By Laura Blue
Diagnosing autism currently requires hours of observation by clinicians and a far from objective series of behavioral measures, but improvements in genetic testing could make the process more efficient.
In a study published in the journal PLOS ONE, researchers from Children’s Hospital Boston describe a new experimental test to detect the developmental disorder, based on the differences in gene expression between kids with autism spectrum disorder (ASD) and those without the condition. The blood-based test appears to predict autism relatively accurately, at least among boys, and has already been licensed to a company, SynapDx, for commercial development. In an email statement to TIME, a spokeswoman for SynapDx said the company plans to start clinical trials of the new test in early 2013.
The new blood test for autism is intriguing, researchers say, because it seems to be at least as effective as any other genetic test for autism that doctors currently use. Scientists believe that autism has some genetic basis, based on genes that have been associated with the disorder, and the fact that the condition seems to run in families. “A week does not go by where you don’t hear about a genetic mutation that has been linked to autism in at least a few families,” says Isaac Kohane, a pediatric endocrinologist and computer scientist at Children’s Hospital Boston, and the senior study author on the new article in PLOS ONE. Kohane is a scientific adviser for SynapDx, but says he does not own any stock in the company.
But autism is a complex condition, he says, with many possible genetic determinants. And the precise genetic mechanism, or more likely mechanisms, are still poorly understood. But to get a better idea of which genetic changes might be most relevant to the disease, Kohane and his colleagues compared 66 patients with ASDs and 33 similar patients who were not affected by the disorder. Because they couldn’t analyze the participants’ brain tissue, they relied on their blood as a proxy for revealing any differences. And indeed, they found certain markers in the blood of autistic participants that did not appear in those without the disorder. They traced these to 489 genes and narrowed that list down to 55 genes that could predict autism in about two-thirds of those with the disease.
“There are a lot of different mutations involved, and a lot of different pathways that seem to be involved in autism,” Kohane says. Those genetic pathways included some known to be related to learning, and some linked to immune function. “The fact that not all kids had both, and some kids would be more abnormal in immunological pathways and others would be more abnormal in [another pathway] spoke, I think, to the genuine heterogeneity of the disease,” Kohane says.
“In that respect, autism is beginning to look a lot like what the cancer biologists are telling us about breast cancer, or lung cancer,” he says. “There may be hundreds of different molecularly defined cancers, which each have their own specific optimal treatment.” Similarly, autism spectrum disorders, too, may have diverse genetic roots, and appear clinically in slightly different ways from one patient to another.
Today, 1 in 88 kids suffers from an autism spectrum disorder, and prevalence has soared over the last 30 years, although it’s not clear why. Diagnosing the disease early is important because it allows children to take advantage of behavioral intervention programs that can lead to higher IQ scores and improvements in language. Kohane says the blood test could identify those at risk of autism well before symptoms appear around age 2, and help these children access potentially beneficial therapies.
The test, however, is still in early stages of development. Kohane says that its accuracy (at around 70% in a high-prevalence, predominantly male sample) is high enough to be clinically useful among kids with a suspected developmental disorder. But he stresses that the test as it stands still generates too many false positives, or people mistakenly identified with the condition when in fact they don’t have it, for the test to be used as an autism screening tool among all children. If the current results are confirmed, that may take a few more years.