Application of quality standards to hearing aid services

BMJ 1994;308:1454 (4 June)

Editorials

Application of quality standards to hearing aid services

Recent years have seen a welcome increase in emphasis on robustoutcome measures to assess the effectiveness of interventionin clinical practice. For diseases that are severe or life threateningthe outcomes can be relatively simple and robust (for example,survival rates). For conditions resulting in chronic disability,however, deriving outcomes to assess quality standards is harder.Because of spidemiological evidence that hearing diability inadults is common- and fewer than one third of candidates forhearing aids have one- attention is now turning to the effectivenessof hearing aid services for adults and the assessment of thequality of the devices provided.

Sounds Like Quality, guidelines produced by the National Committeeof Profession in Audiology, suggests sensible targets for thedelivery of hearing aids and rehabilitation to people with impairedhearing. Notably lacking, however, are recommendations for assessingoutcome, either in terms of the ability of hearing aids to improvethe understanding of speech or in terms of the extent to whichthe hearing aids and rehabilitation alleviate the diabilitiessuffered by hearing impaired people.

Discussing the assessment of the hearing aids, Lyregaard hasadvanced two main arguments. Firstly, he says that the traditionalelectroacoustic specifications for the performance of hearingaids inadequately describe the aids' performance in everydaylife, expecially give the added complexity of modern techniquesof signal processing. Secondly, he says that the rational applicationof new technology will require clinical trials that incorporatemeasures that are based on listeners' needs rather than laboratorymeasurements. Current knowledge indicates that, as well as measuresof performance (such as the discrimination of speech), subjective(self reported) measures of hearing disability are needed. Althoughsubstantial advances have been made, suitable outcome measuresto assess the overall and differential health gain are not yetavailable. Evaluation of the efficacy of current services andnational decisions about future changes are impossible withoutthem. Such measures need to be tailored for use in several circumstances:routine practice as part of ongoing audit; large scale studiesof change in the NHS hearing aid services; and evaluation ofnew technologies. These may seem daunting requirements, yetaudiology has a much better track record in developing outcomemeasures than many other disciplines concerned with disability.