Sunday, 6 March 2011

Where commercial and clinical interests collide: the case of auditory processing disorder

I’m currently writing a blogpost for the Wellcome Trust focusing on my research on auditory processing problems in children with language difficulties. While checking out links I realised there was another post I wanted to write on this topic: not on the science, but on the politics.

As I’ll explain more in the Wellcome Trust piece, auditory processing disorder (APD) is a diagnosis that is made when a child obtains a normal audiogram, i.e. demonstrates normal ability to detect sounds, yet appears not to perceive sounds normally. A common complaint is difficulty hearing speech in noise. Various experimental tests of auditory processing may show the child doesn’t appear to discriminate differences between sounds that vary in features such as pitch, duration or modulation (wobble).

APD is unusual in that there are no agreed diagnostic tests. I was pretty certain APD didn’t feature in the diagnostic bible of the American Psychiatric Association, the DSM-IV, and googling around suggests it’s not going to feature in the new DSM-5 either.   I was surprised, though, to find a mention of APD, or something very like it, in the alternative bible, the International Classification of Diseases. My searches turned up the category of “Abnormal auditory perception unspecified”, code 388.40 in ICD-9-CM. An accompanying statement on the website read: "388.40 is a billable ICD-9-CM medical code that can be used to specify a diagnosis on a reimbursement claim”. 

Given the lack of agreement on diagnostic criteria and lack of recognition in formal guidelines, it’s impossible to find sensible epidemiological data on APD. My impression, though, is that it’s a diagnosis that is quite commonly made in the USA and Australia but is much less so in the UK. A few years ago, I attended a small UK conference organised by the British Society of Audiology on APD. Many of those attending were audiologists working in the National Health Service (NHS). They wanted to update their knowledge and skills, but were apprehensive of this category, which for many of them was a new one. They were particularly concerned that scarce NHS resources might be diverted to diagnosing a condition of uncertain validity, and even more concerned at the lack of any agreed methods for treating it. The conference organisers had done their best to include a session on intervention, and had written to various American experts who were known to have developed specific approaches to APD. They did not have much joy, however. One expert explained that she didn’t give talks about her intervention, but if the organisers liked, she could run a course on it. I’d never come across this kind of thing before: for the other neurodevelopmental disorders I work on, people who have expertise in intervention will talk to other professionals about what they are doing, and be willing to present information on its rationale, methods and efficacy. Not the case here. This was closed information for which one paid money. And since there was also no published information on rationale, methods and efficacy, it was very much a case of taking it on trust. No thanks, said the organisers.

Are people in North America just less sceptical than those in the UK? The answer is no. While hunting for a mention of APD in DSM, I found a clinical policy bulletin by Aetna.They wrote a critical account of APD and its treatment, and I was pleased to see they cited a recent review by Dawes and Bishop (2009). Their overview stated: “Aetna considers any diagnostic tests or treatments for the management of auditory processing disorder (APD) (previously known as central auditory processing disorder (CAPD)) experimental and investigational because there is insufficient scientific evidence to support the validity of any diagnostic tests and the effectiveness of any treatment for APD.” Further googling revealed that Aetna is a US medical insurance company.

Putting it all together, one can’t avoid the conclusion that APD is Big Business. Not in the UK, where most of our audiologists are working for the hard-pressed National Health Service, and have no motivation to diagnose this condition. In the USA and Australia, however, audiologists in private practice have considerable incentive to diagnose APD, as they can then offer expensive treatments for it. The ICD-9-CM code opens the door to allow people to claim these expenses on medical insurance. I initially found it strange that by far the most objective and thorough analysis of APD I could find was found on the website of an insurance company, but then realised they are the ones who have an interest in being sceptical about this diagnostic category.

The sad thing about all this is that caught in the cross-fire are children whose specific difficulties may have an auditory basis. Yet none of the clinicians seems motivated to develop robust diagnostic tools, and interventions are dreamt up without adequate scientific basis or evaluation. This is a downside of a privatised healthcare system: practitioners benefit from making diagnoses but not from testing their validity.


  1. APD isn't something I know a huge deal about. But from conversations with colleagues in the UK, it seems as though another worry is that, if a child sees an audiologist and is diagnosed with APD, they may not then have access to other specialists. For example, a child with language impairment may miss out on speech and language therapy because they've already been diagnosed with APD. Is there any truth in this?

