Scientists have raised hopes of a cheap and simple test for autism after discovering consistent differences between the microbes found in the guts of autistic people and those without the condition.
The finding suggests that a routine stool sample test could help doctors identify autism early, meaning people would receive their diagnosis, and hopefully support, much more quickly than with the lengthy procedure used in clinics today.
“Usually it takes three to four years to make a confirmed diagnosis for suspected autism, with most children being diagnosed at six years old,” said Prof Qi Su at the Chinese University of Hong Kong. “Our microbiome biomarker panel has high performance in children under the age of four, which may help facilitate an early diagnosis.”
The rate of autism has skyrocketed in recent decades, largely due to increased awareness and a broadening of the criteria used to diagnose the condition. In the UK and many other Western countries, around one in 100 people are now thought to be on the autism spectrum.
Studies in twins suggest that 60-90% of autism is due to genetics, but other factors contribute, such as older parents, birth complications and exposure to air pollution or specific pesticides during pregnancy. Signs of autism range from children who do not respond to their name and avoid eye contact, to adults who find it difficult to understand what others are thinking and become anxious when their daily routine is disrupted.
Scientists have long known that autistic people tend to have less diverse bacteria in their digestive system, but whether this is somehow due to autism, or actually contributes to the condition, is a matter for debate.
To dig deeper into the puzzle, Su and his colleagues analyzed stool samples from 1,627 children aged one to 13, some of whom were autistic. They checked the samples to see which bacteria were present, and did the same for viruses, fungi and other microbes called archaea.
Write in Nature Microbiology, the researchers describe how gut microbes differed markedly in children with and without autism. A total of 51 types of bacteria, 18 viruses, 14 archaea, seven fungi and a dozen metabolic pathways were altered in autistic children. Armed with machine learning, a form of artificial intelligence, the scientists were able to identify the autistic children with up to 82% accuracy, based on 31 microbes and biological functions in the digestive system.
The study also revealed other changes, with several metabolic pathways involved in energy and neurodevelopment appearing to be disrupted in the autistic children.
“While genetic factors play a substantial role in autism, the microbiome may act as a contributing factor by modulating immune responses, neurotransmitter production and metabolic pathways,” said Su. “This does not necessarily imply causation, but suggests that the microbiome may influence the severity or expression of autism spectrum symptoms.”
If the researchers’ thinking is correct, and disruption of the microbiome does affect the severity of autism, it raises the prospect of personalized interventions that use diet or live bacteria known as probiotics to establish a more diverse microbiome in those with the condition. was diagnosed.
“Ultimately, this broad scope increases the potential to develop more effective, non-invasive diagnostic tools and therapeutic strategies for autism,” said Su. The team is now conducting a clinical trial to investigate whether stool samples can help identify autistic children as young as one year old.
Dr Dominic Farsi at King’s College London said the results could have “huge potential” in diagnostic practice, but added that more research was needed to confirm the findings. “Nevertheless, these results may represent a major step towards improving diagnostic methods for autism spectrum disorder,” he said.
Dr Elizabeth Lund, an independent consultant in nutrition and gastrointestinal health, said: “The idea that analysis of stool samples can help with diagnosis is very exciting as there is currently a massive backlog of children and adults waiting to be assessed The current process is very long and there is a shortage of clinicians such as psychologists and psychiatrists who are trained to carry out a proper diagnosis.
“Obviously, the study needs to be replicated by other groups and in other populations around the world, but the approach could provide a new and more automated route to diagnosis in the longer term.”
