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Genetic Testing: Knowledge Is Power, but Is Ignorance Bliss?

The science of genetics holds the promise of someday wiping out a whole range of diseases from cancer to diabetes and heart disease, but it can also help us today. Our health correspondent Dr. Emily Senay explains.

If you have a family with a history of disease and wonder what or if there's anything you can do to identify the genetic causes and stop the disease before it develops, nowadays you can ask a doctor known as a genetic counselor.

Sisters Dana Crawford and Cecelia Barr are worried about the high incidence of early onset heart disease in their family. Their father had his first of three heart attacks when he was 38.

"It was my birthday. I turned 27 and my dad reminded me that I was only 10 years away from how old he was when he had his first heart attack--so that's not comforting," says Cecelia.

The worried sisters sought the advice of genetic counselor Dr. Maren Scheuner of Cedars-Sinai Medical Center in Los Angeles. "There are some common genetic factors that we are going to be measuring in your blood today to determine if that might be playing a role in the risk for coronary artery disease and heart attack in your family," says Scheuner. "Once we identify those risk factors, then we can discuss with them ways to modify those risk factors either through diet, exercise, other lifestyle changes, [or] using medications or vitamin therapy."

Blood samples are taken and tested for genes related to blood clotting as well as for other biochemical markers believed to be hereditary, like high cholesterol. If a genetic flaw is discovered, it doesn't necessarily mean that the disease will develop, but it gives doctors an obvious target to aim at to help prevent the disease.

"Understanding the specific genetic predisposition for that condition, whether it be heart disease, diabetes, or cancer--we'll be able to target treatments to medications that are specific to a genetic risk," says Scheuner.

Luckily the tests all turned out normal with no suspect genes discovered. For Cecelia, the results are a relief.

"I can't see myself going through what my dad went through, and not only that, my mom had to go through it with him," says Cecelia. "So to prevent that is really important to us."

Even though their tests were okay, they'll need to keep vigilant about diet and exercise and keep repeating the tests to make sure they stay within normal ranges. As we learn more about the genetic links to heart disease, the tests will tell us more. We already know about genetic links to high blood pressure and blood clotting, and researchers are working on figuring out which cholesterol-lowering medications will work better for different genetic profiles. So heart disease is one area where knowing your genetic makeup will really make a difference in the near future.

Is it useful to know your genetic susceptibility to every disease?

It depends on the disease and it depends on whether there's a treatment for i. Prenatal genetic screening is already useful in predicting birth defects and some childhood diseases. With some adult diseases like heart disease or breast cancer the treatments and early intervention are highly effective, so it's worth knowing your genetic makeup and exploring your options. But for diseases that we don't know how to treat or prevent effectively like Huntington's disease or Alzheimer's, it's not going to help if you know you have the gene, especially since having the gene doesn't necessarily mean you're going to get the disease.

Can your primary care doctor give you this type of counseling?

Many of the basic blood tests are available and are part of a general physical, but most primary care physicians don't have the time to do this type of thorough hereditary evaluation including the family tree evaluation and genetic tests.
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