London - A blood test could help to diagnose autism in children by detecting early warning signs.
It is almost 90 percent accurate and could be available to doctors within a year, scientists at the University of Warwick say.
Their test, which delivers a result within four hours, is believed to pick up damage in the blood that mirrors brain problems linked to autistic symptoms.
Study leader Dr Naila Rabbani said: "We have been working for five years on this test, believing it would be beneficial to children and their parents to identify the problem and provide intervention therapy at an earlier point.
"More research is needed to identify if the same biomarkers are found in younger children, but we are determined to take this forward to the level where it could be available on the NHS."
Children are principally diagnosed by judging speech and communication problems, which is difficult for doctors as autism affects people differently.
Hopes of a physical test in recent years have focused on scans that could pick up a difference in brain size or faulty connections in the area that processes language.
The Warwick researchers worked with the University of Bologna in Italy to recruit 38 children with autism spectrum disorder, aged five to 12, along with 31 healthy children of the same age.
They found autistic children have damage to the proteins in their blood plasma, caused by sugar and harmful molecules containing oxygen.
Blood and urine test results were used to develop systems for a computer to diagnose autism based on biological signs. The best system was correct for 36 out of the 38 children with autism, and had an overall accuracy of up to 88 percent.
It produces a means of determining whether autism is likely to be present, and researchers hope to trial it next on two-year-olds.
Dr Rabbani, reader of experimental systems biology at the University of Warwick, said: "Our discovery could lead to earlier diagnosis and intervention. We hope the tests will also reveal new causative factors.
"With further testing we may reveal specific plasma and urinary profiles or “fingerprints” of compounds with damaging modifications."
Autism spectrum disorders, such as Asperger syndrome, mainly affect a person’s social interaction and communication, with symptoms including speech disturbances, compulsive behaviour, hyperactivity and anxiety.
Genetic causes are thought to be responsible for around a third of autism spectrum disorder cases, while the rest are believed to be caused by a combination of environmental factors and genetic mutations and variants.
The study is published in the journal Molecular Autism.