Health & Fitness

Genetic tests can unravel the mysteries of your DNA

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A patient came to Elizabeth Kearney with a dilemma: whether to go to medical school.

There were a lot of physicians in his family and he wanted to be a doctor, but medicine was not the only thing in his genes — one of his parents had Huntington's disease. The young man had a 50% chance of inheriting the degenerative brain disorder, which strikes in middle age, causing a loss of cognitive function, uncontrolled movements, emotional problems and, finally, an early death.

He took a genetic test and learned he had the abnormal gene.

"He wanted to go to medical school but that takes years, so he wanted to know how long he would last before getting symptoms," said Kearney, president of the National Society of Genetic Counselors. "He decided to open a sporting goods store instead because he wanted to get as much out of his life as he could before it was shortened by the disease."

In recent years, the field of genetics has expanded broadly, and Kearney's patient offers just one example of why you might want to know the mysteries that lie within your DNA.

Here are the basics if you are considering genetic testing.

What can these tests do?

Couples whose family tree branches carry conditions such as muscle disease, neurological problems and mental retardation can be tested to see if the issues are genetic and thus could be passed down to their children. Some ethnicities are more prone to certain diseases — sickle cell anemia in the case of African Americans and Latinos, for example, and Tay-Sachs disease in people of Eastern European Jewish descent).

A lot of patients request this type of testing before pregnancy, Kearney says. She talks with them about their background and pregnancy risks and counsels them regarding the available testing and the benefits and limitations of the tests.

All newborns are screened for birth defects at the hospital from blood obtained via a heel prick. The tests cover a panel of disorders, some genetic, that vary from state to state; some of the most common tests include ones for heart defects, spina bifida and Down syndrome. Positive results are followed up by a genetics team that notifies the parents.

Older children may also be tested for a variety of reasons. Infants born with a physical trait such as a cleft lip are sometimes tested to see if there is an underlying genetic explanation. This can help families figure out proper treatment and understand whether future siblings might be born with the same disease.

"Really for any child born with a physical birth defect, or who isn't meeting milestones of walking and crawling or language development at the right time … it is very reasonable to talk with a pediatrician and see if there is a genetic issue," Kearney says.

Increasingly, genetic tests are focused on adults to see if common chronic conditions such breast and colon cancer or heart disease might have strong genetic influences. These issues may be related to genetics if either multiple family members have been diagnosed with the same disease, or a relative has been diagnosed at a young age (meaning under 50).

What to expect

If you are interested in receiving genetic testing or counseling, there are a couple of ways to proceed. You can talk with a primary care physician, pediatrician or obstetrician to help facilitate the testing. Some doctors will perform the testing (typically by drawing a blood sample or taking a cheek swab) in their offices. Some will refer patients to genetics practices.

If you want to go directly to a genetics counselor, you can find local practitioners by visiting the National Society of Genetic Counselors (www.nsgc.org) and clicking on "Find a Counselor" on the left side of the Web page.

Michelle Fox, a genetics counselor and adjunct assistant professor of pediatrics at the David Geffen School of Medicine at UCLA, says she wishes everyone undergoing a genetic test "had 30 minutes to talk to a counselor before taking that test. They could learn what it's about, and the pros and cons."

It's important to make sure you are getting the right test depending on your medical condition and family history and the right information about the results, she says — in part because it can be expensive. Tests can cost from hundreds of dollars to $3,000 to analyze a gene, and insurance doesn't always pay the entire fee.

When you go in for testing and counseling, it is good to come prepared, Fox says. If children have developmental delays, make a record of their milestones. Compile a family history stretching back to the patient's grandparents, including information on any birth defects, special education (which could potentially indicate developmental delays), autism, unusual neurological issues such as seizures, sudden death and visual or early hearing loss, and anything else out of the ordinary.

If there is a history of a disease in the family, find out who was affected, exactly what they had (was it ovarian or cervical cancer, for example) and their age at the time of diagnosis and death, if applicable. If the family member's medical records are available, those are "gold," Fox says.

To help with this task, the Department of Health and Human Services offers a family portrait tool that can be stored online and printed to take to a counselor at http://www.hhs.gov/familyhistory/portrait/index.html.

Other considerations

People considering genetic testing should ideally have a good support system in place, Kearney says. She asks patients if they have family or friends nearby, and helps them find support groups that understand the issues they may encounter should they test positive or be diagnosed with an illness.

It's also important to understand what is being tested, what it can tell you and how to interpret the results, Kearney adds. The tests aren't infallible — a negative result may be deceptive. For instance, if you test negative as a carrier of cystic fibrosis or Tay-Sachs before getting pregnant, your child may still be born with the disease. The tests look only for certain common types of gene mutations and you may have one not detected by the test. Kearney says this is a very common occurrence.

Individual issues are factors, as well. Some people are information-driven and want to know their odds as they plan for the future; others may be happier not knowing, especially if the disease is incurable. You should consider how you would use the information and if it would be something you would want to share with family members, if it is relevant to them. All of this can be discussed with a genetics counselor.

Despite such complexities, Kearney says genetic tests are important tools that help patients such as her potential medical student make vital choices about their future.

"The benefits can be tremendous," she says.

health@latimes.com

Copyright © 2014, Los Angeles Times
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