessibility and affordability challenges of 
traditional hearing healthcare. Specifically, a variety of technologies and features have been 
implemented in modern HAs, including multi-channel wide dynamic range compression, directional 
microphones, noise reduction algorithms, and wireless functionality. These technologies have 
evolved from basic algorithms into more sophisticated and complex designs. However, these high-
end technologies and features often make HAs more expensive and less affordable.  
 
In recent years, over-the-counter (OTC) HAs have emerged as an alternative to address some of the 
affordability and accessibility issues of the AUD service. This direct-to-consumer model enables 
users to self-determine hearing loss, self-fit HAs, and self-manage the device without the need for 

 
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professional support. This direct-to-consumer model is referred to as the OTC service model. 
Additionally, it has been advocated that a hybrid service model, where professionals fit OTC HAs 
(referred to as the OTC+ service model), could offer affordable and quality amplification 
interventions.  
 
Previous clinical trials have shown that the OTC service model yields outcomes comparable to the 
AUD service model. Furthermore, prior research has found no statistically significant or clinically 
important differences in patient outcomes between high-end and low-end HAs. However, no prior 
research has systematically examined the effectiveness of HA fitting service models and HA 
technology levels in the same study. Additionally, no prior research has investigated the patient 
outcomes of the OTC+ service model.  
 
2.2 
Objective 
To determine the effect of HA fitting services (AUD, OTC+, and OTC) and technology levels (high-
end and low-end) on patient outcomes. 
 
2.3 
Trial design 
This is a two-site randomized controlled trial. Participants will be randomly assigned to one of six 
parallel arms, which are factorial combinations of three service models (AUD, OTC+, and OTC) and 
two HA technology levels (high-end and low-end). Baseline measures will be administered before 
HA fitting and patient outcomes will be assessed six to seven weeks post-HA fitting.  
 
3 
METHODS: PARTICIPANTS, INTERVENTIONS, AND OUTCOMES 
3.1 
Study site 
The study will be conducted in the Hearing Aid and Aging Research Laboratory, Department of 
Communication Sciences and Disorders, the University of Iowa and the Dan Maddox Hearing Aid 
Research Laboratory, Department of Hearing & Speech Sciences, the Vanderbilt University Medical 
Center. The two sites, one in Iowa City (a more rural locale) and the other in Nashville (a more urban 
locale), provide us with the opportunity to engage a diverse range of participants. 
 
3.2 
Eligibility criteria 
3.2.1 Inclusion criteria: 
• 
Adults between 55 and 85 years old 
• 
Adult-onset, bilateral, mild-to-moderate sensorineural hearing loss 
o Pure-tone average across 500, 1000, 2000, and 4000 Hz between 25 and 55 dB HL  
o Thresholds from 500-4000 Hz no poorer than 65 dB HL, with up to 2 thresholds 
outside this criterion by < 10 dB still being eligible. 
• 
No prior HA experience 
 
3.2.2 Exclusion criteria: 
• 
Non-native speaker of English  
 
3.3 
Arms 
• AUD/High-end: In this group, audiologists will fit bilateral high-end prescription HAs 
according to the best practice guidelines. 
• OTC+/High-end: In this group, audiologists will provide brief services to fit bilateral preset-
based OTC-HAs, which are simulated using high-end prescription HAs. 

 
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• OTC/High-end: In this group, a pair of preset-based OTC HAs, simulated using high-end 
prescription HAs, will be provided to each subject. Participants will take the full initiative and 
responsibility for learning and using the HAs without assistance from audiologists. 
• AUD/Low-end: In this group, audiologists will fit bilateral low-end prescription HAs 
according to the best practice guidelines. 
• OTC+/Low-end: In this group, audiologists will provide brief services to fit bilateral preset-
based OTC-HAs, which are simulated using low-end prescription HAs. 
• OTC/Low-end: In this group, a pair of preset-based OTC HAs, simulated using low-end 
prescription HAs, will be provided to each subject. Participants will take the full initiative and 
responsibility for learning and using the HAs without assistance from audiologists. 
 
3.3.1 Interventions: HA fitting services 
The services will be provided by audiologists in the Hearing Aid and Aging Research Laboratory, 
Department of Communication Sciences and Disorders, the University of Iowa and the Dan Maddox 
Hearing Aid Research Laboratory, Department of Hearing & Speech Sciences, the Vanderbilt 
University Medical Center. 
 