  2. Hi Jon! Yes, that can happen. There does seem to be less multidisciplinary working between audiologists and other professions in the UK: one of the things we recommended in the Dawes/Bishop review was better integration of assessments between audiologists with speech-language therapists and psychologists. It cuts both ways: children with complex problems need good audiological assessments too. Problem is the tests available to audiologists for diagnosis of APD often have linguistic content and so confound language impairment with auditory problems. Dave Moore at MRC Institute of Hearing Research in Nottingham has been developing nonverbal tests of auditory processing, but it's unclear if they'll confirm APD as a coherent disorder :

  3. Tiana Leonard7 March 2011 17:59

    Hi Dorothy. Once again, you've raised a really important issue. Your post reminded me of one of my many grant rejections. Because of the prevalence of the diagnosis of "auditory processing disorder", my colleague, Linda Lombardino and I submitted a grant to study the characteristics of children who had received the diagnosis. We spent lots of time discussing the fact that there were no objective criteria, and suggested a battery of auditory and language tests that might be helpful in characterizing children who received the diagnosis. The grant was turned down, because there were no objective criteria! Which, of course, was the whole point of our grant. We thought we had explained that we were using the term in an objective way to describe children who had received the diagnosis. The purpose of the grant was to determine if there were any diagnostic tests or brain anomalies that characterized these children or whether their problems could all be subsumed under existing diagnoses (including "worried well"). I've always been sorry that we didn't try harder to pursue the project. It's terrible that parents are made to feel that their children have something defined that they should be spending money to treat when there is absolutely no supportive evidence.

  4. Charlie Wilson (@crewilson)7 March 2011 18:57

    I find the process of reification of new disorders fascinating, particularly the questions of the initial impetus and of cases that don't quite make the criteria for a specific diagnosis. Ben Goldacre pushes the idea that nowadays this can be drug company driven (e.g. social anxiety disorder & female sexual dysfunction). Obviously this is a different case, but the idea of profit pops up again. I'd be fascinated to know whether you think this process (giving it a name, fixing diagnostic criteria) is always overall a good thing for a condition. And particularly in developmental disorders, where perhaps criterial diagnosis is harder??

    But I wondered: surely the more widespread, validated, and accepted a diagnosis is, the bigger the market for people with untested treatments? So I wonder whether, in fact, there is a profit motive for validation.

    Also, does having a really well validated diagnosis with research-derived criteria actually stop people from offering expensive and unproven treatments with wildly exaggerated claims attached to them?

  5. Thanks for comments, Tiana and Charlie.
    Tiana: I’d be very surprised if you would have found anything consistent in these children. My grad student Piers Dawes attempted to characterise them and found a very heterogeneous group, including a subset who appeared to have features of autism spectrum disorder, ADHD or dyslexia.
    Dawes, P., & Bishop, D. (2010). Psychometric profile of children with auditory processing disorder (APD) and children with dyslexia. Archives of Disease in Childhood, 95, 432-436.
    Dawes, P., Bishop, D. V. M., Sirimanna, T., & Bamiou, D. E. (2008). Profile and aetiology of children diagnosed with auditory processing disorder (APD). Journal of Pediatric Otorhinolargyngology, 72, 483-489.
    Charlie: a very good question. I’m fascinated by the whole question of how we use labels for children with developmental disabilities, and the impact this has on how we perceive them. There is some interesting stuff on meme theory that I briefly allude to in this blogpost:
    In the case of APD, I don’t think the label was a cynical creation, but rather a response by audiologists to children who complained of listening difficulties but had normal hearing. The problem arose because few audiologists do any research or interact with other professionals, and the category became entrenched without any serious research or discussion with psychologists/speech-language therapists. Once it was there, there was little incentive to give it up, because there are loads of children who can get the diagnosis and then be offered expensive but unproven interventions. One expert states that poor phonological awareness is an indicator of APD, which brings virtually all poor readers into the category.
    I don’t understand why so few audiologists do research. Theirs is a tough scientific discipline requiring knowledge of physics and biology, but with few exceptions they don’t adopt a hypothesis-testing approach.

  6. "I don’t understand why so few audiologists do research. Theirs is a tough scientific discipline requiring knowledge of physics and biology, but with few exceptions they don’t adopt a hypothesis-testing approach."

    When I did research at a medical school, I heard from quite a few people that doctors are glorified technicians. In my opinion as a non-hearing person, audiologists fit that category very well.

    Perhaps they are because in the recent past they had no real tools for scientific research and were almost a branch of the social sciences. In my opinion, the golden hamster as an animal model was the first breakthrough along with better techniques from neurophysiology in general.

    OTOH, most of the audiologists I ran into in the past seemed more wanting to sell me hearing aids than to write down answers to my questions. I couldn't use hearing aids...

    I finally gave up and did my own research. I'll stop here before I start ranting much more. That reference about selling hearing aids shall make this comment anonymous.

