M. Spencer Green, Associated Press
In this photo taken Thursday, Sept. 8, 2011, Marc Lazar, autism specialist for Aspiritech, a nonprofit enterprise that specializes in finding software bugs, works with employee Alan Sun, as they test a new program in Highland Park, Ill. Aspiritech hires only people with autism disorders. Traits that make great software testers _intense focus, comfort with repetition, memory for detail _ also happen to be characteristics of autism. (AP Photo/M. Spencer Green)to be characteristics of autism.

The rate of autism — which has grown fast for three decades — may soon be checked. But the slowdown won't come through prevention and better treatments. If it happens, it will likely result from efforts to redefine the disorder itself, according to an analysis released Thursday.

An expert panel assembled by the American Psychiatric Association is considering proposed changes that would tighten the definition as part of an update of the group's Diagnostic and Statistical Manual of Mental Disorders. That guide is a standard reference that helps experts make diagnoses and insurance companies and policymakers decide coverage, among other things.

A preliminary analysis released during a meeting of the Icelandic Medical Association says that a tightened definition of what constitutes autism could put health, education and social services out of reach for some families.

Critics of the current definition, however, say it's too vague and unnecessarily inflates the number of people with autism.

A series on autism in the Los Angeles Times last month noted that in the past two decades, the incidence estimates have "climbed twentyfold." Experts, it noted, say the increase could be because of expanded definitions of the disorder and "more vigorous efforts to identify it."

Other statistics have put the incidence of autism at about 1 in 100 children. Last year, the Los Angeles Times wrote about a South Korean study that indicated as many as 1 in 38 people have autism. The incidence may be similar in the United States, the authors noted.

Autism spectrum disorders are complex brain disorders. According to Autism Speaks, they are marked by varying degrees of difficulty with social interaction, communication and repetitive behaviors. The spectrum currently includes autism, Rett syndrome, childhood disintegrative disorder, pervasive developmental disorder-not otherwise specified (PDD-NOS) and Asperger Syndrome. It says that "ASD can be associated with intellectual disability, difficulties in motor coordination and attention and physical health issues such as sleep and gastrointestinal disturbances."

Dr. Fred R. Volkmar, director of the Child Study Center at Yale University School of Medicine and one of the authors of the just-released analysis

told the New York Times that "The proposed changes would put an end to the autism epidemic. We would nip it in the bud — think of it that way."

How many people would be excluded if a new definition was used in making diagnoses has been contested. One member of the task force considering the change, Dr. Catherine Lord, director of the Institute for Brain Development, said fewer people would be excluded from the diagnosis than the analysis says. Under consideration is removing Asperger syndrome and PDD-NOS as separate entries. The proposed change would, instead of requiring someone to exhibit six of 12 behaviors, allow diagnosis of autism spectrum disorder for individuals if they had three deficits in social interaction and communication and at least two repetitive behaviors.

The analysis of the proposal's effects by Volkmar's team used 1993 study data. They found of 372 children and adults who were among the highest-functioning, only 45 percent would qualify as having autism spectrum disorder with the new definition. That they focused solely on high-functioning may have "slightly exaggerated the percentage" that would not be diagnosed that way, they told the New York Times. But they said their analysis showed one-fourth of those with classic autism, three-fourths with Asperger's and 85 percent with PDD-NOS wouldn't be so diagnosed.

Autism Speaks notes that there is no definitive medical test for autism; instead, physicians rely on the "Modified Checklist of Autism in Toddlers" to help with diagnosis.

The manual's revisions will be done by the end of the year.

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