In 2005 the WHO estimated that globally 278 million people have a permanent hearing loss of more than 40 dB HL (WHO, 2006). Including milder losses of greater than 25 dB HL, this number increases to an estimated 642 million. The total number is expected to rise in the coming years. Hearing loss, usually assessed by psycho-acoustic measurements such as pure tone and speech audiometry, only provide a limited description of the consequences of hearing loss; there is ample evidence showing that hearing loss has significant negative effects on a person's health status more generally, varying from individual to individual and over time in a given individual. There is currently no single questionnaire in audiology that covers the broad perspective that the ICF represents nor a consensus on the most appropriate instrument that assesses the effects of hearing loss on the lives of adults as well as treatment outcomes. Initiated by the Nordic Audiological Society (NAS), the ICF Research Branch, the Classification, Terminology and Standards Team at WHO, the International Society for Physical and Rehabilitation Medicine (ISPRM), the International Federation of Hard of Hearing People, the International Society of Audiology, and the Swedish Institute for Disability Research (SIDR) teamed up to tackle this issue by developing the first version of the ICF Core Sets for hearing loss. The project was run under the leadership of SIDR and with the financial support of the Oticon Foundation.

The preparatory phase of the project included the following preparatory studies:

• A systematic literature review was performed to identify variables focusing on individuals with hearing loss, and to identify and re-classify the concepts addressed in measurement tools with the ICF as a reference. Two scientific paper have been published - one on the results of the review https://www.ncbi.nlm.nih.gov/pubmed/24313738 and one on the linking of instruments identified in the review to the ICF https://www.ncbi.nlm.nih.gov/pubmed/24329490
• A qualitative study (focus groups in the Netherlands and South Africa), aimed at identifying relevant aspects of functioning and contextual factors from the patient perspective was conducted. Additionally, individual interviews were performed in South Africa in order to account for cultural differences within the country. The publication can be found here: https://www.ncbi.nlm.nih.gov/pubmed/25311099
• A worldwide survey was conducted (https://www.ncbi.nlm.nih.gov/pubmed/24754459) to gather the opinion of international experts who have an expertise in hearing and hearing loss.
• To describe common problems experienced by individuals with hearing loss from a clinical perspective, data within a multicentre cross-sectional study have been collected from centres in South Africa, Brazil, China, Sweden and India. 

The results of these preparatory studies were presented at the international consensus conference, a multi-stage, iterative, decision-making and consensus process that took place from 4-6 May 2012 in Helsingør, Denmark. At this consensus conference, 21 hearing loss experts, including 4 persons with hearing loss, from 14 different countries worldwide and working in a broad range of professions (i.e.audiology, speech/ language pathology, rehabilitation sciences, audiological medicine, psychology, head and neck surgery, hearing device specialty/technical audiology) decided which ICF categories should be included in the first version of the ICF Core Sets for hearing loss.

117 ICF categories were selected for inclusion in the Comprehensive ICF Core for hearing loss. Based on the Comprehensive ICF Core Set, 27 ICF categories were selected for the Brief ICF Core for hearing loss. See the corresponding publication: https://www.ncbi.nlm.nih.gov/pubmed/24096864.

• Comprehensive ICF Core Set for hearing loss (download PDF)
• Brief ICF Core Set for hearing loss (download PDF)

The Brief ICF Core Set is in the process of being validated. Furthermore, steps toward developing a patient-reported outcome measure is currently underway.
For more information, feel free to contact Dr. Sarah Granberg sarah.granberg@oru.se, Audiological Research Centre, University Hospital in Örebro (Sweden), Örebro University