Researchers say they are one step closer to developing a biological test for autism.

In a study published online this week in the journal Autism Research, researchers report they that were able to use a magnetic resonance imaging, or MRI machine, to take a brain scan from which they can accurately distinguish individuals with high functioning autism from those without in 94 percent of cases.

Though preliminary, experts say the finding is significant because it could allow for a more accurate and earlier diagnosis of autism. Traditionally, the disorder is diagnosed based on clinical observations of an individual’s development and behavior.

“This is not yet ready for prime time use in the clinic yet, but the findings are the most promising thus far,” said Nicholas Lange, an associate professor of psychiatry at Harvard who led the study.

Lange and his colleagues took brain scans of 60 individuals, 30 with high functioning autism and 30 without. By focusing on six aspects of the brain’s circuitry, they were able to identify who had autism and who did not almost perfectly.

A secondary study using a different set of subjects confirmed a similar rate of success.

Further research will be conducted to assess the effectiveness of brain scans to distinguish individuals with more severe autism, younger children with the disorder and those with other conditions like attention-deficit hyperactivity disorder, or ADHD, and obsessive–compulsive disorder, researchers say.