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Having a parent with Huntington's disease gives you a 50 percent chance of inheriting the condition yourself. "I wasn't ready to know [my risk], but I was ready to stop destroying myself over it," says Rick, adding that getting tested was the scariest thing he's ever done. Rick's brother has been tested—he's still waiting for the results—but his sister hasn't decided yet if she wants to be tested.
Scientific advances over the last 10 to 20 years are changing the ways we predict inherited disease. No need to consult a psychic or crystal ball anymore—many hospitals and clinics now have the tools to predict genetic diseases such as Alzheimer's, sickle-cell disease and several cancers.
Equal parts frightening and enlightening, genetic screening is just beginning to gain speed, and more people are taking the plunge, for better or for worse. Just last year, Angelina Jolie publicly revealed that she carried an inherited breast cancer gene and had undergone a preventive radical mastectomy as a result. But would you want to know what your future holds? And what would you do if the big reveal turned out to be more death sentence than welcome sigh of relief?
How your DNA is formed
In order to understand how genetic testing works, here's a simple DNA refresher course. It's estimated that every person is composed of approximately 10 trillion cells. Each human cell contains 46 chromosomes organized into 23 pairs. Half of your chromosomes come from your mother, half from your father. Housed inside each chromosome are long, spiral strings of genetic material called deoxyribonucleic acid (DNA). Think of a twisted ladder and you've got a pretty good image of what DNA looks like under a high-powered microscope.
DNA contains genetic "instructions" for your cells to make your body grow and function. DNA tells your cells how to react to the foods you eat and the germs that cross your path, and even how to deal with aging. Certain segments of your DNA are called genes—they produce proteins responsible for your individual traits, such as eye, skin and hair colour. They also produce enzymes that dictate the chemical reactions inside your body. Wrap all this DNA material into one parcel and you've got what scientists refer to as a "genome." Your genome and that of your best friend, coworker and sister are extremely similar. The genomes of any two people—even unrelated people—are more than 99 percent the same.
But we all have genomic differences—unique bits of code that result in, say, curly hair or straight hair. Few of these variants have any bearing on your health, but sometimes a specific gene can be missing, or in the wrong place, or produce damaged proteins, creating a genetic mutation that can make an individual more susceptible to certain conditions.
Sometimes these mutations are passed down from generation to generation. Angelina Jolie's mother, Marcheline Bertrand, carried a mutated BRCA1 gene for breast, ovarian and fallopian tube cancer. In 2007, at the age of 56, Bertrand died of ovarian cancer. Jolie underwent screening for this gene and, sure enough, discovered that she carried the same mutation.
Many medical experts believe that Jolie played a significant role in raising public awareness of genetic testing. "When someone like Angelina Jolie, who is known worldwide, talks about her experience, it becomes more real to people," says Tina Babineau Sturk, a genetic counsellor and manager of the Maritime Medical Genetics Service at the IWK Health Centre in Halifax. "You might relate if you have a similar history, and [you may begin to] wonder if there's anything you need to think about."
The genetic screening process
According to William Foulkes, a professor in the departments of human genetics, oncology and medicine at McGill University, genetic screening isn't something most Canadians should worry about.
"Most people won't currently benefit from genetic testing because they don't carry genes for which a disease risk has been established," he says. But without testing, how can you know if you're one of the unlucky few? If you have one or more close family members (a sibling, parent, child, grandparent, aunt or uncle) with a particular disease, you could be at risk.
For Rick Adler, the diagnoses of both his grandmother and father provided proof that he would be a prime candidate for testing. Criteria for screening vary from province to province, but a family history of a specific disease will generally gain you access, and your provincial health plan should cover the cost.
If your doctor feels you might have an inherited risk, you will be referred to a hospital's genetic clinic. Before any DNA samples are taken, you'll meet with a genetic counsellor to discuss your situation, the pros and cons of unlocking this sensitive information, and the possible results.