  7. I love your stuff and read through some of your other articles. You are spot on with the lack of consistency with children who present for APD as well as wondering why so few audiologists do research.

    As a parent of two children with APD (one is a textbook example), we have tried a dozen programs that are designed for learning/reading difficulties. We've been fortunate to have a learning center nearby that specializes in ADD/ADHD/APD.

    Anecdotally, the most successful program we've used is AIT - Auditory Integration Training. If you're not familiar, it's a ten-day program vs three months or so for other programs. We had three visits to an audiologist during the program and I sat in on all sessions during the training and audilogical testing. The audiologist was AMAZED at the progress from start to finish. She had tested more than ten children who used the program, all with the same results.

    AIT is not "research-based" so ASHA and the school districts discount it. The audiologist was so impressed that there was talk of doing some research to validate the positive results. But then the interest stopped abruptly and we don't know why. It's too bad because I saw the results and they were better than the research-based programs we used.

    The biggest problems for parents of children with learning disabilities are accuracy in the diagnosis and finding programs that are successful in overcoming the disability. If we can get to a point where we can accurately diagnose and treat, it will remarkably help the children, the parents, the schools, and the specialists that work with the children.

  8. The problem here would appear to be the need to have a defined diagnosis with a matching program of support, or remediation.
    I have a diagnosis of Auditory Processing Disorder (APD) as do my three sons and my partner. The diagnosis explains the difficulties we experience on a daily basis, and we have to develop our own ways of working around our deficits.
    There are no magic bullets or remedial programs which would be would appear to part of "deevybee" requirements for recognising APD. The real issue is that currently we do not have the technology to fully understand all of the issues, and this has been reflected in the Medical Research Councils APD research since 2004.
    So the professionals need to hold their hands up nad admit the existance of the APD problems, which the Medical Research Council have been developing a battery of diagnostic tests, while also recognising that there is no specific remedial program or programs which can provide an automatic solution to these issues.
    There have been a great many programs that have made claim to be the cure for APD, but none of which has been able to gain research based recognition.
    So the reality is that APD exists, but that as yet we do not have the technology or full understanding of the underlying causes to be able to suggest a cure. Very much like Autism and Dyslexia, of which APD is one of the many underlying cognitive causes.

  9. My audiology colleague is too engrossed in her hypothesis-based scientific research into APD on a sample of 1100 children to respond to this blog and comments so has asked me, a provider of auditory processing disorder (APD) clinical services, to respond for our specialty.

    There are indeed agreed categories of diagnostic tests for an APD test battery. They are specified in the American Academy of Audiology Clinical Practice Guidelines: Diagnosis, Treatment and Management of Children and Adults with Central Auditory Processing Disorder, August 2010. This is a good starting point for an overview of the field and informed discussion.

    APD is not “a condition of uncertain validity”. At least not if you believe the auditory system extends beyond the cochlea, and as long as you believe that things can go wrong in the brain. There is an extensive neuroanatomical literature on brain lesions, abnormalities and incomplete maturation that give rise to central auditory deficits which collectively comprise APD. (Remember, APD is an umbrella term for these specific deficits, not a singular disorder.) Musiek for example identifies ectopia in the putamen beneath the auditory cortex, superfluous microgyri in the auditory area of the temporal lobe and insufficient corpus callosum myelination as examples of contributors to central auditory deficits. Whitton and Polley report the abnormal tonotopicity in the central auditory cortex following auditory deprivation simulating otitis media. These are just examples from an extensive neuroanatomical, neurophysiological and neuroradiological scientific literature. A modern test battery includes objective, ear-specific and non-language-based tests enabling global or other non-auditory causes for poor test performance to be differentiated.

    With respect to commercial considerations, provision of APD services is sadly the Cinderella of audiology, not the goose that lays golden eggs. But it is true that many non-audiologists promote treatments, almost invariably not evidence-based, for APD. These treatments, such as Auditory Integration Therapy, are given currency by positive anecdotal reports. The placebo effect is powerful, particularly when money and effort have been invested. I am reminded of the past popularity of acupuncture for treatment of profound deafness in children. As a young audiologist I tried unsuccessfully to dissuade parents from investing money in courses of acupuncture treatment though I did gain agreement to carry out pre and post hearing assessments. Naively I produced my audiometric evidence of lack of change in the children’s hearing. Of course every parent dismissed my results and said that their child was hearing much better. Yet 40 years later acupuncture has not displaced hearing aids and cochlear implants.

