Two new autism detection methods are promising to offer clinicians objective diagnostic tools that are not based on subjective behavioral assessments. Both systems are in early stages of clinical verification, so not quite ready for prime time, but they enter an increasingly busy field of research into objective autism biomarkers, suggesting it shouldn't be too long before parents have a variety of new tests to catch the condition at its earliest stage.
"Autism is hard to screen for in children, when the first signs are present," explains Caroline Robertson, director of the Dartmouth Autism Research Initiative. "A trained clinician may be able to detect autism at 18-months or even younger; yet, the average age of a diagnosis of autism in the U.S. is about four years old."
The Dartmouth research is based on the previously studied observation that autistic brains process visual information differently from normal brains. The theory is called binocular rivalry, and it stems from the way a human brain toggles between right and left eye image processing when confronted with two separate pictures simultaneously.
Prior research has established slower rates of binocular rivalry in autistic individuals, so the new study set out to develop a simple test to measure this process. Using just one single EEG electrode and a computer screen presenting certain visual imagery, it was discovered the researchers could effectively track an individual's rate of binocular rivalry.
The technique was tested on a small sample size of 18 autistic adults, and 19 age- and IQ-matched control subjects. The method effectively separated the autistic subjects from the controls with 87 percent accuracy. But perhaps even more interesting was the finding that alongside simple binary positive or negative predictions, the rate of binocular rivalry could effectively predict an individual's autism severity, meaning the slower the rate of binocular rivalry, the higher the severity of autism symptoms. This is potentially an even more valuable metric for clinicians, as autism is obviously a disorder with a wide spectrum of manifestations.
"This visual test may be a non-verbal marker of autism in adults," says Robertson. "Our next steps are to learn whether this test could potentially be used to detect autism in pre-verbal children and non-verbal adults and develop it into a screening tool for the condition."
Another new autism diagnostic tool comes from Australian optometry researcher Paul Constable, who has been working for over a decade to identify biomarkers of autism that can be easily detected in the eye. Constable's work, still under peer review ahead of journal publication, suggests a small hand-held device can quickly scan a child's eye and detect whether the child is autistic.
"The retina is an extension of the brain, made of neural tissue and connected to the brain by the optic nerve, so it was an ideal place to look," explains Constable. "We found a pattern of subtle electrical signals in the retina that are different in children on the autism spectrum, which relates to differences in their brain development."
The preliminary efficacy study of the device looked at 89 autistic subjects and 87 healthy controls. All subjects in this initial trial were aged between five and 21, so questions still remain as to whether the device can accurately identity autistic individuals at younger ages. Work is currently underway, in collaboration with Yale University and University College London, to verify the test on very young children.
Both new diagnostic methods are still a few years away from broad clinical application, however, they signal a growing understanding into what causes autism and how it can be objectively identified. Other exciting innovative detection methods currently under investigation include facial detection systems, MRI scans, blood tests, urine tests, saliva tests, EEG readings, and even a smartphone app.
"Very early diagnosis means not only can children receive important interventions, but families are empowered to get the necessary supports in place, come to terms with the diagnosis, and make informed decisions," says Constable on the importance of an objective diagnostic tool for detecting autism.
The binocular rivalry research has been published in the journal Current Biology.
Sources: Flinders University, Dartmouth