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Commentary on the paper by Wake et al (see 238)
The field of audiological medicine has ridden the wave of technological advancement that has transformed many aspects of screening and intervention in medicine. We can screen newborns for hearing loss, however we are not sure what is the most cost effective and simple method. A screening test that can be referred to as the “golden standard”, still eludes us. With the incidence of permanent bilateral clinically significant hearing loss at just over 1 in 1000 births,1,2 the need for a simple, inexpensive, and reliable screening method is evident.
The importance of diagnosing hearing loss at an early stage led to screening originally of “at risk” groups in the form of a targeted screening programme. This approach has proved to be effective as over half of hearing impaired and deaf children can be identified. To identify the other half of hearing impaired children, universal newborn screening programmes are being used in countries including the UK. Various combinations of oto-acoustic emissions and auditory brain stem tests singly or in combination have been successfully tried. Early fitting of technically sophisticated hearing aids and surgical intervention by implantation of cochlear devices is being successfully practised in many centres and countries in both private and state health services.
The practice of both targeted and, more recently, of universal screening, has given us the capability to fit hearing aids very early in infancy. The availability of implanting cochlear devices surgically has also been available and has transformed the management of many cases. The fundamental question “Does this make a difference to the child’s development and life?” remains unanswered in many cases, as we still lack a scientific approach to predict the degree of success of early amplification and implantation at an early stage especially during infancy. There are many known variables to take into account, such as additional disabilities—visual impairment, cognitive impairment, genetic and specific learning disabilities. These all have an impact on the outcome of any intervention.
It has been claimed that early diagnosis of hearing impairment and appropriate habilitation leads to a better outcome as seen in improved language and speech development. This simple and logical concept has been propagated since the eminent work by Andreas Markides under the leadership of Professor Ian Taylor from Manchester, UK.3 It showed the beneficial effect of early diagnosis and habilitation of children with hearing impairment and deafness. A number of workers followed and reported similar results, but some of them lacked long term follow up and appeared to group together a number of factors influencing the outcome.
Effective management of hearing impairment is a multidisciplinary complex process where the outcome is dominated by a number of factors which may vary in their influential role for an individual child. One of the factors which has clearly been shown to be important in the outcome of a child’s habilitation is the degree of hearing impairment. Another widely held belief is that the age of diagnosis is an important determinant of outcome: the notion that the earlier hearing impairment can be identified, the earlier the child can be helped. The article published in this issue of Archives by Wake and colleagues4 claims to show that the age of diagnosis was not a relevant factor in dictating outcome as measured by speech and language assessment in this study carried out in Victoria State, Australia. Much like a googly from Shane Warne, this paper takes an unexpected turn away from conventional understanding and other reports in this field.3,5,6 The study comes to the conclusion that the degree of hearing impairment is the predominant factor influencing the outcome as assessed at the age of 7–8 years.
A weaknesses of this otherwise well constructed study is the small numbers of children, diagnosed early at 6 months of age, in the severe and profound hearing impaired groups. The mean age of diagnosis (1.8 years), hearing aid fitting (1.9 years), and early intervention programme (2 years) are all later than what would be possible following a universal newborn hearing screening programme. Another problem appears to be a lack of data on high frequency threshold of 4 kHz, which may have a crucial role in speech development.
Auro-oral communication and educational approaches to hearing impairment and deaf children has been significantly boosted by early diagnosis and amplification. This has been powered by the unproven notion and concept of a “critical period” of speech and language development related with audition. Wake et al challenge this concept and create debate about the relation of early diagnosis and outcome. Their study points to other known and unknown factors, highlighting the role of motivation and drive, personality, behaviour, auditory processing, and some other innate and unknown factors related with learning that have not been investigated in large follow up studies.
Some of these questions can only be answered by appropriately constructed, prospective, multicentre, large longitudinal studies. More research and auditing of various practices and processes are needed. Neither medical nor educational systems can work independently to answer these questions and a combined effort is needed. There is an ongoing need to concentrate on early diagnosis so that the habilitating processes can be applied and studied. The conclusion of the Wake et al study should not be seen as a case against the need for early diagnosis, but rather a challenge for universal screening. We need to conduct larger well constituted, prospective, multicentre studies to gather detailed information about all factors which may influence outcome. Then, and only then, can we practice evidence based audiology. Studies which highlight the need for further research and that challenge our conceptions are a potent weapon in our further understanding of child healthcare issues and our consequent management strategies.
Commentary on the paper by Wake et al (see 238)