    There is a vibrant and burgeoning scientific literature in APD. New tests are constantly being developed. Check out the LiSN-S and accompanying treatment software (Listen and Learn) as a good example of a recent adaptive software-based and evidence-based test of a specific important auditory function (spatial stream segregation) with inbuilt controls for language and cognitive level, a method of compensating for peripheral hearing loss, and an evidence-based treatment package. Importantly there is also exciting research evidence of just how treatable APD is (thanks to neuroplasticity).

    So how do you diagnose APD? Following the American Academy Guidelines we test peripheral hearing, screen cognition and language, and carry out an APD test battery consistent with the Guideline. We add the LiSN-S to measure spatial stream segregation ability and delve deeper with more difficult dichotic tests in the 50% of APD cases that show evidence of amblyaudia. We refer to facilities with electrophysiological testing capability when required to rule out auditory neuropathy.

    Evaluation should be followed by deficit-specific treatment. I will outline procedures for that in a separate comment.

    Bill Keith

  10. I understand everyone’s bewilderment at the plethora of treatments on offer for APD and I empathise with parents faced with competing claims that they should try particular treatments, not all evidence-based. But where do you start? Top-down, the three-legged stool approach, metacognitive, bottom-up? The answer is simple. Central deafness is first and foremost a hearing disorder and as with other types of deafness we need to treat the hearing disorder first. As with other types of deafness amplification is one of the most powerful treatment tools.

    Evidence of the benefit of amplification is often first seen in the clinic at assessments when we talk to children with APD via an audiometer. Parents are often astounded or overcome at the immediate improvement in their child’s hearing. Just because the hearing experience*of APD is different in some respects from other types of deafness does not mean that a person with APD does not need amplification. (*To hear an audio simulation of APD look on the News page at

    The most exciting news in APD is the growing literature that consistently shows that amplification in the form of remote microphone hearing aids (usually misleadingly referred to as FM systems) is not only assistive for children with APD (we have long had evidence of that), but can also be therapeutic. Treatment with remote microphone hearing aids has been shown in a number of studies from around the world to improve performance on the following measures (recorded without the hearing aids on): cortical auditory evoked potential amplitudes to tone stimuli, auditory brainstem responses to speech stimuli, frequency discrimination, frequency pattern recognition, phonological awareness, speech perception in noise (same signal source), and spatial stream segregation. The importance of this area of research has just been recognised with the publication of a study on the neuroplastic effects of amplification on children with central auditory deficits in the third most prestigious scientific journal (after Nature and Science) in the world, the Proceedings of the National Academy of Sciences (Hornickel et al 2012).

    It is probably the amplification that drives the neuroplastic change. Think of the auditory brainstem response to clicks in a normal ear at increasing stimulus intensities. As intensity increases the magnitude of the response increases, the morphology improves and stabilises, and the latency decreases. This is all a result of increased synchronicity of neural firing. In central deafness amplification probably improves synchronicity of firing, recruiting more fibres, stimulating more synaptic connections and in time engendering synaptogenesis.

    Amblyaudia treatment is much neglected even though amblyopia in children is routinely treated. Despite the many benefits of amplification there is no evidence that it ameliorates amblyaudia, nor is that our clinical experience. We therefore treat amblyaudia first (if present) using Moncrieff’s ARIA method (four weeks of dichotic auditory training to correct the interaural asymmetry).

    In most cases we next recommend a trial with remote microphone hearing. Our Special Education Adviser visits the child’s school to provide teacher and parent guidance during the trial.

    In cases where the only deficit, or the only deficit other than amblyaudia, is spatial stream segregation we can treat that with the 12 week Listen and Learn software training programme in which case hearing aids are not indicated.

    Once the fundamental hearing deficits have been addressed we can turn our attention to other consequential or comorbid deficit areas such as phonological awareness, language, spelling or reading.

    In our experience children often pass or nearly pass all APD tests after one year of hearing aid treatment, though they tend to want to retain their hearing aids for longer than that.

    It is all good news. New research is constantly improving our ability to diagnose APD, and, thanks to neuroplasticity, it is eminently treatable.

