A blood test for autism has been developed which could lead to children being diagnosed at an earlier age.
The breakthrough could also lead to new treatments for the disorder by targeting chemicals the test measures.
Identifying youngsters with autism spectrum disorder (ASD) paves the way for parents and doctors to begin treatment earlier.
It can cause a wide range of symptoms from communicating with others to perceiving the world, and affects almost 700,000 Britons.
The new method is said to be “highly accurate” and analyses metabolic biomarkers that predicts whether a child is autistic before behavioural changes begin.
The study published in PLOS Computational Biology looked at specific substances found in a blood sample.
These are produced by chemical reactions known as FOCM (folate-dependent one-carbon metabolism) and TS (transulfuration).
Both of these are altered in children with autism, offering hope of developing a drug that targets them.
Although ASD affects about 1.5 percent of all children, its exact cause remains unknown, and diagnosis requires many doctors specialising in a number of different disciplines.
Previous research has revealed certain differences in metabolic processes among autistic children. But researchers have struggled to translate these into new diagnostic tools.
In the study Professor Juergen Hahn and colleagues used blood sample data from 83 three to ten year olds with autism and 76 peers without the condition.
With the help of advanced modelling and statistical analysis tools, the metabolic data allowed the researchers to correctly classify 97.6 and 96.1 percent of the autistic and ‘neurotypical’ children, respectively.
Prof Hahn said: “The method presented in this work is the only one of its kind that can classify an individual as being on the autism spectrum or as being neurotypical.
“We are not aware of any other method, using any type of biomarker that can do this, much less with the degree of accuracy that we see in our work.”
Prof Hahn said further research is required to confirm the findings.
The team is also hoping to study whether treatments could be used to alter the concentrations of FOCM and TS products and, if so, whether this could impact symptoms of autism spectrum disorder.
Autism has been linked to a number of potential causes, including genes and exposure in the womb to drugs such as sodium valproate, used to treat epilepsy.
But Chinese research suggests obesity may also be a factor. Obese women are nearly 50 per cent more likely to have a child with autism compared with normal weight mothers.
It affects social interaction, communication, interests and behaviour.
Prof Hahn said: “The number of diagnosed cases of autsim spectrum disorder (ASD) has increased dramatically over the last four decades.
“However, there is still considerable debate regarding the underlying pathophysiology of ASD.”
He added: “We emphasise these models are cross validated helping to ensure the results will generalise to new samples.
“The models developed herein have much stronger predictability than any existing approaches from the scientific literature.”