New research suggests that a saliva test may one day be able to diagnose autism.

Researchers at Clarkson University and the State University of New York at Plattsburgh found that children with autism spectrum disorder have differences in protein levels in their saliva when compared to typically developing children.

Autism spectrum disorder currently affects one in 68 children in the United States, and the number of people diagnosed with autism continues to rise. Diagnosis is currently made based on behavioral observations, and no biological test for autism exists. A biological test could aid in earlier diagnosis, helping to direct people with autism to interventions.

"We found nine proteins that were significantly elevated in the saliva of the people with autism and three that were lower or even absent," Alisa G. Woods, who is leading the study, said in a statement. "This is the first study to identify these changes in saliva, which is a relatively easy biofluid to obtain for clinical use or research."

The proteins identified primarily have functions in immune system responses or are elevated in people with gastrointestinal problems. The scientists also reported that several of the identified proteins interact with one another.

For the study, researchers studied saliva from six children diagnosed with autism, ages 6 to 16, compared to six typically developing children in the same age range. They used a technique known as mass spectrometry to measure protein differences in saliva taken from the two groups.

"We are the first in the world who proposed a protein complex as a potential biomarker signature, which gives us information not only about the proteins, their relative quantities and their modifications, but also about their interactions with other proteins," Costel C. Darie, a co-lead , said in a statement.

The work is promising for the eventual development of an autism diagnostic test, but more subjects need to be studied to confirm the markers are consistently different in people with autism.

The group plans to further study these protein differences in larger groups of children with autism and also in specific subtypes of autism.

The findings are detailed in the journal Autism Research.