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.
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