3.3.1.1 AUD service model  
In this service model, audiologists will fit prescription HAs according to the best practice guidelines. 
The fitting protocol will include the following measures: pure-tone audiometry to determine hearing 
threshold, the Client Oriented Scale of Improvement questionnaire (COSI)1 to evaluate individual 
listening needs, measurement of loudness discomfort levels (LDL)2,3 to determine sound levels that 
are uncomfortably loud, and the QuickSIN4 to assess unaided speech recognition performance in 
noise. Audiologists will configure the HAs and select the appropriate slim tube length, ear dome size, 
and type for each participant based on assessment results, NAL-NL2 prescriptions,5 and their clinical 
experiences. Audiologists will then conduct probe-microphone real-ear measures to verify the gains 
of the HAs, and make further adjustments based on participant’s feedback for comfort and sound 
quality. Additional hearing aid memories will be added and features will be adjusted based on the 
participants’ listening needs. Audiologists will also provide orientation (e.g., insertion, removal, and 
care of devices, smartphone app installation and orientation) and counseling (e.g., establishing 
realistic expectations of amplification) services. Participants will have the flexibility to schedule 
follow-up appointments with audiologists as often as needed.  
 
3.3.1.2 OTC+ service model  
In this service model, audiologists will provide services to fit preset-based OTC HAs. These services 
include conducting pure-tone audiometry to determine hearing thresholds and selecting the 
appropriate preset (from the four available presets, detailed below), slim tube length, ear dome size, 
and type. Selections will be based on the participant’s audiogram, NAL-NL2 targets, and the 
audiologist’s clinical experience. Audiologists can use the volume control and smartphone apps to 
make adjustments to the HAs as needed, but they will not use HA fitting software to program the 
devices as prescription HAs. Audiologists will also provide brief HA orientation and counseling. All 
services, except for pure-tone audiometry, will be completed in a 30-minute session. Participants will 
be allowed up to two follow-up visits of 15 minutes each for additional instruction or to address 
issues with the devices. 
 
3.3.1.3 OTC service model 
In this service model, participants will self-fit preset-based OTC HAs. To self-select the OTC HA’s 
preset, participants will use a Hearing Aid Selector kiosk app installed on a tablet computer to listen 

 
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to sounds recorded from each preset. The selection process will be conducted without assistance from 
audiologists. After selecting the preferred preset for each ear, participants will receive a package 
containing a pair of OTC HAs, which are simulated using prescription HAs (detailed below), and 
accessories including domes, slim tubes, and cleaning tools. The HAs will come with medium-length 
slim tubes and medium-sized dome tips of the style defaulted to the selected preset. The package will 
also include slim tubes of different lengths and various dome types in different sizes for replacement. 
During the trial period, participants will be permitted to return to the laboratory to reselect presets or 
request HA replacements if they encounter device-related issues they cannot resolve. 
 
3.3.2 Interventions: Hearing aids  
Two commercially available behind-the-ear prescription HA models will be used: a high-end model 
(retail price per pair ≈ $4,400 at the commencement of the study in 2018) and a low-end model (retail 
price per pair ≈ $1,100). Both models are from the same manufacturer but have different chipsets. 
HAs are coupled to the user’s ears using slim tubes and non-custom dome tips, Participants will not 
be able to recognize the HA model based on the device case or the smartphone apps. The contrasts 
between high-end and low-end HAs are shown in the table below. 
 
Feature 
High-end HA 
Low-end HA 
Signal processing channels 
48 
12 
Hearing programs 
6 
4 
Extended dynamic range 
Yes 
No 
Extended bandwidth 
Yes 
No 
Directionality 
Automatic/Adaptive 
Automatic/Fixed 
Narrow directionality  
Yes 
No 
General-purpose noise reduction 
Yes 
Yes 
Impulse noise reduction 
Yes 
No 
Spatial noise reduction 
Yes 
No 
Reverberation reduction 
Yes 
No 
Wind noise reduction 
Yes 
No 
Feedback cancellation  
Yes 
Yes 
Smartphone app 
Yes 
Yes 
Volume control 
Yes 
Yes 
Program control 
Yes 
Yes 
Gain-frequency response 
adjustment  
Yes 
No 
Directionality control (direction 
and width of the beam) 
Yes 
No 
 
3.3.2.1 OTC HAs simulation 
OTC HAs will be simulated using prescription HAs. OTC HAs will use a validated preset-based 
fitting method developed from audiometric data sourced from the National Health and Nutrition 
Examination Survey (NHANES).6,7 Four presets (i.e., four pre-determined gain-frequency responses) 
are available for selection. It is estimated that these four presets are appropriate for 67.9% of the 
NHANES older adults with mild-to-moderate hearing loss. Both high-end and low-end HAs will be 
used to simulate OTC HAs. 
 

 
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3.3.3 Materials used in interventions 
All participants will be encouraged to use the user manual, quick start guide, and simulated HA 
dispenser websites created for the trial to learn about the devices. These websites offer information 
about hearing loss, as well as the specifications, use, care, and troubleshooting of HAs through text 
and videos. They also include a frequently asked questions page. These print materials and websites 
mimic the information provided by typical dispenser websites but use fabricated manufacturer and 
product names. The simulated websites for the high-end and low-end HAs are 
https://www.precisehearingcare.com/ and https://www.exacthearingcare.com/, respectively. 
 
