What DTC Genetic Testing Can—and Can’t—Tell You

This week, Mary Carmichael of Newsweek is exploring the world of direct-to-consumer (DTC) genetic testing and deciding whether or not she’d like to find out about her own DNA information.

23andMe was asked to contribute a short piece on what you can—and can’t—learn from services such as ours.  We were more than happy to help, as it is our firm belief that education is a critical first step toward our goal of meaningful integration of genetic information into clinical care.   Below is an expanded version of what we wrote.

If you’d like to join the conversation, leave a comment over at Newsweek, or follow Mary on Twitter and let her know what you think.

 

Get the Right Drug at the Right Dose

 

What we can tell you: Genetics can impact whether you’ll need more or less of a medication compared to most people, or whether you might be at increased risk for serious side effects.

For example, the blood thinner warfarin (Coumadin®) can help prevent blood clots, but it can also cause excessive bleeding in people whose sensitivity to this drug is increased by two genetic variations covered by 23andMe.   There are also genetic effects on clopidogrel (Plavix®) efficacy.  Normally this drug helps prevent heart attacks by keeping blood cells from sticking together. But a genetic variation that interferes with the drug’s metabolism prevents some people from getting the full effect, putting them at increased risk for cardiovascular events.

What we can’t do: DTC genetic testing can’t replace your doctor when it comes to making decisions about how best to treat you.  There are many factors other than genetics that need to be taken into consideration.  No one should stop taking a medication or change their dosage without a doctor’s supervision.

The Future: Mutations that Could Impact Your Children

What you’ll learn: If two people are carriers of certain disease-causing mutations, each child they have together will have a 25% chance of being born with the disease.  Knowing a child has a chance of being born with one of these diseases can facilitate early intervention and improve outcomes.

One in 29 people of European descent carries a mutation that can cause cystic fibrosis.  Approximately one in five Ashkenazi Jews carries a mutation associated with a severe disease that could result in the early death of a child, such as Tay-Sachs, Canavan disease or Niemann-Pick disease type A. Sickle cell anemia occurs in about one out of 625 African Americans and one out of 1,000 Hispanic Americans.

23andMe tests for mutations associated with these and many other inherited conditions.

But remember: For almost every inherited condition, there are many, many known mutations.  Some of these are more frequent than others, and the chance of having certain mutations often varies by ethnicity.  All screening tests necessarily cover only a subset of the possible mutations for each disease.  Because of this, these tests can tell you that there is a chance that a child will be affected, but if no mutations are detected you don’t know that a child absolutely won’t be affected.  The presence of undetected mutations in each parent could still lead to a child being born with the disease.

Common Diseases – the Future of Genetics

 

What we know: Common DNA variations found within all of us have been linked to increased risk for things like diabetes, cancer and autoimmune conditions. Learning your genetic risk for these conditions allows you and your doctor to focus on what matters most for you.

What’s left to figure out: The genetic variations identified to date explain only a small part of a person’s risk for each disease.  Unknown genetic factors, as well as environment, are also important.  Additionally, because most research is conducted in populations with European ancestry, people from ethnic minorities get limited information from DTC genetic testing.

Through its research, 23andMe is working to improve the information that all people can get from their DNA data.  Our 23andWe surveys allow everyone to contribute to work aimed at understanding some of the most basic facets of our biology, and have already resulted in the publication of a report in a peer-reviewed scientific journal.  Our Parkinson’s disease and sarcoma communities are bringing people from around the world together in a participant-driven effort to make real strides in our understanding of these diseases.

We are also partnering with several groups in order to increase the diversity in our database and, in turn, the number of results we will be able to provide to all people, regardless of their ancestry.

The Fun Stuff

Some of the information hidden in your DNA is just plain cool!

 

Physical Traits: Is your earwax wet or dry?  Never thought about it?  Well, you will once you learn about how just one little letter in your DNA can make all the difference.  Your eye color, hair curliness, whether your sneeze upon entering bright light, and the ability to smell asparagus in your urine (ewwwwww!) are also all influenced by genetic factors.

Ancestry: Locked within your genetic code are both the story of your ancestors and the information you need to fill in your family tree.

Ancient Migrations: With state-of-the-art tools 23andMe traces maternal ancestry back tens of thousands of years with a small piece of DNA passed down from mother to child. Males can uncover their paternal ancestry through the Y chromosome that is passed down from father to son.

Global Origins: By comparing your DNA to reference populations from around the world, 23andMe can give you clues as to where each piece of your genome originated and which populations you are most similar to.

Find Relatives You Never Knew You Had: 23andMe’s Relative Finder lets you find all the other 23andMe members who match your DNA. You can browse and make contact anonymously.  Most people find over 100 “cousins,” though this varies based on ancestry.  People who have mainly European roots may find several hundred relatives. If you have Ashkenazi Jewish ancestry, you might find well over a thousand.