News Release: Research , School of Medicine

Sep. 27,  2010

American College of Medical Genetics Recommends Chromosomal Microarray as New Practice Guideline

First-line diagnostic test for developmental/intellectual disabilities or birth defects was advocated by Emory-led international consortium

The American College of Medical Genetics (ACMG) has just released a major new Practice Guideline that recommends chromosomal microarray (CMA) as the first-line genetic test for all children with autism spectrum disorders and other developmental/intellectual disabilities or birth defects.

This updated guideline was largely influenced by an international genetics consortium led by David Ledbetter, PhD, Woodruff professor and director of the Division of Medical Genetics at Emory University School of Medicine, and Christa Lese Martin, PhD, Emory associate professor of human genetics.


Video featuring David Ledbetter and Christa Lese Martin

In May 2010, the International Standard Cytogenomic Array consortium (ISCA) issued a consensus statement recommending CMA as the new standard practice for genetic evaluation of children with unexplained developmental delay, autism or birth defects. The statement and a related research review were published in the May 14, 2010 issue of the American Journal of Human Genetics.

The ISCA is a group of clinical genetics laboratories and genomics experts focused on standardizing the collection of cytogenetic data. Cytogenetics is the study of the chromosomes within cells and chromosomal abnormalities.

“CMA is a tremendous improvement in diagnostic testing for these disorders and gives us a much better ability to counsel parents about their child’s developmental disability or birth defects,” says Ledbetter. “We are extremely proud that this project, initiated by our group at Emory and a very strong and committed team, has resulted in a major change in medical practice in a very short time frame and helped set the new standard of care for this group of patients.”

The ISCA Consortium made its recommendation after review of all published data by a large panel of experts in the field. The new ACMG Practice Guidelines specifically refer to the ISCA Consortium effort to establish a “standardized, universal system of reporting and cataloguing CMA results, both pathologic and benign, in order to provide the clinician with the most accurate and up-to-date information.”

“CMA is a commonly ordered test,” notes Ledbetter, “and the ACMG put it on a fast track for recommendation as standard practice. The test has become widely available and is now offered by multiple laboratories, thus there should be no problem with access.”

Ledbetter is particularly pleased that the recommendation includes autism spectrum disorders. “The autism community is less aware of clinical genetic testing than they should be, and most patients are seen only by psychologists and behavioral counselors. We need to educate parents that five to 10 percent of the time there is a specific genetic cause of autism that may have implications for these children, their parents and other family members,” he says.

Children with unexplained developmental delay/intellectual disability, autism spectrum disorders and multiple congenital anomalies account for the largest proportion of genetic testing because of the high prevalence in the population. Development delay/intellectual disability is present in about three percent of the population, and autism spectrum disorders affect approximately one in 110 people.

Previous guidelines had recommended testing with G-banded kayotyping, a type of chromosomal testing first developed in the early 1970s. CMA is a more detailed and accurate view of chromosomal abnormalities that examines a patient’s genome for detection of gains or losses of genetic material (known as copy number variation) that are too small to be detectable by G-banded studies.

The new recommendation is available on the ACMG website within “Practice Guidelines.” 

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The Robert W. Woodruff Health Sciences Center of Emory University is an academic health science and service center focused on missions of teaching, research, health care and public service.

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