3.4 
Outcomes 
3.4.1 Primary outcomes 
3.4.1.1 In-situ Glasgow Hearing Aid Benefit Profile: HA use (EMA-GHABP-Use) 
The GHABP8 is a questionnaire that measures HA users’ listening experience in four situations: TV 
listening, small conversation in quiet, conversation in noise, and group conversation. The GHABP 
will be administered using smartphone-based Ecological Momentary Assessment (EMA) to collect 
in-situ self-reports. The GHABP items evaluate HA use averaged across the four listening situations 
form the EMA-GHABP-Use score. The score ranges from 1 (not use HA at all) to 5 (use HA all the 
time). The EMA-GHABP-Use will be measured between 6- and 7-weeks post-intervention for one 
week. 
 
3.4.1.2 In-situ Glasgow Hearing Aid Benefit Profile: Global score (EMA-GHABP-Global) 
The EMA-GHABP-Global score is derived from the items of the in-situ GHABP that evaluate a 
patient’s hearing disability, hearing handicap, HA benefit, and HA satisfaction across the four 
listening situations. This score ranges from 1 (poorer outcome) to 5 (better outcome). It will be 
measured for one week both pre-intervention and between 6 and 7 weeks post-intervention. During 
the pre-intervention assessment, only the items related to hearing disability and hearing handicap will 
be used.  
 
3.4.2 Secondary outcomes 
3.4.2.1 Retrospective Glasgow Hearing Aid Benefit Profile: HA use (Retro-GHABP-Use) 
The GHABP will also be administered as a retrospective questionnaire. The items evaluate patient’s 
HA use averaged across the four listening situations derive the Retro-GHABP-Use score. The score 
ranges from 1 (not use HA at all) to 5 (use HA all the time). The Retro-GHABP-Use will be 
measured at 6-week post intervention. 
 
3.4.2.2 Retrospective Glasgow Hearing Aid Benefit Profile: Global score (Retro-GHABP-Global) 
The Retro-GHABP-Global score is derived from the items of the retrospective GHABP that evaluate 
a patient’s hearing disability, hearing handicap, HA benefit, and HA satisfaction across the four 
listening situations. The score ranges from 1 (poorer outcome) to 5 (better outcome). The Retro-
GHABP-Global will be measured pre-intervention and at 6 weeks post-intervention. In the pre-
intervention assessment, only the items related to hearing disability and hearing handicap will be 
used. 
 
3.4.2.3 Profile of Hearing Aid Performance (PHAP) 
The PHAP9 is a questionnaire designed to measure the performance of HAs across various listening 
situations in seven domains. The scores of the five domains related to speech communication will be 
averaged to derive the PHAP score. The score ranges from 1 (good performance) to 99 (poor 
performance). Participants will complete this questionnaire pre-intervention and at 7 weeks post-
intervention. The difference between pre- and post-intervention scores (benefit score; referred to as 

 
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PHAP-Benefit) will be used in the analysis. PHAP-Benefit ranges from -99 (intervention is 
detrimental) to 99 (intervention is beneficial). 
 
3.4.2.4 Hearing Handicap Inventory for the Elderly (HHIE) or Hearing Handicap Inventory for 
Adults (HHIA) 
The HHIE10 and HHIA11 are questionnaires designed to measure participant’s perceived hearing 
handicap. For participants aged 65 and over and younger than 65 years old,, the HHIE and HHIA will 
be used, respectively. The score ranges from 0 (no handicap) to 100 (more handicap). Participants 
will complete this questionnaire pre-intervention and at 7 weeks post-intervention. The difference 
between pre- and post-intervention scores (benefit score; referred to as HHIE/A-Benefit) will be used 
in the analysis. HHIE/A-Benefit ranges from -100 (intervention is detrimental) to 100 (intervention is 
beneficial). 
 
3.4.2.5 Satisfaction With Amplification in Daily Life (SADL)  
The SADL12 is a questionnaire designed to measures participant’s perceived HA satisfaction. The 
score ranges from 1 (low satisfaction) to 7 (high satisfaction). Participants will complete this 
questionnaire at 7 weeks post-intervention. 
 
3.4.2.6 Connected Speech Test (CST)  
The CST13 is a speech recognition test designed to simulate daily speech communication. The CST 
will be administered in a sound-treated booth. Speech and noise will be presented at 0 and 180 
degrees azimuth at a +3 dB signal-to-noise ratio (speech = 65 dBA). The score ranges from 0 
(understand no speech) to 100 (understand all speech). Participants will complete this test pre-
intervention and at 6 weeks post-intervention. The difference between pre- and post-intervention 
scores (benefit score; referred to as CST-Benefit) will be used in the analysis. CST-Benefit ranges 
from --100 (intervention is detrimental) to 100 (intervention is beneficial). 
 
