Proposed changes to the definition of autism might make it much harder for a person to be diagnosed with the disorder. The change would likely slow the rapidly increasing rate of autism diagnoses but also spark  fears that some children with autism  would  no longer fit its definition, excluding them from services and treatments they depend on.

A panel of experts from the American Psychiatric Association re-evaluating the definition currently published in the "bible" of psychiatry, the Diagnostic and Statistical Manual of Mental Disorders, which is used to determine treatment, insurance coverage and access to services for a variety of mental illnesses.

That definition includes a number of disorders under the umbrella of autism spectrum disorder, including autism disorder, Asperger's disorder and  pervasive development disorder not otherwise specified, which usually includes people who don't fit neatly into the other categories of autism. Currently, people must show at least six out of 12 possible behaviors to be diagnosed as autistic.

According to a report published Wednesday in the New York Times, proposed changes to the definition for the new DSM edition, slated to be published next year, would exclude Asperger's and PDDNOS and consolidate autism diagnoses under a narrower category of autism. The person would have to show three deficits in social interaction and communication and two repetitive behaviors, a stricter set of criteria.

Many autism experts support the proposed changes, saying they  will make it far easier to diagnose autism.

"Distinctions between the current subtypes are difficult to make, and do not necessary have differential implications for treatment. The line between PDDNOS and autism is often blurry, as is the line between Asperger's disorder and 'high functioning' autism," Wendy Stone, director of the University of Washington Autism Center, told ABC News. "Even well-trained researchers and clinicians using standardized measures may not agree on which side of these 'lines' an individual may fit."

Experts say the changes will probably also arrest the rate of autism diagnoses, which have been rising  sharply  in recent years. The Centers for Disease Control and Prevention estimates that one in 110 children in the U.S. has autism under the old definition.

Dr. Fred Volkmar, director of the Child Study Center at the Yale School of Medicine, led a team of researchers who analyzed data from a 1994 study testing the criteria used in the current edition of DSM. According to a statement from Yale University, the researchers found that half of the people diagnosed with autism in that trial would no longer merit a diagnosis under the new proposed criteria.

In the statement, Dr. Volkmar emphasized that these preliminary findings suggest that "only the most cognitively able" would be excluded from an autism diagnosis.

Lori Warner, director of the Hope Center for Autism at Beaumont Children's Hospital Center in Royal Oak, Mich., told ABC News that these cognitively able, 'high-functioning' autistics still require a number of treatment and support services.

"People tend to think that the more severely impacted children need the most services. But often these high-functioning individuals with enough help could either move out of the spectrum or live more functional lives with dignity," Warner said.  "If the Volkmar group is correct, I'm very worried for that segment of families."

If patients lose their diagnosis status, they might not be able to get the treatments and services provided for autistic patients and their families, which often require a diagnosis to qualify for insurance coverage, special education and other assistance.

"Really, in a lot of states, you need that diagnosis in order to have treatment covered. If you don't have that diagnosis, you're going to try to pay out of pocket or you have no access to these services," Warner said. "It could be devastating for a lot of families."