April 11, 2012 — Revised diagnostic criteria for autism may have a significant impact on the proportion of individuals who qualify for a diagnosis of autism spectrum disorder (ASD), new research suggests.
A study conducted by investigators at Yale University examining the impact of proposed changes to the diagnostic criteria for ASD in the upcoming fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5) suggests that if implemented, up to 40% of those with autism as defined by the current criteria would be excluded from such a diagnosis, raising concerns that a significant proportion of individuals may be excluded from medical and social services.
"Proposed DSM-5 criteria could substantially alter the composition of the autism spectrum. Revised criteria improve specificity but exclude a substantial portion of cognitively able individuals and those with ASDs other than autistic disorder.
"A more stringent diagnostic rubric holds significant public health ramifications regarding eligibility and compatibility of historical and future research," the investigators, led by James C. McPartland, PhD, Yale Child Study Center, New Haven, Connecticut, write.
"Given the potential implications of these findings for service eligibility, our findings offer important information for consideration by the task force finalizing DSM-5 diagnostic criteria," Fred Volkmar, MD, director of the Yale Child Study Center and senior author of the study, said in a statement released by Yale University.
Originally presented in January at a meeting of the Icelandic Medical Association, the study is published in the April issue of the Journal of the American Academy of Child and Adolescent Psychiatry.
APA Fires Back
However, the findings have drawn fire from the American Psychiatric Association (APA), specifically the DSM-5 Work Group on Neurodevelopmental Disorders, which defends proposed revisions to the diagnostic criteria and claims the study by the Yale investigators has significant limitations.
By suggesting that many people would be excluded from a diagnosis, the study has generated "attention-getting media" and has caused unnecessary fears that many people who now have a diagnosis of autism will have that diagnosis taken away, Work Group member Bryan King, MD, University of Washington and Director, Seattle Children's Autism Center, Seattle, told Medscape Medical News.
In a related commentary, Dr. King and other Work Group members, led by Susan E. Swedo, MD, who is a senior investigator with the National Institute of Mental Health, go on to note that the most important limitation of the study by McPartland et al is that it used data archived from a field trials study for the DSM-IV.
"The original sample was not representative of a general medical or psychiatric clinic, much less of the general population, and cannot be generalized to apply to other datasets, such as the DSM-5. Moreover, the methodology used for the original collection of the field trials data severely limited their applicability to an analysis such as the one attempted by McPartland et al," they write.
In the study, the researchers focused on a sample of 933 participants evaluated during the DSM-IV field trial. Of these participants, 657 had a clinical diagnosis of an autism spectrum disorder (ASD).
Using the DSM-5 diagnostic criteria for ASD, the investigators found that 60.6% (n = 398) of individuals with a clinical diagnosis of an ASD met the new criteria (95% confidence interval [CI], 57% - 64%) and that 39.4% (n = 259) did not.
The study also showed that the overall specificity of the DSM-5 diagnostic criteria for ASD was high, with 94.9% (95% CI, 92% - 97%) of individuals accurately excluded from the spectrum.
Individuals with lower cognitive ability (ie, IQ < 70) were more likely to meet the DSM-5 criteria for ASD than individuals with high cognitive ability (IQ > 70; P < .001).
The researchers found other discrepancies in cases meeting the DSM-5 criteria with regard to the type of ASD. For example, 25% of patients with Asperger's disorder and 28.3% of patients with atypical autism or pervasive developmental disorder not otherwise specified (PDD-NOS) met the proposed DSM-5 criteria.
Most individuals who failed to meet the proposed criteria failed because they did not meet the social communication criterion (27%) or the restricted, repetitive behaviors (RRB) criterion (22%).
"The modifications proposed to diagnostic criteria for ASD appear to result in a more stringent diagnostic threshold," Dr. McPartland and colleagues write.
"According to the proposed criteria, cognitively able individuals and those with ASDs other than autistic disorder would be less likely to receive a diagnosis on the autism spectrum," they add.
They conclude that the changes "could exert detrimental effects on service eligibility and the ability of researchers to integrate information from autism research to date with that conducted under the proposed criteria."
However, said Dr. King, the study was flawed and its conclusions inaccurate.
"There were lots of problems with this paper. It's great to raise questions about the criteria, but let's be careful about putting headlines in the newspapers about all of the disasters that are going to happen, because your study does not allow you to make those claims."
Dr. King was referring to a news story in the New York Times that had the headline, "New Definition of Autism Will Exclude Many, Study Suggests."
Dr. King said that the study authors did not try to calm the waters. "They didn't back away. They were stoking the flames."
He also pointed out that the new criteria are actually being expanded to include people in younger and older age groups that are currently difficult to diagnose with the existing criteria.
"If you get down into the weeds of what the actual criteria look like, I think people will see that we're not setting the bar higher. If anything, we're trying to lower it," Dr. King said.
Higher Functioning Patients Excluded
David H. Skuse, MD, professor of behavioral and brain sciences at the Institute of Child Health in London, UK, and author of an accompanying editorial in the same issue of the Journal of the American Academy of Child and Adolescent Psychiatry told Medscape Medical News he believes the proposed revisions to the ASD diagnostic criteria for a diagnosis of autism are "generally" an improvement.
"There are several excellent recommendations: I agree with the dimensional approach to diagnosis, the combining of the social and the language aspects of the definition into one set of criteria, and the removal of the subtypes of autism spectrum disorder such as Asperger syndrome," Dr. Skuse said.
"However, the main problem with the approach in my view is that people with normal or high IQ may in future be excluded from the spectrum because they do not have sufficient [evidence] of the following mandatory set of criteria, including stereotyped or repetitive speech, motor movements or use of objects; excessive adherence to routines, ritualized patterns of verbal or nonverbal behavior or excessive resistance to change; highly restricted, fixated interests; and hyper- or hyporeactivity to sensory input or unusual interest in sensory aspects of environment," he said.
Dr. Skuse added that these criteria were not mandatory under DSM-IV and pointed out that they are "almost certainly associated with low IQ, hence people with higher IQ will fail to meet criteria for an autism spectrum diagnosis in the future, and that will include many cases currently diagnosed with Asperger syndrome and with a diagnosis of PDD-NOS [pervasive developmental disorders not otherwise specified]. The McPartland et al article strongly implies that it is the 'higher functioning' individuals who will differentially fail to meet criteria for ASD."
In his view, all social-communication impairments of an autistic type should be regarded as being on the autism spectrum, "because these are almost always the impairments that lead to social and educational problems — whether or not they are associated with the symptom sets mentioned previously."
The study by McPartland et al was supported by the National Institute of Mental Health (NIMH). Dr. McPartland has received research support from the National Institute of Child Health and Human Development, the Simons Foundation, the National Alliance for Research on Schizophrenia and Depression, and the National Institute of Mental Health. He reports financial relationships with Guilford Press and Lambert Academic Publishing and that he has received lecture honoraria for presentations on autism. Dr. Volkmar reports that he has received lecturer honoraria for presentations on autism and that he receives book royalties from several publishers and serves as editor of the Journal of Autism and Developmental Disorders. Dr. King has disclosed no relevant financial relationships. Dr. Skuse reports that he is a stockholder in IXDX Ltd., which is responsible for the distribution and sales of the 3Di interview for the assessment of autistic disorders.
Medscape Medical News © 2012 WebMD, LLC
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Cite this: Proposed New Definition of Autism Stirs Controversy - Medscape - Apr 12, 2012.