3.5 
Sample size 
The trial is designed to detect a 0.3-point difference in the primary outcome GHABP. This difference 
is considered a minimal important change (MIC), as participants would prefer one HA intervention 
over another if they had the opportunity to try both.14 Power calculations are conducted for post-hoc 
comparisons of the main effects, specifically the pairwise comparisons between AUD, OTC+, and 
OTC. Based on the MIC and an estimated standard deviation from prior research (0.53 points), a 
two-sample t-test would achieve 88% power to detect a difference of 0.3 points, using a conservative 
Bonferroni adjustment to the alpha level of 0.0167 (0.05/3), assuming 40 participants in each of the 
six arms, totaling 80 participants in each service model for the pairwise comparisons. Therefore, a 
total of 240 participants will complete the trial, with 120 participants in each study site. 
 
3.6 
Allocation 
The treatment allocation sequence is generated using computer-generated random numbers. The 
assignment of treatment is based on the order of being eligible to participate in the study.  
 
3.7 
Blinding 
Participants will be kept blind to the HA technology level. However, blinding participants to the 
services they receive is not feasible. Therefore, the study will employ a form of deception where 
participants will be informed that the trial has only one treatment arm and will be provided 
information solely on the services they receive. The research assistants responsible for collecting 
outcome data will remain blinded to the treatment assignment. 
 

 
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3.8 
Participant timeline 
Participants for this clinical trial will be recruited through print, radio, and online advertisements, as 
well as mass emails/letters to established registries/lists. The principal investigators of the trial will 
obtain consent from participants. Following enrollment, audiologists who are blinded to the treatment 
assignment will administer pre-intervention assessments. Participants will then start the one-week 
EMA-GHABP pre-intervention measure. Seven days later, 
participants will return to the laboratory where audiologists, 
now informed of the treatment assignment, will administer the 
interventions. A 6-week trial will then follow. At the end of the 
trial, participants will return to the laboratory where research 
assistants, who are blinded to the treatment assignment, will 
administer outcome measures. Participants will then start the 
one-week EMA-GHABP post-intervention measure. Seven 
days later, participants will return to the laboratory to complete 
the remaining outcome measures. Participants will be 
debriefed and compensated for their participation. Refer to 
Figure 1 for the participant timeline. 
 
3.9 
Adverse events  
Adverse events will be monitored for each subject during their 
participation in the study, which average 8 weeks from the 
time the participants entered the study. 
 
4 
STATISTICAL ANALYSIS PLAN 
Analyses will be conducted to determine the effect of service 
model, technology level, and their interaction on outcomes. For 
the primary outcomes, EMA-GHABP-Use and EMA-GHABP-Global, linear mixed models (LMM) 
will be used. LMM is selected because the primary outcomes will be collected using the EMA 
methodology and therefore consists of repeated observations within each participant. Linear 
regression models will be used for the secondary outcome dependent variables, including Retro-
GHABP-Use, Retro-GHABP-Global, PHAP-Benefit, HHIE/A-Benefit, SADL, and CST-Benefit 
scores. 
 
For all analyses, study site (Iowa and Tennessee) will be controlled for in the model. For both EMA-
GHABP-Global and Retro-GHABP-Global, the pre-intervention GHABP scores will be controlled 
for in the model, with the repeated observations of pre-intervention EMA-GHABP-Global being 
averaged within each participant before being controlled for in the LMM. Pairwise comparisons (e.g., 
AUD vs. OTC+) will be conducted with an alpha level adjustment using the Tukey method. Two-
tailed tests will be employed, with a significance level of .05. All statistical analyses will be 
performed using R statistical software. 
 
4.1 
Missing data 
There will likely be participants who cannot be reached during the follow-up or decide to withdraw 
from the study. We plan to conduct both per-protocol (PP) analysis on participants who completed 
the study and intention-to-treat (ITT) analysis on all enrolled participants. The ITT analysis will be 
conducted only for the primary outcome, EMA-GHABP-Use, which represents HA use. For those 
who withdraw from the study, their EMA-GHABP-Use scores will be set to 0, indicating they would 
not use HAs if the outcome measures had been administered. 
 
OTC+/High-end 
Subject recruitment / screening 
Pre-intervention assessment 
Randomization 
OTC+/Low-end 
OTC/Low-end 
OTC/High-end 
AUD/High-end 
AUD/Low-end 
6-week to 7-week post-intervention 
assessment 
Figure 1. Participant timeline 

 
10 
 
 
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