Friday, July 01, 2005

Autism Spectrum Disorder diagnostic tool

Two MU researchers are changing the face of autism diagnosis.
Judith Miles, a professor of child health genetics, and Nicole Takahashi, a senior research specialist, have developed a diagnostic tool that will classify autistic children into two subgroups, essential autism and complex autism.
“This is really the first distinction you should make if you’re evaluating a child with autism,” Miles said. “Knowing whether a child has complex or essential autism allows you to provide both a more accurate prognosis and recurrence risk.”
After a five-year study involving a sample of 260 autistic children, the researchers concluded that 30 percent of the autistic population has complex autism. These children have a small head size or a collection of at least six abnormal physical features, as well as the common symptoms found in all children with autism. These include impaired social interaction, language difficulty and a tendency for repetitive behaviors.
“We found that the children with complex autism were different genetically,” Miles said. “Their recurrence risk with their siblings was less and they had a more normal male-to-female ratio. You generally read that the sex ratio is four or five males to every female.”
Miles and Takahashi found there is a nearly one-to-one ratio for children with complex autism. For children with essential autism, there are about seven males to every female.
The researchers also found that children with complex autism are more prone to seizures, lower IQs and structural anomalies in the brain than those with essential autism. Children with essential autism, who constitute the remaining 70 percent, have the common social and language symptoms without the physical abnormalities of complex autism.
“In addition, we found that the children with essential autism are very rarely going to have abnormal chromosomes or other genetic tests, so you don’t have to do as many tests on that group,” Miles said. “It’s a cost-savings for families and society.”
Miles said their findings will also serve parents in learning what to expect for their autistic children. Takahashi said the study will help with future research in the field.
“A lot of gene-finding studies haven’t found anything because they’re looking at a big heterogeneous group — a mishmash of people with different etiologies,” Takahashi said. “So we think this is really important for everyone to follow — to do that initial split of complex or essential — and cutting out the complex group will, we think, greatly increase the power of genetic studies so people can really start finding some autism genes when looking at a more homogenous group.”
The study, which was sponsored by the Sears Trust, the National Institutes of Health, the Missouri Department of Mental Health and the National Association for Autism Research, was published in the June issue of the American Journal of Medical Genetics.
The researchers have begun using the diagnostic tool at MU’s autism clinic and are developing a measure that other physicians can use.
About 24,000 children born in the United States each year will eventually be diagnosed with autism or an autism spectrum disorder, according to the Centers for Disease Control and Prevention. Autism spectrum disorders include autism, Asperger’s disorder and other pervasive developmental disabilities.
Miles doesn’t have an exact count of children in Columbia with the disorder because true incidence rates are nearly impossible to detect. However, she said the prevalence of the disorder — that is, the number of children diagnosed — has tripled in the last 15 years.
“We don’t know whether the prevalence numbers that we’re looking at now means the number of people diagnosed reflect changes in our diagnostic criteria, which have certainly changed over the last 15 years, whether families, schools and health professionals are just more tuned in to the diagnosis, or if there really is an increase in the true incidence of the disorder,” Miles said.
William Thompson, an alumnus, and his wife, Nancy, gave $8.5 million to MU in April to establish the Thompson Family Center for Autism and Neurodevelopmental Disorders. Miles is the director for the autism clinic, which will become part of the research center.
“Our clinic has a dual mission,” Miles said. “It has a mission to provide service for families — giving people diagnosis and treatment, supporting families, medical care. The second mission is research, to learn more so we can help kids do better.”