Developing an International Core Outcome Set for SSD Interventions

Abstract

Unilateral hearing loss or single-sided deafness (SSD) is defined as normal or near-normal hearing in one ear and a severe-to-profound sensorineural hearing impairment in the other ear.1 Common causes of SSD in adulthood include vestibular schwannoma and associated surgery, Ménière's disease, and bacterial or viral infections. SSD affects an estimated 12 to 27 individuals in every 100,000 of the general population.2Shutterstock/Inspiring, hearing loss, deafness, technology.Figure 1: Steps to develop a core outcome set for SSD interventions for adults. Hearing loss, deafness, technology.Difficulties in daily life as a result of SSD vary considerably from person to person. Functional difficulties in everyday life are commonly reported, such as difficulties in speech perception in noisy environments and poor spatial awareness. SSD can also negatively affect one's psychological well-being, resulting in worries about losing one's hearing in the other ear and/or reduced confidence and belief in one's abilities to participate in social situations. Various social impacts of SSD can result from activity limitations and participation restrictions, including withdrawal from and within situations.3 The multidimensional burden of SSD on an individual's overall health is indicated by reductions in health-related quality of life.4 Interventions like a contralateral routing of signals (CROS) aid or a bone conduction device aim to alleviate the impact of SSD by rerouting signals from the impaired ear to the better-hearing ear.5 In the past decade, we have seen the introduction of cochlear implantation,6 which restores hearing by delivering information directly to the impaired side, thus creating a sensation of true binaural hearing. TREATMENT CHALLENGES The challenge faced by people diagnosed with SSD, health care professionals, and clinical researchers is understanding which intervention (if any) is ideal.7 How can we measure the benefits or harms associated with an intervention for SSD? Existing literature has highlighted inconsistencies in the benefits and risks (side effects), or outcome domains, assessed when evaluating these interventions. For example, clinical studies that evaluate these interventions have measured performances such as speech perception in quiet or noisy environments and sound localization. Studies have also assessed tinnitus symptom severity and quality of life. The tests (measurement instruments) that researchers have chosen to measure these effects also vary widely from study to study. For example, sound localization can be measured using a setup of four loudspeakers arranged at the front, back, and sides (90 degrees apart) or a more complex setup of six loudspeakers arranged in a semi-circle in front of the participant (30 degrees apart). This diversity of chosen measures poses a challenge to both health care users and professionals when comparing and contrasting various study outcomes. In some cases, researchers choose available measures because they are standardized or easily accessible, and not because of their importance to health care users or professionals themselves. ADDRESSING THE INCONSISTENCY Identifying appropriate outcome domains is crucial to designing clinical trials to evaluate the effects of various interventions for SSD.8 Selected outcomes need to be vital and tailored to key stakeholders such as health care users, professionals, or budget holders to minimize bias when making decisions about health care.9 Furthermore, the choice of outcome measures should be based on what is important and of interest to people making decisions about health care, not on what outcome instruments are available or most commonly used. The Core Outcome Measures in Effectiveness Trials (COMET) Initiative just celebrated its 10th anniversary. The network brings together researchers interested in the development of agreed and standardized sets of outcomes, known as core outcome sets. Part of the COMET work focuses on developing recommendations on minimum standards for the design of core outcome set (COS) studies.10 A COS is a recommendation of what should be measured and reported in all trials in a specific area as a minimum. If developed from the perspectives of all relevant stakeholders, a COS can overcome the problems imposed by the utilization of diverse measures. In the field of audiology and ENT, a group led by Professor Deborah A. Hall at the University of Nottingham has developed a COS for tinnitus.11 Professor Iain A. Bruce and his team at the NIHR Manchester Biomedical Research Centre are working on the PONCHO study: Prioritizing Outcomes iN Childhood Hearing lOss. THE CROSSSD STUDY The Core Rehabilitation Outcome Set for Single-Sided Deafness (CROSSSD) project is an international initiative that aims to develop a COS for SSD interventions. It aims to find an agreement on what outcomes are critical and should always be measured when evaluating interventions