Monday, March 31st, 2014
The latest prevalence estimate of Autism Spectrum Disorder (ASD) – 1 in 68 – reignites conversation that we may be overdiagnosing ASD. In part, to some the estimate just feels too high based on clinical and personal experience. And there is worry that we may be flooding an already overwhelmed evaluation and treatment system.
These concerns echo the debates that surrounded the changes in diagnostic criteria that were introduced in the DSM-5 in May 2013 which, to some, were implemented to protect against overdiagnosis of ASD, as I described last December:
The reformulation of the diagnostic criteria – which led to a discontinuation of the category of Asperger Syndrome in favor of a broad-based category of Autism Spectrum Disorder (ASD) – spurred concerns that many youth would no longer qualify for a diagnosis and hence have their intervention options limited. Others suggested that more precise diagnostic criteria are needed to ensure that ASD does not get overdiagnosed. While we await empirical resolution via publication of well-designed studies, it’s clear that the DSM-5 debate will stand out as an important time in which we wrestled (again) with the best way to be inclusive in diagnosis without expanding diagnostic criteria too broadly.
As a result of the changes in DSM-5, it may be that a few years from now we will see a “recalibration” of the prevalence of ASD. The speculations have been that about 10% of children now diagnosed with ASD will no longer meet criteria.
What do we make of these changing estimates in the prevalence of ASD, which have increased tremendously over the past decade and may, sometime in the near future, begin to decrease? This complex issue does not lend itself to a singular answer. Considering a number of points may help to provide some perspective on how we discuss this question.
PREVALENCE RATES FOR DISORDERS CAN BE “HIGH”
While, as noted above, clinicians, researchers, and policy makers often attempt to interpret the rate of a disorder as a means of ensuring appropriate diagnostics without overdiagnosing, the fact is that there is no magic number or prevalence rate for a disorder. Consider the following:
- Epilepsy is estimated to affect somewhere between 4-10 per 1000 people; and nearly 10% of the population will experience a seizure in their lifetime
- Asthma affects almost 10% of children
- More than 8% of the population is reported to have diabetes
The point? Disorders which can be validated biologically can affect large numbers of people in the population. This means that they are common disorders – not overdiagnosed conditions. The implication for ASD? Simply put, an estimated prevalence of “1 in 68″, in and of itself, does not necessarily imply overdiagnosis.
RATES CAN CHANGE OVER TIME
Part of the concern with the rate of ASD is that it has changed so much over the past decade. The estimates made by the Centers for Disease Control and Prevention (CDC) have gone from 1 in 150, to 1 in 110, to 1 in 88, and now to 1 in 68. The rates of asthma have also gone up over the past decade, though not nearly as dramatically as those for ASD. A combination of factors have influenced this increased prevalence of asthma, including better recognition and diagnosis, changes in the definition of the disorder, and possibly increases in pathogens in the environment. The takeaway here is that an increase in prevalence over time is not a sufficient argument for overdiagnosis.
THE KEY CONCERN IS THE ROOT OF THE INCREASE OVER TIME
The crux of the debate about ASD is that we may be artificially increasing the prevalence. To consider this point, we need to focus on two two related factors that are primarily responsible for the dramatic changes in ASD prevalence.
First, there is much better screening, recognition, and evaluation. This is a positive step forward – early evaluation leads to early intervention. But as noted in the most recent CDC report, there are still children (primarily those in specific ethnic groups) who are not diagnosed at the same “high” rate as others. So simply lowering the bar for early evaluation is not necessarily a good step forward, and in fact may be counterproductive for many children in the population.
Second, there has been an increase in diagnosing “higher functioning” ASD, that is, ASD without a compromised cognitive level. This is where the conversation about overdiagnosis starts – and where the DSM-5 may lead to a reduction in prevalence over time. The sticky point is that as ASD, by definition, is recognized to occur along a spectrum of severity, it becomes hard to know where to draw the line. At what point would we be missing cases that could profit from intervention? At what point are we pathologizing normative variation in social functioning? There is where we need more informative data on the impact of interventions for those diagnosed and more pointed discussion.
Let’s look at a very different example – potential changes in how high blood pressure is being diagnosed in those 60 years of age and older. New guidelines have suggested that the target blood pressure for determining treatment is 150/90, as opposed to 140/90. The result would be that millions of adults over 60 would no longer be “required” to take medication for high blood pressure. This is a current controversy in medicine and it is being debated. The point here is that the biomedical and health sciences have to make these kinds of decisions for many disorders, and that controversies continue to arise. In other words, these are not simple issues, and they are not resolved easily. We continue to gather more information and bring more opinions to the table to come up with our best practices – and this same principle applies to the current and future conversations about ASD.
SO IS ASD BEING OVERDIAGNOSED?
Right now, this is an important question to ask, but rather than demand an answer, we need to gather more informative data and have more informed discussions that go beyond the prevalence rate. We have these discussions frequently about attention-deficit hyperactivity disorder (ADHD), and they continue. We worry that too many kids are being arbitrarily diagnosed with ADHD and that we may artificially inflate rates of ADHD by making inappropriate demands of toddlers and young children. The concern with ADHD is that we may be preventing kids from being kids, slapping them with inappropriate labels, and giving them medications that are not needed.
The concern with ASD is somewhat different. We are not over-medicating youngsters who are receiving a diagnosis of ASD, particularly those who are “high functioning.” We are offering behavioral interventions to improve social and cognitive skills. What we need to know is if some kids who would receive these kinds of interventions don’t need them or don’t profit from them. That’s essentially the tipping point in the argument described above about how to define high blood pressure. We should move beyond the prevalence rate and begin to look more closely at the efficacy of interventions and if there are better ways to define which kids can be best served by a diagnosis.
But what we don’t want to do is arbitrarily decide that the prevalence rate is “too high” and that we need to lower the bar for screening and evaluation. That would be a big mistake and undermine all the progress made to date in early surveillance and early intervention. Whatever the “true” prevalence rate is (and it will be a moving target), what we do know is that many young children can profit from early intervention and that we need to keep momentum going on understanding more about the causes of ASD, how to best diagnosis it, and how to develop even more powerful interventions.
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