Hearing Sciences

CROSSSD Study: Development of a core outcome set for single-sided deafness (SSD) interventions



What is the study about and why is it important?

Single-sided deafness (SSD) refers to the condition where there is normal or near-normal hearing in one ear and a severe-to-profound hearing impairment in the other ear.

Good hearing in both ears is important for everyday listening tasks such as understanding speech in noisy environments, locating where sounds are, and identifying threats such as oncoming traffic.

Researchers have been assessing the benefits and harms (known as ‘outcomes’) of the available treatments for SSD inconsistently. Examples of outcomes that have been used include, how well an individual can hear speech above noise, how easily they can locate a sound, or how a device affects their quality of life. This makes it difficult to compare results between studies, making it harder to work out which treatment is best for the individual.

By involving healthcare users with experience in SSD treatments, audiologists, ENT surgeons, clinical researchers, and industry representatives; the CROSSSD study gathered international opinions via Delphi surveys and a web-based consensus meeting and found agreement on three measures that should always be reported on in SSD intervention studies. The core outcomes are (1) Spatial orientation, (2) Group conversations in noisy social situations, and (3) Impact on social situations.

If all future SSD intervention studies measure these core outcomes as a minimum, we can more easily compare results of different studies, improve research quality, and enhance clinical decision-making.

Further research is currently underway to help determine ‘how’ these core outcomes should best be measured.

Study update video

Study registration

COMET database entry

PROSPERO project entry

Contact us

Email the team


 Link to video on YouTube (to access captions). Video created by www.sciencesplained.com.


The CROSSSD study is supported by the NIHR Nottingham BRC.


Study management team

Roulla Katiri, PhD student
Derek J. Hoare, CROSSSD study supervision 
Kathryn Fackrell, CROSSSD study supervision
Pádraig T. Kitterick, expertise in severe-to-profound hearing loss
Deborah A. Hall, expertise in outcome measures

Patient and public involvement team

Adele Horobin, PPI manager
Nicholas Hogan, expertise in auditory implants for SSD
Nóra Buggy, expertise in hearing devices for SSD

International steering group

Iain A. Bruce, NIHR Manchester Biomedical Research Centre
Paul Van de Heyning, Antwerp University Hospital - University of Antwerp, Belgium
Jill B. Firszt, Washington University School of Medicine, USA

Peer reviewed publications

Katiri, R., Hall, D. A., Hoare, D. J., Fackrell, K., Horobin, A., Hogan, N., Buggy, N., Van De Heyning, P., Firszt, J. B., Bruce, I. A., & Kitterick, P. T. (2022). The Core Rehabilitation Outcome Set for Single-Sided Deafness (CROSSSD) study: International consensus on outcome measures for trials of interventions for adults with single-sided deafness. Trials. 23(1):764. doi: 10.1186/s13063-022-06702-1.

Katiri, R., Hall, D.A., Hoare, D.J., Fackrell, K., Horobin, A., Buggy, N., Hogan, N., & Kitterick, P.T. (2021). Redesigning a web-based stakeholder consensus meeting about core outcomes for clinical trials: Formative feedback study. JMIR Form Res. 5: e28878.

Katiri, R., Hall, D.A., Killan, C.F., Smith, S., Prayuenyong, P., & Kitterick, P.T. (2021). Systematic review of outcome domains and instruments used in designs of clinical trials for interventions that seek to restore bilateral and binaural hearing in adults with unilateral severe to profound sensorineural hearing loss ('single-sided deafness’). BMC Trials. 22: 220.

Katiri, R., Hall, D.A., Buggy, N., Hogan, N., Horobin, A., Van de Heyning, P., Firszt, J.B., Bruce, I.A., & Kitterick, P.T. (2020). Core Rehabilitation Outcome Set for Single Sided Deafness (CROSSSD) study: Protocol for an international consensus on outcome measures for single sided deafness interventions using a modified Delphi survey. Trials. 21: 238.

Hearing Sciences

Mental Health & Clinical Neuroscience
School of Medicine
University of Nottingham
Medical School, QMC
Nottingham, NG7 2UH

telephone: University Park +44 (0) 115 74 86900
Ropewalk House +44 (0) 115 82 32600
Glasgow +44 (0) 141 242 9665
email: hearing-research@nottingham.ac.uk