The blood test in action. Louis Kunkel, PhD, right, and Hal Schneider, left, watch as the gene expression profiles of patients suspected to have autism are analyzed.
by Michelle Pflumm, PhD
Autism spectrum disorders (ASDs) can be a challenge to diagnose. A definitive diagnosis generally requires careful assessment on a series of performance tasks in a specialized clinic. Now, researchers at Boston Children's Hospital have developed a potential blood test that can be performed in a standard diagnostic laboratory and appears to identify ASDs with 85 percent accuracy.
Using microarrays to analyze patterns of gene activity in blood samples from 258 patients and 158 people without ASDs, Louis Kunkel, PhD, director of the Genomics program at Children's, and Isaac Kohane, MD, PhD, director of the Informatics program, have identified a genetic "signature" that consists of 245 genes uniquely switched on or off in people with ASDs.
"The signature we obtained supports the hypothesis that a number of mutations,
rather than a single mutation,are responsible for ASDs," says Kohane
Kunkel and Kohane hope that a test based on this signature would become a first-line diagnostic tool for ASDs. And, as they recruit more study subjects, they also hope to identify genetic signatures that discriminate between classic autism, Asperger's syndrome and unspecified pervasive developmental disorders (PDD-NOS).
"We are now looking at the whole autism spectrum because our numbers are small," says Kunkel. "What we want to do--once we have large enough numbers--is to start to subclassify those with ASDs."
The next big question is whether or not these differences in gene expression can be detected early enough to identify children at high risk before they show outward signs of ASDs. The earlier autism is detected, the earlier intervention can begin and the better the outcome.
In collaboration with Charles Nelson, PhD, research director of the Developmental Medicine Center, the Kunkel and Kohane team will look at gene expression signatures in infants who are at greater risk for ASDs because they have an affected brother or sister. Those with the suspect genetic expression signature will be followed over time to see how reliably it predicts disease.
"If you can get the assays down so that they are inexpensive and widely available," says Nelson, "then you can screen every newborn like you do with phenylketonuria."