Perspectives on screening strategies for early detection of childhood hearing impairment

Abstract

The aims of this thesis were to assess the status of childhood hearing screening programmes, primarily in Europe, and to evaluate their performance against the parameters that make up a childhood hearing screening programme, such as test method, protocol, location, screening professional, and age of the infant at screening.

Studies I, III and III were ecological studies within the EUSCREEN project. The purpose of the EUSCREEN project was to develop a cost-effectiveness model and toolkit for implementation and modification of childhood hearing and vision screening programmes. Studies I, II and III made up an independent line of research that assessed existing childhood hearing screening programmes. A comprehensive questionnaire was delivered to professionals representing their local hearing screening programme. Questions included the provision, protocols, factors, and performance of newborn and childhood hearing screening. Study IV was a systematic review of literature. Studies were aggregated that compared referral or follow-up rate between parameters in a newborn hearing screening (NHS) programme. Study V investigated the presence of false negatives in the NHS programme in Region Stockholm. A retrospective analysis of the otoacoustic emission (OAE) results was performed among children with hearing impairment who had previously passed NHS.

Universal nationwide NHS existed in 25 of 30 high-income countries surveyed and 3 of 15 low- to middle-income countries. Universal preschool or school-entry screening existed in 17 out of 47 countries or regions. For NHS, countries that only used OAE for the test method had lower health spending compared to those that used automated auditory brainstem response (aABR). However, using aABR resulted in lower referral rates compared to OAE. Other factors that influenced referral rate were the number of rescreens, the age of the infant, the experience of the screening professional and the organization of the screening programme.

Out of the 12 programmes with a valid follow-up rate to diagnostic assessment, eight had rates below 90%. Factors such as personnel experience and knowledge and the location of follow-up can improve rates; however, few high-quality studies investigated this issue. There are other reasons why children with hearing impairment are not detected by NHS. Out of 1244 children with hearing impairment in study V, 24 were lost due to errors in documentation. Additionally, two OAE variables predicted hearing impairment among infants who previously met passing criteria (p<0.001). Increasing the stringency of passing criteria will increase the number of children with hearing impairment detected by screening.

The findings from this thesis may be used for implementing new programmes or improving existing ones. However, the results also suggest a significant deficiency in the process for monitoring and evaluation of hearing screening programmes. Out of 42 NHS programmes surveyed, 23 had valid referral rates and 12 had a valid follow-up rate. Out of 17 preschool or school-entry programmes, only two provided these data. Developing a process for collecting and reporting on existing outcomes is the necessary first step to quality improvement.