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.
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.
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.