Genetic Testing: Is It For You?
Many hail genomics, the study of DNA sequencing and genetic mapping, as the medicine of tomorrow; personalized medicine based on an individual’s specific DNA.
According to the National Institutes of Health, there are over 2,000 genetic tests available which, more than ever before, can provide you and your health care practitioner with a roadmap for your health and ways to manage it. The information gained from these tests can determine diseases to which you may be predisposed; what medicines work for you and which do not; and what conditions you may pass onto your children, to name a few.
“I’ve been a student of medicine for three decades and I’ve never seen any time as exciting and as extraordinary as this one,” says Eric Topol, M.D. Cardiologist, Chief Academic Officer of Scripps Health, and Professor of Genomics at The Scripps Research Institute. “A patient’s emerging and unprecedented access to his or her important health information is reshaping medicine.”
More and more medical professionals are offering genetic testing, and many websites are even promoting DNA analysis for as low as $99. “Any genetic testing that provides insight to your DNA coding will be fun and interesting,” says Dan Olesnicky of Executive Urgent Care in Indian Wells which provides 15 different genetic tests. “It’s like reading your own owner’s manual.” But Olesnicky and others advise caution to ensure that the lab used is reputable and that results are comprehensive and accurate. In addition, there is the chance that the information provided may affect you and your family members negatively, so it is good to have a medical professional on hand to review and discuss results.
What Are the Primary Reasons for Genetic Testing?
Pharmacogenetics. One of the fastest growing reasons is to determine if the medications you are taking – or need – work for you based on your body’s ability to metabolize them effectively. This information enables your doctor to prescribe proper medications and dosages. The most common tests are for cardiac and pain medications, but testing is also available for others including common psychiatric and cancer drugs.
In 2010, the Food and Drug Administration placed a Box Warning —its most severe safety advisory— on Plavix (generic name clopidogrel), the second biggest selling drug after cholesterol-lowering Lipitor. Approximately 3 million prescriptions are written monthly for this blood thinner to prevent clots in patients with advanced cardiovascular disease. The label warns that the product may not work for everyone. Indeed, up to 30% of those prescribed may have a mild genetic variation that could possibly affect response, increasing a patient’s risk for a potentially life-threatening heart attack.1 Treatment options for these populations include increased dosages of Plavix or another brand prescription.
As a result, leading medical institutions such as Scripps Clinic in San Diego and Vanderbilt University Medical Center are embracing genetic testing for cardiac patients. Scripps offers the option to patients and Vanderbilt automatically tests all those who undergo cardiac catheterization — approximately 4,000 patients per year.2
Many common pain medications require activation by an enzyme called CYP2D6 to become effective. At the 23rd Annual Meeting of the American Academy of Pain Medicine, a presentation on the clinical effect of genotyping chronic pain stated that approximately one half of prescribed patients have genes that alter the function of this enzyme. Testing allows for alteration of dosage regimens to compensate for altered metabolism, thereby optimizing the safety and efficacy of these analgesics.
Predisposition to disease. If you have a family history of a genetic condition, undergoing genetic testing before you have symptoms may show if you are at risk of developing that condition. This is the testing put in the spotlight recently by Angelina Jolie who tested positive for the BRCA1 gene mutation increasing her risk of breast cancer to 87% and ovarian cancer to 50%. She used this information to make choices for herself and her family and decided to have both her breast tissue and ovaries removed.
Since her announcement, requests for testing have increased significantly across the country. Time Magazine’s recent cover story “The Angelina Effect” discussed how her celebrity will significantly change the way genetic testing is viewed. “We have seen the number of genetic test requests double – maybe even triple,” says Kris Kalla, board-certified genetic counselor for Eisenhower Medical Center who specializes in cancer risk assessment. But a large portion of those people aren’t appropriate candidates. For hereditary cancers, Kalla notes, a family history is essential and some of the qualifying factors include: 1) early age of onset; 2) rare cases like male breast cancer, 3) multiple generations from one side of the family affected with certain constellations of cancer such as breast and ovarian or colon and uterine; and 4) if there are three or more relatives on the same side of the family with later onset cancers associated with a known hereditary cancer syndrome.
Qualified patients often are those who grow up with the fear of getting cancer because they have seen so many people in their families succumb (as in the case with Jolie). “If they test positive for something, we spend a lot of time counseling them and reminding them that they don’t have cancer at that time. It takes a while to digest.” Counselors are available to patients as needed and set up meetings with others who have that same hereditary syndrome. “We really try to be comprehensive not only in the science and medical aspect, but also in the psychosocial sense.” They also make sure patients get prompt follow up as an essential part of testing. “We don’t just drop the bomb on someone and let them diffuse it. That is a big part of our job and rather unique.”
The fact that genetic counseling is a field within itself supports the fact that it may be important to work with a medical professional when considering genetic testing. “We only test for things upon which we can offer solutions, such as early screening and surgery to reduce the risk,” states Kalla. Olesnicky agrees adding that they offer genetic testing only when appropriate.
Diagnostic testing. If you have symptoms of a disease that may be caused by genetic alterations, genetic testing can reveal if you have the suspected disorder. Examples include adult polycystic kidney disease, iron overload (hemochromatosis) and Charcot-Marie-Tooth disease.3
Carrier testing. If you or your partner has a family history of a genetic disorder, such as sickle cell anemia or cystic fibrosis, you may choose to have genetic testing before you have children. This type of genetic testing may also be useful if you are in an ethnic group that has a high risk of a particular genetic disorder. Genetic testing can determine if you carry a copy of an altered gene that would put a child at risk of developing the disorder.3
Prenatal and newborn testing. If you are pregnant, tests are available that can detect some types of abnormalities in your fetus’s genes. Spina bifida and Down syndrome are two genetic disorders that are often screened for as part of prenatal genetic testing. Newborn screening is the most common type of genetic testing. In the US, all states require that newborns be tested for certain gene abnormalities that cause specific conditions. This type of genetic testing is important because if results show there’s a disorder such as congenital hypothyroidism or phenylketonuria (PKU), care and treatment can begin right away.3
Is Everyone Ready for This New Science?
In a survey of the effect of genetic testing on medicine, Topol notes that of 10,000 doctors, 90% felt they were not up to speed and [do not yet] have the proper knowledge to use genomics in their daily practice. The field of genetic testing counselors is growing and as Kalla notes, there is so much new information on the subject that counselors often specialize just to keep up with the literature and category growth.
Topol adds that the patient perspective is quite different. “We studied and published on thousands of people who got genome-wide scans and showed that people were perfectly comfortable when they got that information—there was no increased anxiety or depression.” He says one-fourth of those studied shared the testing with their doctors, which led to better understanding of which tests to do and medicines to use. (Kalla notes that those studied were general population and not in the high risk category for disease.) “There’s a knowledge base we have to remedy,” he concludes, “because pretty soon the patients are going to know more about their own genomics than many doctors know about genomics overall.”
If you are interested in genetic testing, research your family history and speak with your health care practitioner or a qualified genetic counselor to determine if genetic testing is right for you.
References: 1) [03-12-2010] The U.S. Food and Drug Administration.Plavix Box Warning; 2) http://www.genomeweb.com/dxpgx/vanderbilt-medical-center-initiates-plavix-pgx-testing-all-cardiac-catheterizati; 3) http://www.mayoclinic.com/health/genetic-testing/MY00370/DSECTION=why-its-done
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