    Bill Keith

  11. References on evidence-based treatments for APD:

    Cameron, Brown, Keith (R), Martin, Watson & Dillon, Development of the North American Listening in Spatialized Noise–Sentences Test (NA LiSN-S): Sentence Equivalence, Normative Data, and Test– Retest Reliability Studies, Journal of the American Academy of Audiology 2009 20(2):128-146

    Cameron S and Dillon H, ‘Development and Evaluation of the LiSN & Learn Auditory Training Software for Deficit-Specific Remediation of Binaural Processing Deficits in Children: Preliminary Findings’, Journal of the American Academy of Audiology (2011) 22 10 678-696

    Friederichs E and Friederichs P, ‘Electrophysiologic and psycho-acoustic findings following one- year application of a personal ear-level device in children with attention deficit and suspected central auditory processing disorder’, Journal of Educational Audiology (2005) 12 31-36

    Hornickel, J., S. G. Zecker, a. R. Bradlow, and N. Kraus, ‘Assistive Listening Devices Drive Neuroplasticity in Children with Dyslexia’, Proceedings of the National Academy of Sciences, 2012

    Johnston, Kristin N, Andrew B John, Nicole V Kreisman, James W Hall, and Carl C Crandell, ‘Multiple Benefits of Personal FM System Use by Children with Auditory Processing Disorder (APD)’, International Journal of Audiology (2009) 48 371-83

    Moncrieff, Deborah W, and Diane Wertz, ‘Auditory Rehabilitation for Interaural Asymmetry: Preliminary Evidence of Improved Dichotic Listening Performance Following Intensive Training’, International Journal of Audiology (2008) 47 84-97

    Moncrieff, DW, ‘Dichotic listening in children: Age-related changes in direction and magnitude of ear advantage’, Brain and Cognition (2011) 76 316-322

    Moncrieff DW, ‘Evidence on How to Diagnose and Treat Amblyaudia, a New Subtype of APD’, Research presentation at American Academy of Audiology Annual Convention, Boston, MA (2012)

    Smart, Jennifer L, Suzanne C Purdy, and Andrea S Kelly, ‘Personal FM Systems for Children with Auditory Processing Disorder – Successfully Fitting This Heterogeneous Population’, in Achieving Clear Communication Employing Sound Solutions – 2008 Proceedings of the First International Virtual Conference on FM (2010) 38-44

    Whitton, JP and and Daniel B Polley, ‘Ear Infection Today, Lazy Ear Tomorrow?’, Audiology Today (2012) 24 4 33-37

    Yip, Fiona and Natalie Rickard, ‘Personal FM Systems in Children with a Spatial Stream Segregation Deficit’, Poster (based on Masters thesis) NZ Audiological Society Conference (2011)

    Bill Keith

  12. Bill: Thank you for taking the time to comment on this blogpost.
    I’m afraid, though, that while I’m glad to hear that attempts are being made to adopt a more rigorous approach to identification and intervention for APD, some of your comments just emphasise to me the fact that the audiology profession has a long way to go. As one who reads a lot of research on children’s developmental disorders in medicine and psychology, the contrast with research quality in audiology is striking.
    You mentioned, for instance, that Musiek has identified ectopias, microgyri and poor myelination in APD. All very plausible, I thought, especially given claims for similar etiologies in dyslexia – see So how had I missed this relevant literature? I checked Web of Science and could not find these reports. I then tried “Musiek ectopia” on Google Scholar. And guess what? I found an article by Gail Chermak in an issue of the Hearing Journal edited by Musiek in which she claimed “Neuroanatomical abnormalities also cause CAPD in children, and result from irregular development of the higher auditory areas and yield abnormal anatomy,” referring to ectopias and polymicrogyria. And the sources for these claims? Erm, the well-known papers on ectopias in dyslexia and SLI, etc by Galaburda and others.
    I agree with you that the LiSN-S has been carefully developed and has a reasonable rationale. But the references that you provided in your final comment don’t reassure me at all about the strong evidence base in this field. You are right to note that placebo effects can be strong, but they aren’t the only thing to worry about. I list a number of other factors that can give a spurious impression of effectiveness in this post:, which explains why simple pre- post-intervention studies are not adequate and randomised controlled trials are essential. Of the 11 studies that you list in the final post, two (Cameron et al 2009; Montcrieff 2011; Whitton and Polley, 2012) don’t focus on intervention of APD, three (Friederichs and Friederichs, 2005; Moncreiff 2012; Yip and Richard, 2011) don’t seem to be in the public domain, and two (Johnston et al 2009; Moncrieff and Wertz 2008) aren’t adequately controlled. That leaves Cameron and Dillon (2011) and Hornickel et al (2012), both of which adopted a randomised controlled design, or something approximating it, but neither of which analysed the data appropriately to demonstrate a significant difference between groups at post-test when pre-test is used as a covariate – see Nieuwenhuis, S. et al (2011). Erroneous analyses of interactions in neuroscience: a problem of significance. Nature Neuroscience, 14(9), 1105-1107. Furthermore, several studies had been funded by a commercial company with a vested interest in positive outcomes.
    Given the length of time that there has been interest in APD, I find it somewhat shocking that there hasn’t been a move towards stronger scientific methodology for evaluating interventions. Children with listening difficulties deserve better.