Genetic Medicine

Is Genetic Testing Right for You?

You could uncover a condition that hasn’t yet caused any symptoms…

Genetic testing can save lives by alerting individuals to risk factors for diseases that may be hiding in their genes. But most patients are missing out on these benefits because the tests aren’t well-understood. Traditionally, genetic testing has been used to screen newborn babies for treatable conditions and by prospective parents concerned about passing on genetic diseases to their children.

What few people realize: There are now many tests that are useful for adults who may wonder about conditions, such as certain types of heart disease, cancer, Alzheimer’s disease or Parkinson’s disease, that tend to develop later in life. In fact, there are more than 1,000 genetic tests to detect the “variants” in genes (DNA) that can cause or complicate such health problems—before symptoms develop.

PREDICTIVE TESTING

This type of genetic testing (typically based on an analysis of blood or saliva) predicts your risk for a specific disease long before symptoms appear. A marked family history of the disease (in a first-degree relative such as a parent or sibling, for example) usually prompts a doctor to recommend the test. Predictive testing can be helpful for…

• Colon cancer. If you have a first-degree relative who had colon cancer before age 50, you may have the APC mutation, which causes familial adenomatous polyposis, a precursor to colon cancer. Or you may test positive for Lynch syndrome, a hereditary predisposition to colon cancer that carries a lifetime risk for the disease of 10% to 74%, depending on the specific gene and mutation. Lifetime colon cancer risk for the general population is about 5%.

Depending on the results of your test, you and your doctor may decide that you should…

Have a colonoscopy every year, not every 10 years, if you test positive for the APC mutation or Lynch syndrome…or have a total colectomy (removal of the colon) as a preventive measure.  

Get more frequent screening for ovarian and uterine cancer—risk for both cancers is also significantly increased in women with Lynch syndrome. You may also consider prophylactic surgery to remove the ovaries and/or uterus.

Receive a customized chemotherapeutic regimen proven to have greater efficacy in people with Lynch syndrome if you do develop colon cancer.

Heart disease. People whose first-degree relatives have had (at any age) certain cardiac conditions (see below) may be predisposed to sudden cardiac death or heart disease. Genetic testing is recommended for disorders including…

Hypertrophic cardiomyopathy, an inherited disease that causes thickening of the left ventricle, one of the four chambers of the heart…ventricular tachycardia, a faster-than-normal heartbeat that starts in the heart’s lower chambers…or atrial fibrillation, an irregular heartbeat caused by a misfiring of the heart’s electrical system. If testing reveals one of these conditions, your doctor will be able to treat you sooner.

Breast and ovarian cancers. If there is a history of breast or ovarian cancer in your family, with two or more relatives affected at a relatively young age (before age 50), ask your doctor if you should have a test for BRCA1 and BRCA2 genetic mutations.

An unexpected risk: These genetic mutations are also found in about 5% of patients with prostate and pancreatic cancer. Therefore, both men and women may want to consider the BRCA1 and BRCA2 test if these cancers have occurred in two or more of their family members before the age of 60.

GETTING TESTED

Among the issues for you and your doctor to deal with in the process of deciding to get a genetic test…

• Usefulness of the results. Deciding before the genetic test how you will use the results is an important part of the test process. For example, if Alzheimer’s disease runs in your family, you may decide to be tested for a genetic variant in the APOE gene that indicates an increased risk for the illness.

The dilemma: If the test results reveal you have the APOE variant, there is no medicine or surgery that can address your genetic risk. However, you may be more motivated to make lifestyle changes, such as eating a Mediterranean diet or walking regularly, since studies show these can lower the risk for Alzheimer’s. You might also change your long-term planning—such as moving closer to your family.

• Health insurance. In the APOE example above, it is likely that your insurer would not pay for this genetic test because the result would not affect your medical treatment.

Similarly, if you are concerned about breast cancer and want a test for BRCA1 and BRCA2, the insurance company may deny the request because the insurer may believe that your family history doesn’t warrant the testing.

Helpful: If the test is not covered, you may try to get authorization for it by asking your doctor to write a letter indicating that the testing is a medical necessity and providing the relevant supporting data.

Good news: The Genetic Information Nondiscrimination Act (GINA) of 2008 prohibits most group health insurers from denying insurance coverage or adjusting group premiums based on the genetic information of members of the group.

• Psychological repercussions. Before receiving a genetic test from your doctor, talk to a genetic counselor. The counselor can help determine if you need the test, provide psychological support when you receive results and also help determine whether or not family members should be informed about the results of your test, which could be meaningful for their own health. A genetic counselor can also help you through the maze of health insurance.

To find a genetic counselor: Ask your doctor for a referral or consult the National Society of Genetic Counselors.

Source: Robert Nussbaum, MD, chief medical officer at Invitae, a genetic information company based in San Francisco. He is the former director of the Cancer Risk Program at the Helen Diller Family Cancer Center, the Program in Cardiovascular Genetics and the Genomic Medicine Initiative, all at the University of California, San Francisco. Prior to those posts, he was chief of Genetic Disease Research at the National Institutes of Health. He is also the coauthor of more than 200 scientific publications in human genetics and coauthor of the textbook Genetics in Medicine.

Date: November 1, 2015

Publication: Bottom Line Health

See this post online at: https://bottomlineinc.com/health/genetic-medicine/is-genetic-testing-right-for-you