for SSD, using the methodology proposed by the COMET initiative. We have an advisory group of clinical professionals from the United Kingdom, United States, and Europe. The CROSSSD project also works closely with people who have lived experience of SSD. They have been integral to the design and delivery of the CROSSSD study. For example, a promotional video (http://bit.ly/2QbLJk) was developed alongside collaborators with lived experience of SSD to increase awareness of the project and help with global participant recruitment. Our methodology is as follows (Fig. 1): Systematic review of the published literature reporting interventions for SSD to identify the outcome domains and measurement instruments that have already been used.12 Workshops using a range of qualitative methods to explore patient perspectives on outcomes. Interactive online consensus exercise, known as a Delphi survey, with key stakeholders to identify which outcome domains are important when evaluating SSD interventions. Interactive consensus meeting with a subgroup of the key stakeholders to discuss the Delphi survey findings and recommend a minimum set of outcome domains that are relevant to all. So far, we have completed the systematic review of the literature. From 72 papers, we identified a total of 244 outcome domains. Many of these were duplicates or not directly relevant to SSD, and so we were able to produce a shortened list of 44 unique candidate outcome domains. The Delphi survey engaged 277 participants from 30 countries. They suggested five additional candidate outcome domains. The e-Delphi concluded in February 2020 and the CROSSSD team are currently preparing for the interactive consensus meeting to finalize the core outcome domain set. FUTURE STEPS Once a COS is developed, we would know what is important to measure in all studies; however researchers also need to consider how the included outcomes should be measured. The COSMIN (COnsensus-based Standards for the selection of health Measurement INstruments) international initiative has collaborated with the COMET initiative to develop guidelines for selecting outcome measurement instruments for outcomes included in a COS.13 For instance, if quality of life is an outcome in a COS, indicated to be critical and important to always measure for SSD interventions, COSMIN standards can help us establish what commonly agreed instrument or questionnaire everyone should utilize to measure it. Appropriate dis emination strategies14 will ensure that anyone designing a trial in this area will have a list of outcomes to measure as a minimum, alongside a list of recommended instruments to utilize. The COS will not prevent researchers from measuring additional outcomes or utilizing supplementary instruments. Future studies in the field should adopt the recommended COS to reduce the heterogeneity of measures utilized. Moreover, only outcomes meaningful to all stakeholders will be employed and, as a result, transparency will be established since both benefits and harms will be reported. Clinical researchers will be supported in thinking critically about what they are trying to measure, and they will not select their outcomes simply based on the popularity or accessibility of available instruments. Uptake of the COS will be encouraged internationally to improve research quality, enhance clinical decision-making, and facilitate meta-analysis in systematic reviews. Acknowledgements: The study sponsor is the University of Nottingham, United Kingdom. An independent review of the protocol has been conducted by Professor Paula R. Williamson at the University of Liverpool, as part of the Research Ethics Committee approval process. Ethical approval has been authorized by the Nottingham 2 Research Ethics Committee (IRAS Project ID: 239750), Health Research Authority (HRA), and Health and Care Research Wales (HCRW). Reference: 19/EM/0222. The CROSSSD study group acknowledges the support of the National Institute of Health Research Clinical Research Network (NIHR CRN) in participant recruitment. Dr. Deborah Hall is an NIHR senior investigator. The views expressed in this article are those of the author(s) and not necessarily those of the NHS, the NIHR, or the Department of Health and Social Care. To learn more, visit www.nottingham.ac.uk/go/CROSSSD or follow @CROSSSD_ on Twitter. Funding: The main body of work for this project is funded by the National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre (BRC), funding reference number BRC-1215-20003. Additional grants obtained: Graham Fraser Foundation Travel Grant to attend the 15th International Conference on Cochlear Implants and other Implantable Auditory Technology (Ci2018.org), where the study was first launched. Oticon Medical provided funding to purchase the DelphiManager software from the COMET Initiative, University of Liverpool. The funding bodies have no role in the study design and implementation, writing of this report, or decision to submit this report for publication.