The study findings were reported today at the 4th International Meeting for Autism Research in Boston. Some 700 scientists from around the world were expected to attend the conference.
"Finding a sensitive and accurate biological marker for autism that can be revealed by a simple blood test would have enormous implications for diagnosing, treating and understanding more about the underlying causes of autism," researcher David Amaral, PhD, said at a news conference.
Because the diagnosis of autism is now made by observing behavioral traits, most children with the disorder are not identified until after age 2. Increasing awareness of the importance of early treatment has made earlier diagnosis a top priority in autism research.
The study, conducted by Amaral and colleagues at the UC Davis MIND Institute, involved analysis of blood samples from autistic and normally developing children using newly available technology.
Seventy children between the ages of 4 and 6 were recruited for the study, along with 35 children in the same age group without autism.
Amaral said the blood analysis revealed "very striking differences" in the blood of the autistic and normal children with regard to the production of proteins and cells associated with immune function.
Of the roughly 4,000 different proteins evaluated, the testing identified about 500 differences in proteins between the autistic and normally developing children. About 100 of these protein variations were large enough to suggest a real difference between the two groups, Amaral said.
But he cautioned that the differences identified so far may not directly lead to a diagnostic blood test for autism. Rather, he said, they suggest that researchers are on the right track in their search.
"I think this gives us confidence that this is a good strategy," he said, adding that new technology should allow researchers to identify a pattern of protein differences that will be the basis of a simple blood test.
The Role of the Immune System
Amaral and colleagues also reported differences in the cells associated with the immune system. These findings, along with those from another UC Davis MIND Institute study reported at the conference, lend support to the idea that the immune system plays an important role in autism.
The second study, which involved 30 children with autism and 26 normally developing children between the ages of 2 and 5, revealed clear differences in immune system reactions between the two groups.
But researcher Judy Van de Water, PhD, says carefully controlled trials are needed to determine whether these immune system differences lead to autism.
One theory is that environmental triggers contribute to autism in children who are genetically vulnerable to the disorder. The hope is that identifying these triggers and the children who are most vulnerable to them can make a big difference in outcome.
"This [research] is part of a larger effort to learn how changes in immune system response may make some children more susceptible to the harmful effects of environmental agents," says National Institute of Environmental Health Sciences director Kenneth Olden, in a news release.