A new study published in the journal Archives of General Psychiatry suggests that the current gold standard of “best-estimate clinical diagnoses” for the diagnosis of autism spectrum disorders may not be the best method of diagnosis. Under the current method, clinicians commonly perform a variety of tests, use scales and information from observations as well as parent interviews to classify individuals into subcategories listed in standard psychiatric diagnostic manuals, however, according to the study, these diagnosing tools are widely available across centers which leads researchers to suggest that this may not be the best method to diagnose autism spectrum disorders.

Lead researcher Dr. Catherine Lord, director of the Institute for Brain Development, a partnership of Weill Cornell Medical College, New York-Presbyterian Hospital and Columbia University Medical Center explains:

“Clinicians at one center may use a label like Asperger syndrome to describe a set of symptoms, while those at another center may use an entirely different label for the same symptoms. This is not a good way to make a diagnosis. Autism spectrum disorders are just that — a spectrum of disorders. Instead of using subcategories, it would be better to simply report the results from agreed-upon tests and scales. This approach would provide more consistent and accurate information about individual patients.”

The new study, funded by the Simons Foundation and the National Institute of Mental Health, supports earlier evidence that standardized diagnostic instruments accurately predict individuals affected by autism and who will continue to have it over time. The researchers also agree with recent skepticism regarding the value of categorical groupings of autism spectrum disorders in standard diagnostic manuals, like the Diagnostic and Statistical Manual of Mental Disorders – IV – text revision (DSM-IV-TR) and the International Statistical Classification of Diseases.

Dr. Lord comments: “There has been a lot of controversy about whether there should be separate diagnoses for autism spectrum disorder, especially Asperger syndrome. Most of the research has suggested that Asperger syndrome really isn’t different from other autism spectrum disorders.”

Dr. Lord and co-author Dr. Eva Petkova, a biostatistician at NYU, recruited approximately 2,100 participants aged between 4 and 18 years from the Simons Simplex Collection, a multi-site project aimed at studying de novo genetic variations in families affected by autism spectrum disorders, who were diagnosed with an autism spectrum disorder by clinicians at 12 university-based centers. The clinicians, all experts in autism spectrum disorders, were trained on how to perform and score the same set of cognitive tests and standardized instruments to assess social and communication skills and repetitive behavior. The training included the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview — Revised (ADI-R) but did not include specific training in making best-estimate clinical diagnoses. The participants were classified into three categories of varying severity, i.e. autistic disorder, pervasive development disorder not otherwise specified (PDD-NOS) and Asperger syndrome by using the DSM-IV-TR.

The researchers observed dramatic variations in specific categories of autism spectrum disorders from site to site across the country, for example, clinicians at one site only diagnosed autistic disorder, whilst those at other sites made this diagnosis in fewer than half of the participants. When assessing variations in diagnoses, researchers discovered that after variations in social and communication deficits, the second most significant variation factor was Asperger syndrome, with the number of individuals diagnosed ranging from zero to almost 21% across all sites. They note that measured by standardized instruments, there were no significant variations in individuals with autism spectrum disorders in terms of demographic information or developmental and behavioral characteristics.

Dr. Lord comments: “The labels are pretty meaningless, because people are using the same general terms as if they mean the same thing, when they really don’t. Because clinicians may not be using labels appropriately or diagnosing accurately, they may not be getting a sense of children’s strengths and weaknesses and what therapy is best for them.”

They discovered that clinicians across centers varied in their assessment of weighing different factors and in the thresholds they set to diagnose individuals.

They noted that despite most centers being strongly influenced by verbal IQ levels in their diagnoses, each site used remarkable differences in the cutoff points to classify individuals into specific categories. The same dramatic effects applied to age on diagnoses and the specific age cutoff points across sites.

Lord declared: “This doesn’t make sense. You don’t want to be told that you have a cold if you’re 7 and a bacterial infection if you’re 12, when you present with identical symptoms.”

According to Dr. Lord the variability in clinical diagnoses could reflect regional differences, for example, services in some regions may be available only to children diagnosed with autistic disorder, but this same diagnosis may be stigmatizing or limit school options in other regions. She adds that clinicians may also vary in evaluating individual’s irritability levels and hyperactivity when judging the severity of autism spectrum disorder.

Dr. Lord suggests that the use of standard diagnostic manuals to classify individuals into subcategories of autism spectrum disorder should be reconsidered in light of the inconsistencies in best-estimate clinical diagnoses, and concludes, “It’s very important for clinicians to use information from dimensions that directly relate to autism spectrum disorders, in addition to verbal IQ and the level of irritability and hyperactivity. The take-home message is that there really should be just a general category of autism spectrum disorder, and then clinicians should be able to describe a child’s severity on these separate dimensions.”

Dr. Gerald D. Fischbach, scientific director of the Simons Foundation Autism Research Initiative comments: “This is an extremely important paper regarding our understanding of the various components of autism spectrum disorder from a group that has been crucial in defining the features of autism over many years. They call attention to quantifiable traits rather than existing diagnostic categories. We are proud to have funded this project and to have gathered the Simons Simplex Collection on which this study is based under Dr. Lord’s leadership.”

Building on her previous pioneering efforts in developing these commonly used scales, Dr. Lord’s future research lies in working on improving diagnostic instruments to make them shorter, simplify them for easier use, and to make them more appropriate for a wider variety of patients. She will also assess whether certain dimensions are really distinct from one another.

Additional collaborating institutions include Columbia University Medical Center in New York City; the Simons Foundation in New York City; the University of Michigan in Ann Arbor; Emory University School of Medicine in Atlanta, Ga.; Emory University School of Medicine and Marcus Autism Center, Children’s Healthcare of Atlanta, Ga.; Children’s Hospital of Philadelphia in Pennsylvania; the University of Washington in Seattle; Vanderbilt University Medical Center in Nashville, Tenn.; Harvard Medical School in Boston, Mass.; the University of California, Los Angeles; Montreal Children’s Hospital in Quebec, Canada; the University of Missouri in Columbia; Baylor College of Medicine in Houston, Texas; the University of Illinois at Chicago; Cincinnati Children’s Hospital Medical Center in Ohio; the University of Minnesota in Minneapolis; and Indiana University in Bloomington.

Written by: Petra Rattue