A new blood test can determine whether a child is on the autism spectrum before they turn two, it has been claimed.
Researchers in New York say by analysing biomarkers in a child's blood they can diagnose it with 96 percent accuracy.
"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," says study author Juergen Hahn.
Normally children are not diagnosed until they are at least two, if not older, because diagnosis largely relies on analysing a child's behaviour and developmental progress.
Often children with high-functioning autism - or related conditions such as Asperger syndrome - aren't diagnosed until well after starting school, when they struggle to make friends or cope with structured classes.
It's estimated around 65,000 Kiwis are on the autism spectrum, with 80 percent of them male.
Dane Dougan, CEO of Autism NZ, told The AM Show on Friday the discovery is "pretty exciting".
"It takes away all the subjectivity of a diagnosis. Although that is done by experts and it's reasonably accurate, this is an objective test."
Mr Dougan says it can take 18 months to get a diagnosis through the public health system, then another 12 to 18 months to start getting proper support - but the earlier a child can get help, the better the outcomes.
"What parents tell us is you get given a couple of flyers, patted on the back and wished all the best," he said.
"The behavioural support is one of the key type support families and children need. If they get that behavioural support, then hopefully they'll go on to live lives like you and I live - get married, have kids, have jobs."
Researchers at the Rensselaer Polytechnic Institute in New York used sample data from 83 children with autism and 76 without. By measuring for substances produced by two metabolic processes - folate-dependent one-carbon metabolism and transulfuration pathways - they were able to identify 97.6 percent of kids with autism, and 96.1 percent of those without.
"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," says Dr Hahn.
An early diagnosis will allow more time for health professionals to determine what kind of support a child needs, as every person with autism has unique needs.
"If you've met one person with autism, you've met one person with autism," says Mr Dougan, quoting autistic author and university professor Stephen Shore.
"This could make a huge difference. If children can be diagnosed prior to the age of 12 months, it means we can start helping them."