College of American Pathologists
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  "No cookbook approach"





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"If DNA doesn’t add up, array CGH steps in"
DNA Samples (PDF document 1,431 K)

September 2005
Feature Story

What does array CGH look like to a practicing medical geneticist?

"From a clinical geneticist’s perspective, microarray analysis allows us to identify children with subtle chromosomal abnormalities that are not detected by available standard techniques—karyotyping or FISH analysis," says Mira Irons, MD, FACMG, interim chief in the Division of Genetics at Children’s Hospital, Boston, who sends occasional samples for array CGH. Among patients seen by a clinical geneticist, approximately 40 percent to 50 percent don’t have a diagnosis. No chromosomal abnormality or metabolic condition can be identified and no syndrome can be diagnosed based on how the child looks. In these patients, Dr. Irons says, array CGH provides an additional tool. She estimates that it can identify an underlying chromosomal abnormality in a few percent of kids being sent to a geneticist for evaluation.

"In my own personal practice, having microarray analysis has allowed me to diagnose a few kids that I have been following with mental retardation of unknown etiology or multiple congenital anomalies of unknown etiology or growth retardation," Dr. Irons says.

She suggests that, as array CGH covers larger sections of the genome, it may replace standard karyotyping. "Clearly it is not there yet," she says. "Doing initial karyotyping is still a geneticist’s first-line test. Depending on the clinical presentation, I might then go to FISH or microarray."

As for cost, she considers array CGH to be like any other expensive test. "You have to weigh the cost of doing the test against the chance of getting a diagnosis and its benefits," she says. The cost of array CGH must also be balanced against the cost of doing many FISH probes or many metabolic tests. "There is no cookbook approach to evaluating children with mental retardation or congenital anomalies or growth problems," Dr. Irons says. "You have to determine the best testing path for that child."

William Check, PhD