A Better Test for Finding Autism Genes?

A screening called CMA may help parents and researchers learn more about autism.

ByABC News
March 14, 2010, 5:30 PM

March 15, 2010— -- A genetic test for autism currently classified as a secondary approach may be able to pick out the underlying causes for the condition at a rate more than three times that of a screening considered to be a first-tier test, according to a new study published in the journal Pediatrics today by the Autism Consortium and Children's Hospital Boston.

Researchers launched the study to compare the newer screening, called chromosomal microarray analysis (CMA), against the tests that the American Academy of Pediatrics currently considers to be first-tier approaches -- G-banded karyotype and fragile X testing. They said they hope the new research will help the test achieve first-line status when it comes to determining the genetic reasons behind autism spectrum disorders.

The CMA test was developed at Children's Hospital Boston in 2006 and has been evaluated over the past few years.

"We think it should absolutely be a first-tier test for autism," said study co-author Dr. David Miller, assistant director of the DNA Diagnostic Laboratory at Boston Children's Hospital. "It is already being used, but it is not being used in every patient all over the country uniformly."

Study co-author Bai-Lin Wu of Harvard Medical School in Boston said CMA allows doctors to find the underlying genetic cause of 7 percent of autism cases.

"From the number itself, 7 percent does not look like a large percentage," Wu said. "However, there are a lot of kids being diagnosed with autism, so it is 7 percent of a very large number."

Specifically, Wu explained, there are about 4 million births every year in the United States. Current statistics from the U.S. Centers for Disease Control and Prevention put the rate of autism spectrum disorders in American kids at slightly less than 1 percent. This would mean that about 40,000 per year would be expected to have autism spectrum disorders.

Wu said the tests currently used as a first-tier test for autism may only detect 2 percent of the genetic abnormalities that could be behind the development of autism -- meaning that using these tests, it may only be possible to identify genetic causes for about 800 of these children. Linking an additional 5 percent of these cases to a genetic cause would mean an explanation for 2,000 more cases of autism each year.