Potential genetic test to aid autism diagnosis

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 The tests were more likely to identify mutations in a subgroup of children with certain physical anomalies, making clinical examination an important way of selecting those children with autism spectrum disorder (ASD) who could benefit most from genetic testing.

"It is incontrovertible that precise diagnoses pave the way to better medical care, improved surveillance, better functional outcomes, and informed genetic counseling, often with the possibility of prenatal or preimplantation diagnosis," says an editorial in the same issue of the journal.

Stephen Scherer, PhD, of the Hospital for Sick Children in Toronto, Canada, and colleagues used the two newer technologies - chromosomal microarray analysis (CMA) and whole-exome sequencing (WES) - to determine the percentage of 258 unrelated children with ASD who possessed a genetic mutation that may contribute to their autistic features.

A molecular diagnosis from CMA was received by 24 (9.3%) of the children, and from WES by 8 of 95 (8.4%) of them. Among the children who underwent both CMA and WES testing, the estimated proportion with an identifiable genetic cause was 15.8%.

The proportion with a genetic mutation was much higher (37.5%) for children who had more complex ASD based on physical examination.

In the linked editorial, Dr. Judith Miles, of University of Missouri Health Care in Columbia, says:

"For ASD, as well as for other behaviorally defined disorders, the results [...] provide clear guidance."

Dr. Miles adds:

    "Foremost, the data indicate that physicians responsible for children with ASD should arrange access to a genetic evaluation using techniques that have the best chance of determining an etiologic diagnosis."

Parents interested in genetic testing

The authors conclude that their study gives a demonstration of genetic differences related to subgroups of ASD children based on clinical examination.

"Our data suggest that medical evaluation of ASD children may help identify populations more likely to achieve a molecular diagnosis with genetic testing," they note, adding:

"It seems likely that genetic testing of children with ASD will continue to increase. In a survey of parental interest in ASD genetic testing, 80% of parents indicated that they would want a sibling younger than 2 years tested to identify ASD-risk mutations even if the test could not confirm or rule out the diagnosis."

"For some children with positive genetic test results," they continue, "treatment plans targeting ASD-associated medical conditions can be offered."

The researchers conclude that if "replicated in additional populations, these findings may inform appropriate selection of molecular diagnostic testing for children affected by ASD."

The editorial points out that karyotyping - profiling the chromosomes - is much less informative than the new methods yet are tests for ASD recommended by geneticists.

Dr. Miles believes "it seems possible that it will not be too long before the evidence presented" by the study "will prompt a similar recommendation to include whole-exome DNA sequencing as a first-tier ASD test, if not for all ASD diagnoses, certainly for children with physical dysmorphology."