Genetic Testing
I have been reading a lot lately about all of these new genetic tests that are becoming available. What are the kinds of tests that are out there? When should someone get one of these genetic tests?
- A curious adult from California May 02, 2008 Those are some very timely questions. There are more genetic tests available today than ever before. You can take genetic tests for medical reasons. Or to look at family relationships like paternity testing or tracing your ancestry. And now, there are even tests you can take just for fun that look at hundreds of thousands of different places on your DNA all at once. All of these choices can make it hard to decide which test (or tests) to take. Or whether you should get a genetic test done at all. To help, I'll first go over some things you might want to think about before getting a genetic test done. This is obviously not a complete list but will hopefully get you thinking about some possible consequences and limitations of genetic tests. Then I'll discuss some of the different tests available. Things to consider before getting tested If you are thinking about getting tested for medical reasons, it's best to work with a genetic counselor. They can help explain the results and deal with the choices you may need to make. I've listed some of the issues a genetic counselor might bring up or that you might want to consider before getting tested below. After reading them over, I think you'll see why a genetic counselor might come in handy!
  • What will you use the results for? How might the results impact your lifestyle?
  • Results of the test will also apply to family members. How might they feel about these results?
  • It's possible that you may get unexpected results like finding out that who you thought was your father is not genetically related to you. Is this something you can deal with?
  • How would you feel if you find out that you don't have an increased risk of a disease but your brother or sister does? Or vice versa?
  • How will others use your genetic data if you choose to share it?
  • Can you be fired or refused insurance based on your genes?
  • How much will it cost?
  • Results may not apply to you if the links between the genes and the effects were studied in a group from a different ethnic background
  • New research may change the interpretation of results
  • The results may only reveal a change in risk for a disease and not whether you will definitely get the disease
As you can tell, it's important to really think through the decision to get genetic testing. The tests can give you a lot of information. But, the effects the tests results can have and interpreting what that information means for your future can be tricky. (Click here to see what different test results could mean) When should you get a genetic test? Unlike getting tattoos or buying lottery tickets, there is no minimum age for getting a genetic test. In fact, genetic tests can be done at any age. Tests are even done on fetuses to figure out if the developing baby has any genetic problems. But, when to get tested really depends on why you are getting tested. If the test is for a disease that doesn't appear until later in life (like Huntington 's disease), doctors and genetic counselors advise NOT testing kids under 18. The person getting tested should be mature enough to make his or her own choice. There are major issues to consider before jumping in and deciding to know whether you are going to get a life-altering disease. Especially if there is no cure for the disease. Kinds of Tests You Can Order Medical Tests There are actually many different types of genetic tests that can give you medical information. These tests tend to focus on a single gene for a single disease. As I said, for these tests it is best that a genetic counselor be involved. Or at the very least that the DNA testing company make genetic counselors available to you. Most people probably think about predictive testing. These tests look at your DNA and predict your chances for getting a disease. You can also get tested to confirm a diagnosis. Another common type of medical genetic test is carrier testing. Many couples get tested before having children to find out their chances of passing on a disease to their kids even if they don't show signs of having any disease. Click here for more information about carrier testing. This article also mentions genetic tests that can be used to predict how a person might respond to certain drugs. While most medical genetic tests will be ordered through your doctor, there are companies like DNA Direct that offer these types of single medical tests to you directly. DNA Direct offers the services of genetic counselors and offers many well validated tests. Another company that offers genetic counseling services along with its testing is Navigenics. This company looks at almost 2 million spots in your DNA to tell you your risk for about 20 different diseases. The diseases this company looks at are very complicated and so the results are difficult to understand without a genetic counselor (or even with one!). Scientists also do not fully understand these diseases and so it is important to know that any of these tests will not give concrete results. For example, these tests can't tell you that you will for sure have a heart attack. They can tell you that given our current understanding and your set of genes, you have an increased or decreased risk for a heart attack. They can even give a number to that increased or decreased risk. Remember too that these tests are based on current interpretations of data and that new data can change the interpretation. And that scientists are constantly generating new data. To deal with this changing landscape, Navigenics charges an additional yearly service fee to update you on what new research means for your particular case. Tracing Family Relationships: Paternity and Ancestry Tests Paternity Paternity tests compare a child's DNA to that of a potential dad's (or other relatives if the dad is not available). The test compares lots of sites in the DNA to see how many match. (Click here to learn about these different sites and how they are compared.) Almost all need to match to tell if someone is the real dad. Of course, like all genetic tests, these are not foolproof. Ancestry An increasingly popular use for genetic testing is trying to use them to figure out your ancestry. The tests can be pretty limited and can usually only tell you a bit about your past. But when they complement genealogical family tree building, they can be pretty useful. See the following previous articles for more details on ancestry testing: Recreational: Personal Genomics A few companies recently started to offer "personal genome services." This means that, for about $1000, you can take a look at 500,000 to 1 million unique spots in your DNA. We're coming to a time where anyone (with some money) can take a look at their whole DNA code. As I said before, most medical genetic tests only look at one or a few genes. These new companies are looking at many different areas of your DNA all at once. This includes lots of different genes! So, what the test results mean can be even more confusing.

Microarrays are used to look
at many DNA differences
at one time.
Of course, if the tests are just being taken for fun, then any confusion isn't a big deal. Knowing whether you have the wet earwax variation of a gene is not as serious as knowing whether you have an increased risk for breast cancer. So, as long as you aren't taking these tests for any medical reason, it can be fun to know more about your DNA. I'm always interested in learning more about myself. And, what's more personal than learning about your DNA, the instruction manual for you? Right now though, these personal genome service companies give you information that's more like a personality quiz than for medical planning. You can learn more about your ancestry (or at least how similar your genome looks to those of people from different areas of the world) and your physical appearance (are you carrying a gene for red hair that you didn't know about?). These companies (like 23andme and deCODEme) also tell you about your risk for some diseases. But as we've talked about before, it can be hard to know what that means even with the help of a genetic counselor (and they do not offer genetic counseling as part of their services). If you are thinking about trying out one of the new personal genome services, remember to take the results with a grain of salt. We are still far from knowing how exactly all the differences in our DNA sequences work. Conclusions Deciding to get a genetic test is not a simple decision. Planning for a healthy future can include getting genetic tests. But the results can have impacts on your life that you aren't prepared for. For example, even the result of a genetic test that is fairly straightforward (like Huntington's disease) comes with baggage. Since we have no way of preventing or curing HD, you need to think about how a positive result could change your life. Do you want to know the result? A positive or negative result for any genetic test can have a big impact on you and your family. So, it's important to think about what those results might mean for you before deciding to get a test. Jennifer Shieh