A proposal to use new diagnostic criteria for autism has roiled the US medical community, with many experts concerned that the move could exclude children affected by some forms of the disorder.
The American Psychiatric Association recommended last month that a new category called "autism spectrum disorder" be established to incorporate several forms of autism which were previously considered separately.
These include autistic disorder, Aspergers disorder, childhood disintegrative disorder and pervasive developmental disorder.
Under this new approach, all four would be considered a variation of autism.
But critics are concerned that this may deprive patients of access to welfare, educational and health services that are based on the old definition set by the APA.
The APA defended its decision, saying that the new criteria establishes degrees of severity for the disorder and would help provide more targetted treatment for patients.
"The proposed criteria will lead to more accurate diagnosis and will help physicians and therapists design better treatment interventions for children who suffer from autism spectrum disorder," argued Doctor James Scully, medical director of the association.
But Fred Volkmar, head of the Children's Psychiatry Department at Yale University, believes this revision would exclude up to 60 percent of children now suffering from Asperger's disorder.
Volkmar said he came to this conclusion by applying the new criteria to a study he conducted in 1993 on children suffering from Asperger's and other forms of autism.
"We went back to the old data, and we looked at the new definition, and we were worried, actually," he told AFP.
"In our work we looked at our preliminary data in high functioning children, Asperger children, and about 60 percent lose their diagnostic. It's huge!"
"They (American Psychiatric Association) say it's not true. I hope it's not true, but they are now in a position of having to respond to this."
According to Geraldine Dawson, chief science officer of Autism Speaks, the largest private foundation in the world dedicated to research of the disorder, it is too early to know "whether there will be or not excluding people who do really have autism spectrum."
But she said her foundation is "committed to funding research that will explore whether or not the criteria are excluding people, and our goal is to insure that ultimately no one is excluded or is denied services."
The proposed changes have been in the works for the past 15 years because studies "show well now that Asperger's disorder is a form of autism," noted Eric Fombonne, chair of the Children's Psychiatry Department at McGill University in Montreal, Canada.
And if the APA decided in 1994 to consider Asperger's separately, it was simply because "at that point we did not know if it was different or just a variation of autism."
Therefore, it was necessary to categorise it separately to study it, he said.