Dear Jeanie: Whole Genome Sequencing

Editor’s note: The “Dear Jeanie” blog series uses fictional patient questions written by an NSGC expert based on her experiences as a genetic counselor. This series in no way represents a real patient or single genetic counseling session.

Dear Jeanie,

Recently, I read in a newspaper article that I would soon be able to get my entire genome sequenced for less than $1,000.  That’s crazy!  Is this true?  I thought that genome sequencing would cost like a billion dollars.  Should I do it?

Sincerely,
Dora the DNA Explorer
 


 
Dear Dora,

It DID cost a billion dollars not so long ago!  Three billion dollars for the first one, actually.  The cost of sequencing a genome dropped from $10 million in 2007 to $1,000 in 2017.  If the cost of New York City real estate would do something similar, Jeanie could afford to live in the West Village and still buy shoes at Barney’s.  Buyer beware in this and all things, but there is a lab that is certified to offer clinical-grade testing and will sequence your genome today for $1,000 (with the approval of your doctor), and it’s safe to assume that the price will only go down.  For realz.

Should you do it?  The answer depends on what you’re hoping to achieve. You might be thinking about having a child, and want to know what sort of things you are at risk of passing along.  You might be looking to use your genome for your own health and wellness, to understand what your chances are to develop a disease or to explain why you have a certain medical condition.  Getting your genome sequenced can help but, depending on the situation, there may be less expensive tests that are designed specifically for your purpose.   Or does your genome simply seem like a cool thing to possess?   Is the “cool-factor” of having your genome on a hard drive worth $1,000?  If so, far be it from Jeanie to suggest otherwise.

But read the rest of my answer first.

If you have an existing medical condition, you should ONLY pursue genetic testing in the context of medical care, with advice from someone specializing in genetics, because otherwise there’s a good chance you won’t get the right test.  I hear you asking, “My dear Jeanie – how is that possible?  Why would another genetic test be different from whole genome sequencing? Doesn’t whole genome sequencing cover everything?” Those are very reasonable questions.  The answer is that the raw data is the same, but the interpretation of the data can lead to very different results.

When we read a genome, we never see the entire thing.  It’s a book that is way too long to read in full, so we rely on programs that give us a highlighted version.  These programs are designed to ignore a lot of the variation that is not already known to be dangerous, because if you are healthy, it is probably okay.

When there is a medical reason for a genetic test, we alter the program to look more closely at the genes that are our prime suspects.  So, by design, a whole genome analysis that is not optimized for your particular medical issue may overlook the key piece of information that explains your condition.  It’s like scouring the city by drone to search for your lost phone, but failing look under the bed or between the couch cushions.

If you don’t have a medical problem, the type of information you can get from sequencing falls into three buckets.  First, there are clear cut findings of immediate medical significance to your health.  To qualify as ‘medically significant’, we have to be able to give you reliable information about what the risk is and how likely it is to happen.  In some cases, there are things you can do to protect yourself.  This is a very important bucket, but not a big bucket.  Experience suggests that today, about 1 person in 50 will fall into it and that percentage is increasing as we learn more about the relationship between genes and disease.  If you are that 1 in 50, you may very well feel that getting your genome sequenced was a wise decision.

Another giant bucket is full of findings that don’t mean much.  All those little differences do make you unique, little snowflake, but they don’t necessarily make you interesting.  Which is just fine, because while you want to be interesting at a cocktail party, you don’t want to be interesting to your geneticist or genetic counselor.  “Interesting” is our code word for “uh-oh.”

Finally, there is a great big bucket of I-don’t-know.  These include findings that might be bad, but they might be nothing, or ones that appear to be associated with a genetic condition but not all the time.  Perhaps they are subjects on which experts disagree.  Also in the bucket of I-don’t-know are the findings where we have an idea of what it means, but we don’t know what to do about it. This is a pretty big category, and things that fall into this bucket can be frustrating.  What you might hear is something like: This might raise your risk of such-and-such disease, but I’m not certain, so why don’t you have your doctor do this test or that test twice a year but otherwise try not to think about it…  Or: Well, we didn’t think that was compatible with life but here you are, so obviously it must not be so bad.  Lucky you!

This is a very roundabout way of saying, Dora, that I cannot tell you whether or not you should sequence your genome.  I will tell you that most people trying to make sense of their genome will have a lot of questions, so the test is much more likely to be useful if you are in a position to get answers to your questions.  Do you have awesome Google skills and enjoy reading medical literature?  Does your primary care doctor have a lot of patience and an interest in genomic medicine?  Does a noted research scientist live next door and frequently come over to borrow your power tools?  If the answer to all these questions is no, then make sure you have a plan for how to get help if you have an “interesting” result.  Keep in mind that the cost of genome sequencing is separate from the cost of good interpretation and counseling, so be sure to factor that into your budget.  Without good counseling, genomic data can be confusing, hard to use, and even misleading.

The genome is still largely uncharted territory, Dora.  If you’re up for the unknown, by all means, get your genome sequenced now.  If you’re uncertain, you should wait.  Your genome isn’t going to disappear like polar ice.  Technology will improve, interpretation will get better, and everything will get cheaper.  If you really want to be an explorer, go now – but take along a guide!

Yours truly,
Jeanie

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