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Direct-to-Consumer Genetic Testing

For the last 10 - 15 years, direct-to-consumer (DTC) genetic testing has become a very popular tool for ancestry testing as well as determining disease risk. There are a lot of misconceptions in the public about what these tests reveal, and how accurate they are. Several years ago I was chatting over Thanksgiving dinner with my cousins about doing 23andMe testing. Their reason for doing it? "It's fun!"

As I always do, I asked "what's fun about that?" I didn't mean to be rude or obnoxious. But I've never understood, from the perspective of a genetic counselor, why this is fun. The fact of the matter is that genetic testing has tremendous potential, and has provided unprecedented medical information for human (and animal) kind. But this is when it is done in a controlled, targeted way.

I am not implying that the general public does not have a right to genetic information about themselves or their families. Certainly they do. The problem lies in the marketing of these tests; what the companies seem to portray their tests can do, and what they actually do, can be different.

They can be somewhat helpful in determining a person's ancestry, in a very general way. I would not use the word accurate to describe these tests, although at the continental level -- African, European, or Asian, for example, they do a reasonable job. If you're told you are 93% Italian, for example, your background is likely mostly European. But I would defy any genetic test to be able to tell you whether you're from Italy, Spain, Portugal or the Netherlands! If you're of an ethnic group that long ago was isolated from others due to social status, geography, or any other human condition, it may well be more accurate. Groups such as those of Ashkenazi Jewish or Icelandic descent fall into this category. By virtue of being isolated, the genetics of the people in each group tend to be more similar to each other than to those outside their groups.

​From the standpoint of disease prediction, athletic stamina, or the ability to metabolize certain foods or medications, these tests are not particularly accurate - yet.

Janice Berliner, 2019

From the standpoint of disease prediction, athletic stamina, or the ability to metabolize certain foods or medications, these tests are not particularly accurate - yet. I have little doubt that they will be, and have tremendous potential. But as our knowledge of genetics stands at the moment, one could theoretically take the same test from two different DTC genetic testing companies, and have wildly different results. This is based on the testing methodology, which looks at certain markers within our DNA. If the labs are looking at different markers, they may end up with different results. So one lab may tell you that your risk for lung cancer is increased, while the other might tell you it is decreased.The problem is, of course, that we certainly would not want anybody with a decreased risk for lung cancer to think that he or she could smoke like a chimney without risk of developing cancer.

Finally, the DTC laboratories will warn you in the fine print that these tests can reveal information that you may not be looking for. But we all know that most people don't read the fine print, may not think it applies to them, or may not believe that they would ever find themselves in the small percentage who end up with a negative outcome. Families have been torn apart when non-paternity has been revealed, or adoption, or long lost half siblings, etc. Again, I don't mean to imply that this testing doesn't have value, or that it doesn't have potential. But I do think it's important to consider the implications prior to undergoing testing.

Good news is, you don't have to figure out everything on your own! Genetics professionals across the country are available to explain the details of direct-to-consumer testing to you if you're interested, and are also available to decipher the results once you have them. So if you've done any of these tests and do not know what they mean, don't hesitate to contact a genetic counselor in your area. It's entirely possible that the results will tell you something different from what you thought.

To find a genetic counselor in your area, go to NSGC.org and click on "find a counselor."

And for more information, this article is really helpful: https://doi.org/10.1016/j.mayocp.2017.11.001


Genetic Mythbusters Part I

Genetic Mythbusters Part II

The Why, Not The How, Of Prenatal Testing 

Ask Me Why Being a Twin is Not Cute!
Genetic Mythbusters - Part II

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