An audit of hearing aid quality in Denmark. II: Type of defects

In this investigation the type of defects in hearing aids (HAs) is described, and the stability of HAs is evaluated, based on prospective longitudinal data over an observation period of 2 years. An exchange of information between the Danish national hearing health service and hearing aid manufacturers, representing the private sector, demonstrates that overall external components to which the HA-user has access, are frequently defective. However, with time, internal components, to which the HA-user has no access, are frequently defective within the first year of use, whereas external components malfunction significantly more frequently after 3 years of use. Among the dispensed hearing aids, 11% were defective at the fitting, indicating insufficient quality control by the manufacturers. A prospective longitudinal investigation of 1141 defective HAs revealed that 12% of behind-the-ear HAs become defective within the first year of use, exhibiting the greatest stability. After 2 years of use, all in-the-canal HAs are defective, while only 33% of the in-the-ear HAs remain intact. It is concluded that the established exchange of information between the public and private sectors offers valid information on the quality of HAs; that the quality and stability of HAs is insufficient; and that the quality should be improved, (based on international criteria).