New evidence from two separate studies suggests that autism could be detected in infants, research that physicians hope will lead to early treatment or even prevention.

In the first study, researchers say there is evidence of immune and protein alterations in the blood samples of autistic children, raising hopes for earlier diagnoses.

Scientists from the UC Davis M.I.N.D. Institute announced the research at the 4th International Meeting for Autism Research in Boston on Thursday, saying the evidence could be a major step toward developing a routine blood test that would allow autism to be detected in newborns.

According to the statement by the Institute, autism is currently diagnosed through a series of behavioural observations, which are not reliable until the child is between two and three-years-old.

"Finding a sensitive and accurate biological marker for autism that can be revealed by a simple blood test would have enormous implications for diagnosing, treating and understanding more about the underlying causes of autism," David G. Amaral, research director at the Institute and one of the co-authors of the paper, said in a statement.

"Not being able to detect autism until a child is close to three-years-old eliminates a valuable window of treatment opportunity during the first few years of life when the brain is undergoing tremendous development."

Researchers took blood samples from 70 children with autism who were between 4 and 6 years old and from 35 children of the same age who didn't have the disorder.

"From these results we think it is highly likely that there are differences we can detect in blood samples that will be predictive of the disorder, though we are still some years away from having an actual diagnostic blood test for autism" Amaral said.

The scientists also say further studies need to be conducted to confirm the findings in a larger sample and also with younger children.

The study raises hopes that not all children with autism are doomed to live with the disorder Amaral said.

"It may be that some children have a vulnerability -- such as a genetic abnormality -- and that something they encounter after being born, perhaps in their environment, triggers the disorder. Studying the biological signs of autism could lead to new ways to prevent the disorder from ever occurring."

Even if it cannot be prevented, Amaral says early intervention could improve "the lifetime outlook for children with autism, particularly those who now respond poorly to therapy initiated when they are three or older."

Behaviour indicators in infants

In another study published this month, Canadian researchers have pinpointed specific behavioural indicators in infants that may predict whether they will develop autism.

The infants studied are the younger siblings of children who are already diagnosed with autism. Studies show that families with one autistic child have a roughly 5 to 10 per cent chance of a second child being diagnosed with autism.

The preliminary findings were published this month in the International Journal of Developmental Neuroscience.

The Canadian study, which began as a collaboration of McMaster University's Offord Centre for Child Studies in Hamilton, The Hospital for Sick Children in Toronto and the IWK Health Centre in Halifax, has become an international initiative involving researchers in 14 North American cities.

"This is groundbreaking work that is pushing the frontier of what we know about the biological nature of autism, and why it emerges so early in life," Dr. Lonnie Zwaigenbaum of McMaster University says in a statement.

"Our hope is that it will lead to the development of new and earlier treatments that could make a huge difference for these children."

In the absence of biological markers to diagnose autism – something the blood-test research may change – clinicians have been forced to rely on behavioural checklists for children 18 months and older.

Noting the lack of an equal instrument for younger infants, Canadian researchers produced the Autism Observation Scale for Infants.

Led by Susan Bryson, Craig Chair in Autism Research at the IWK Health Centre/Dalhousie University, and co-lead investigator for the study, researchers developed the tool, which maps the development of infants as young as six months.

The scale looks for 16 specific autism risk indicators. Some of the risk behaviours include not smiling in reaction to others' smiles or not responding when one's name is called.

"The predictive power of these markers is remarkable," Dr. Zwaigenbaum says.

"We are finding that within this high-risk group of siblings, almost all of the children who are diagnosed with autism by age two years have seven or more of these markers by the time they are a year old."

The findings indicate that there are behaviours that distinguish siblings at six months of age from those who are later diagnosed with autism.

These behaviours include:

• passive temperament and decreased activity level at age six months, followed by extreme irritability
• a tendency to fixate on objects
• decreased social interaction
• lack of facial expression nearing 12 months of age

At one year of age, the same infants showed difficulty communicating. They used fewer gestures, and understood fewer phrases, the study reports.

The researchers also note that it is not yet know whether these risk markers indicate an early manifestation of the disorder, or whether they hamper the child's opportunity to learn, thus contributing to a pattern of growth that may later lead to autism.