Cochlear Implant Referrals in Adults With Severe-to-Profound Hearing Loss in the United Kingdom (CIRCA-2): Protocol for a Repeat National Multicenter Retrospective Observational Study.

Background: Cochlear implantation (CI) is a highly effective intervention for adults with severe-to-profound hearing loss, yet uptake across the United Kingdom remains low despite clear National Institute for Health and Care Excellence (NICE 2019) guidance and well-established clinical benefits. The original Cochlear Implant Referral Criteria Audit (CIRCA-1) identified marked inequities in access to CIs in 2022, with lower referral rates among older adults, males, and individuals from socioeconomically deprived areas, alongside individuals from minority ethnic backgrounds being less likely to be informed of their eligibility for referral. Since then, national awareness initiatives and the expansion of the existing local "CI Champions" scheme have aimed to address these inequities, improve awareness of CI candidacy, and improve the quality of discussions with patients about options for CI referral. This repeat assessment aims to assess the success of these interventions to identify improvements in access to CIs as well as persisting barriers. Objective: CIRCA-2 is a national, multicenter, retrospective observational audit designed to re-evaluate adult CI referral pathways and measure progress since the first audit cycle. Methods: The study will include adults assessed in secondary-care ear, nose, throat, and audiology departments between July and December 2025 whose audiometric thresholds meet NICE TA566 criteria. Participating centers will identify eligible patients using the British Cochlear Implant Group Crystal Report within Auditbase, and anonymized demographic, audiometric, and service-level data will be extracted. The primary outcomes are the proportions of patients meeting NICE TA566 criteria who were informed of their eligibility and referred for CI assessment, with comparisons made to CIRCA-1 data. Secondary analyses will examine adherence to national standards and predictors of discussion and referral using multivariable modeling. In addition, the study will assess the number of patients within criteria for the Comparing Cochlear Implants With Hearing Aids in Adults (COACH) trial and those meeting CI criteria in one ear only. Results: Retrospective data for the period July 1 to December 31, 2025, were collected between January and March 2026. Eighty-three sites submitted data relating to 15,060 patients. Data analysis is projected to be complete by October 2026, with publication of final results expected in early 2027. Conclusions: By quantifying change over time, CIRCA-2 will provide an updated national picture of CI referral practice, highlight any persisting barriers, and inform future strategies to promote equitable access to CIs.