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Clinical Genetic Diagnosis

Standards for Clinical Genetic Testing for Autism Spectrum Disorders

The goal of this project was to study the possible genetic causes of autism spectrum disorders and determine what types of clinical genetic tests should be offered to individuals with an ASD.  The study revealed that chromosomal microarray analysis (CMA) had the highest detection rate among clinically available genetic tests for patients with autism spectrum disorders and should be part of the initial diagnostic evaluation of all patients with ASDs unless a genetic diagnosis has already been made.

The study was a collaborative effort between the Autism Consortium and Children's Hospital Boston and was led by Consortium members Bai-Lin Wu, David Miller, Kira Dies, and Yiping Shen.  The research team examined 933 families (children and parents) who received clinical genetic testing for a diagnosis of Autism Spectrum Disorder (ASD) between January 2006 and December 2008.  The researchers compared the findings from three clinical genetic tests: G-banded karyotype and fragile X testing, the current standard battery of genetic testing, and chromosomal microarray analysis, for which testing guidelines have not yet been established. Chromosomal microarray analysis is similar to a karyotype, but can find much smaller chromosomal deletions and duplications.

The results showed that chromosomal microarray analysis identified more genetic abnormalities associated with autism than the standard testing methods combined:

  • Standard testing method G-banded karyotype testing yielded abnormal results in 19/852 patients (2.23%)
  • Standard testing method Fragile X testing results were abnormal in 4/861 patients (0.46%)
  • In contrast, chromosomal microarray analysis (CMA) identified deletions or duplications in 154/848 (18.2%) patients and 59/848 (7.0%) were clearly abnormal.
  • As a result, chromosomal microarray was better than a karyotype for all but a small number of patients with balanced rearrangements, and those were not necessarily a cause of ASD.

To read more about the research that was publised in the journal Pediatrics in April 2010 please see our Press Release page