Advanced gene test better at detecting autism

The commonly used standard genetic tests often fail in spot the genes responsible for causing autism.

But the new test known as chromosomal microarray analysis (CMA) is more advanced and sensitive as it searches the entire genome for minimal chromosomal changes, the researchers stated.

They are hopeful that the test may enable early intervention for autism diagnosis at a younger age.

Autism is a neurological disorder characterized by impaired social interaction and communication, restricted and repetitive behavior. These signs all begin before a child is three years old.

Details of the study
To come up with this finding, a research team from the Children's Hospital Boston and the Boston-based Autism Consortium focused on 933 families (children and parents) who were diagnosed with Autism Spectrum Disorder (ASD).

All these patients had received clinical genetic testing for ASD between January 2006 and December 2008.

For the study, the researchers compared the efficacy of three tests--G-banded karyotype and fragile X testing, the current standard battery of genetic testing, and chromosomal microarray analysis on these patients.

According to experts, CMA is similar to karyotype but it can detect much smaller chromosomal deletions and duplications unlike the standard genetic tests.

Results of the study
On analysis, they found that the karyotype test was able to detect autism related genetic abnormalities in 2.23 percent of the patients, standard tests spotted the abnormalities in just 0.46 percent of the patients, while CMA faired the best with a rate of 7.3 percent.

Although seven percent isn’t a large number but compared to the first-tier-tests for autism as states the American Academy of Pediatrics, CMA worked three times more effectively than the standard tests, the researchers noted.

"This is the largest study of clinical genetic testing for patients with autism spectrum disorders, and the results clearly show that chromosomal microarray analysis detects genetic abnormalities leading to ASD more often than a standard karyotype and fragile X testing," said David Miller, assistant director of the DNA Diagnostic Laboratory at Children's.

"What we showed here is what happens when you order all three of these tests up front. You end up getting more information from ordering the microarray test than from both of the two other tests combined," Miller said.

The study and its findings have been published in the April issue of the Journal Pediatrics.