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New genetic test 'three times better' at detecting autism

22 March 2010
Appeared in BioNews 550
New research into diagnostic genetic tests for autism spectrum disorders (ASDs) has revealed the effectiveness of a new test that is currently not used in the first line of diagnosis. The findings were published online last week in the journal Paediatrics.

The current genetic tests for ASD are G-banded karyotype, which looks at visible chromosome size, shape and number abnormalities, and fragile-X, which tests for a specific disease known to be a genetic cause of ASD. These are considered to be first-tier diagnostic approaches by the American Academy of Paediatrics. The new method, chromosomal microarray analysis (CMA), was developed in 2006 at the Children's Hospital Boston in the US and has been being evaluated ever since.
'CMA clearly detects more abnormalities than the other genetic tests that have been the standard of care for many years,' says Dr David Miller of the hospital's Division of Genetics and its Department of Laboratory Medicine, and co-author on the study.
'We think it should absolutely be a first-tier test for autism. It is already being used, but it is not being used in every patient all over the country uniformly,' he added.
Based on this research, experts including Dr Randi Hagerman, director of the MIND Institute at University of California, have recommended that ideally genetic testing, including CMA, should be done on all ASD patients.

The authors of this study, also from the Children's Hospital Boston, compared the three methods using a group of 933 patients with ASD. They found that G-banded karyotype testing identified genetic abnormalities in 19 of 852 patients (2.2 per cent) and fragile-X in 4 of 861 patients (0.4 per cent). CMA identified abnormal results in 59 of 848 patients (seven per cent), yielding a detection rate at least three times more effective than the others.

Co-author Dr Bai-Lin Wu, of the Harvard Medical School and director of the Genetics Diagnostic Lab at the hospital, says: 'from the number itself, seven per cent does not look like a large percentage. However, there are a lot of kids being diagnosed with autism, so it is seven per cent of a large of a very large number'. And since 15 per cent of ASD cases have a genetic cause, this is nearly half of the genetic cases.
Having a genetic diagnosis for a disease like ASD can help families and doctors confront the risks and possible treatments for the patient, as well as abolish any guilt the parents may harbour for their child's condition, and determine the risk of the parents having another child with autism in the future.

However, Dr Andy Shih, vice president for scientific affairs for Autism Speaks, which funds research on the disease, warned that the 'utility of this test in actual clinical settings is not clear', and has called for more research into the new test.

Autism is a complex disorder effecting a person's social interactions, and resulting in diminished language abilities and communications, as well as rigid and repetitive behaviours. According to the paper's authors, it affects around one in 1000 people; ASD, incorporating autism and its associated syndromes, affects six per 1000.
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Study Shows CMA Test Is More Accurate Than G-Banded Karyotype or Fragile X
Web MD |  15 March 2010
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