New research offers what could become a surprising way to diagnose whether a child has autism: Simply check the makeup of their gut microbiome.

In a study published July 8 in the journal Nature Microbiology, scientists analyzed more than 1,600 stool samples from children ages 1 to 13 and found several distinct biological “markers” in the samples of children with autism. 

The finding means that unique traces of gut bacteria, fungi, viruses and more could one day become a diagnostic tool, lead study author Qi Su, a researcher at the Chinese University of Hong Kong, told the New York Times.

Such a tool could help professionals diagnose autism sooner, quickly getting children treatments that are more effective at younger ages, he added.

The idea was tantalizing to some experts.

“Too much is left to questionnaires,” Sarkis Mazmanian, a microbiome researcher at the California Institute of Technology, told the Times. “If we can get to something we can measure — whatever it is — that’s a huge improvement.”

For decades, researchers have searched for a reliable indicator of autism, with limited success. The U.S. Food and Drug Administration (FDA) has approved two diagnostic tests based on eye-tracking software, the Times reported.

Some researchers have more recently started investigating whether human stool, which offers a window into the trillions of fungi, bacteria and viruses living in the intestines, might offer a new way to diagnose the disorder. 

Still, the concept that the gut microbiome might play a role in the development of autism remains controversial among researchers, Gaspar Taroncher-Oldenburg, a microbiologist who published a landmark study on the subject last year, told the Times.

He called the most recent study an “important milestone” in the broader acceptance of this line of research. 

“There is a changing of the winds,” he said. “People are now accepting that the microbiome is not just part of this, but it might be a fundamental piece of the puzzle.”

In the new study, researchers identified major biological differences between the stool of children with autism and other samples.

Contrary to past research, the investigators decided to look at other microorganisms in the gut besides bacteria, including fungi, archaea and viruses, as well as related metabolic processes. 

What did they find? The scientists identified 31 biological signatures that distinguished the groups.

Then, in a new group of stool samples, they checked whether those markers could correctly identify which stool samples were from someone with autism. Su said the model made the correct predictions nearly all of the time.

But Mazmanian, who was not involved in the new paper, said he wanted to see studies clarifying exactly how the microbiome was related to autism and whether it played a significant role in causing the disorder.

Some researchers also argue that this relationship goes the other way: Children with autism are more likely to be “fussy eaters,” changing the makeup of their microbiome, the Times reported.