International Outcome Inventory for Hearing Aids: Data From a Large Swedish Quality Register Database

The purpose of this study was to analyze a database of completed International Outcome Inventory for Hearing Aids (IOI-HA) questionnaires obtained from over 100,000 clients fitted with new hearing aids in Sweden during the period of 2012-2016. Mean IOI-HA total scores were correlated with degree of hearing loss, unilateral versus bilateral fitting, first-time versus return clients, gender, and variation among dispensing clinics. The correlations with expectations, service quality, and technical functioning of the hearing aids were also analyzed.

Questionnaires containing the 7 IOI-HA items as well as questions concerning some additional issues were mailed to clients 3-6 months after fitting of new hearing aids. The questionnaires were returned to and analyzed by an independent research institute.

More than 100 dispensing clinics nationwide take part in this project. A response rate of 52.6% resulted in 106,631 data sets after excluding incomplete questionnaires. Forty-six percent of the responders were women, and 54% were men. The largest difference in mean score (0.66) was found for the IOI-HA item "use" between return clients and first-time users. Women reported significantly higher (better) scores for the item "impact on others" compared with men. The bilaterally fitted subgroup reported significantly higher scores for all 7 items compared with the unilaterally fitted subgroup. Experienced users produced higher scores on benefit and satisfaction items, whereas first-time users gave higher scores for residual problems. No correlation was found between mean IOI-HA total score and average hearing threshold level (pure-tone average [PTA]). Mean IOI-HA total scores were found to correlate significantly with perceived service quality of the dispensing center and with the technical functionality of the hearing aids.

When comparing mean IOI-HA total scores from different studies or between groups, differences with regard to hearing aid experience, gender, and unilateral versus bilateral fitting have to be considered. No correlation was found between mean IOI-HA total score and degree of hearing loss in terms of PTA. Thus, PTA is not a reliable predictor of benefit and satisfaction of hearing aid provision as represented by the IOI-HA items. Identification of a specific lower fence in PTA for hearing aid candidacy is therefore to be avoided. Large differences were found in mean IOI-HA total scores related to different dispensing centers.