Obtaining a genetic sample for testing is easy and relatively painfree—a blood test will provide sufficient DNA. Sometimes, if people are deathly afraid of needles, saliva can be used. "But that method is less common, because laboratories prefer to work with blood," says Babineau Sturk.
In most cases, the DNA is amplified and then analyzed for mutations within specific genes. If there are mutations, the person could be at higher risk of a disease or be a carrier (meaning they likely won't develop the disease themselves but can pass it on to their children). Results typically take several weeks to come in, after which you'll meet again with your counsellor to discuss the findings.
Pros and cons of genetic testing
There are pros and cons to genetic testing. When individuals receive an all-clear, the sense of relief can be overpowering. If the test comes back positive, individuals can look to preventive strategies and early treatment options. Carriers of BRCA1 and 2 fall into this group. They can take a wait-and-see approach and commit to regular testing, such as mammograms and MRIs, or they can undergo a preventive mastectomy.
But not everyone gets the opportunity to be proactive. Carriers of the Huntington's disease gene, for example, face a grim future. "It's a disease that is almost certain to be fatal, and there is no current effective treatment," says Foulkes. If you discover that you carry this gene, it can unleash a tremendous amount of worry, and maybe even despair.
There are also ethical quagmires to discovering what lurks in your genes. Family relations can become strained if loved ones would rather remain in the dark. Alternatively, when an entire family is tested, anything less than across-the-board good news can prove troubling.
"If a family goes through testing and one person is found not to have the mutation when the others have it, that person may suffer from survivor's guilt," says Babineau Sturk. Insurance coverage can also be jeopardized by genetic testing. "If you know your genetic information, you can't hide it. Once the result is in your medical file, you can't remove it," says Babineau Sturk. Consequently, you might be refused life insurance coverage if the company views you as a liability. As genetic testing gains popularity, insurability is just one of the consequences of finding out your disease risk.
Though screening can show if a mutation for a specific disease is present, it can't tell you if you will actually develop that disease. Nor can it tell you when the symptoms may appear or if they'll progress quickly. "It's not a guarantee [that you'll get the disease], but your odds are much higher," says Aletta Poll, a genetic counsellor at Women's College Hospital in Toronto.
The future of genetic testing
Genetic testing is still a new scientific tool, and the medical community acknowledges there's still plenty of research to be done to unleash its full potential. "There's a lot of promise in genetics, [but] we're at the beginning stages," says Babineau Sturk. In the meantime, each step takes us closer to a time when certain diseases have been all but eliminated, and medications tailored specifically to an individual's needs are commonplace.
In Rick Adler's case, the hope is that there will be a treatment for Huntington's disease. A month after his appointment, Rick's test results came back: He didn't carry the genetic mutation. "I was in shock. My mind was numb, but soon joyful tears came, and the first thing I did was hug my dad," he says. "Regardless of the test's outcome, on that day my life changed." If scientists have their way, many more lives will be changed thanks to genetic testing.
Want to get screened?
Canadians have the choice to be screened at hospitals, private clinics, or via mail-order kits. Screening eligibility varies from province to province, but most hospitals prioritize individuals who have a history of genetic disease in their immediate family, as testing is expensive and resources are limited. If you're accepted, your provincial health plan should cover the cost. Private clinics and mail-order kits are accessible to anyone willing to pay for them—costs can range from $200 for a kit to thousands of dollars for clinic screenings.
Genetic experts like Aletta Poll at Women's College Hospital recommend either a hospital or private clinic over a kit, because the former involve meetings with a genetic counsellor who will interpret the results for you. With a mail-in test, you spit into a plastic tube, mail it to a lab, then wait for your results to be sent back. Without guidance to interpret your results, it can be difficult to know what to do next, and the resulting confusion could have dangerous health repercussions for you and your family.
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|This content is vetted by medical experts |
|This story was originally titled "It's All In Your Genes" in the June 2014 issue.|
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