New Genetic Autism Test Beats Older Tests
Study Shows CMA Test Is More Accurate Than G-Banded Karyotype or Fragile X
WebMD News Archive
March 15, 2010 -- A new genetic test for autism, known as chromosomal
microarray analysis (CMA), finds more genetic abnormalities than two older
tests, a study shows.
''CMA is much better than karyotyping or fragile X testing at detection --
it's at least three times better," Bai-Lin Wu, PhD, medical director of
the genetics diagnostic laboratory at Children's Hospital, Boston, and a study
co-researcher, tells WebMD.
While the other two tests are now standard practice, Wu and his colleagues
say the new test should also be part of the initial diagnostic evaluation of
patients when a clinical diagnosis of autism or autism spectrum disorder has
been made or is suspected.
The study results are published online in Pediatrics.
Autism, a complex disorder, involves impairments in social interaction as
well as deficits in language and communication along with rigid and repetitive
behaviors. It affects about one person per 1,000, the researchers write; autism
spectrum disorder (ASD) affects six per 1,000.
Comparing CMA With Other Tests
The researchers compared the results of the three tests in more than 800
patients. Among the findings:
- The standard genetic test known as G-banded karyotype testing found
abnormal results in 19 of 852 patients, or about 2%.
- The fragile X testing found abnormalities in four of 861patients, or about
0.5%. (Fragile X syndrome is a condition associated with autism.)
- The CMA test found abnormalities in 154 of 848 patients, or about 18%; 59
of these, or about 7%, were associated with possible or known genetic
''Karyotype testing is looking for changes visible by the microscope," Wu, a
clinical molecular geneticist, tells WebMD. "CMA is looking at the molecular
Wu and co-researcher Yiping Shen, PhD, assistant director of the genetics
diagnostic laboratory, compare karyotype testing to a map that can detect a
highway that's missing in a state, and CMA testing to a map that can detect
individual highway exits that are missing.
In the study, Shen and his colleagues say that CMA ''should be considered as
part of the initial diagnostic evaluation of patients with ASD."