What you need to know before signing up for at-home DNA testing
Direct-to-consumer genetic testing first came on the market about a decade ago, but I resisted the temptation to see what health information is hidden in my DNA — until now.
As a molecular biology writer, I’ve been skeptical that the field of genetics is mature enough to accurately predict health (see related article). What finally motivated me to send away my DNA in the mail was the fact that companies are now offering much more genetic information. Is more better? Would an expensive test that deciphered my entire genetic instruction manual, or genome, reveal more about me than more limited tests? That’s what I wanted to find out.
For health testing, I sent spit samples to 23andMe, Genos and Veritas Genetics, three companies that represent the various levels of DNA testing available to consumers. (I did ancestry testing, too; you can read about my experiences with that in June.) These companies all analyze natural spelling variations in the string of letters that make up DNA. Where most people have, say, a “G,” some might have an “A.” Most of these genetic variants are harmless, but some raise the risk for certain diseases.
This story is part of a multipart series on consumer genetic testing. See the whole series.
Where these companies differ is in how much of the genome they assess and whether they look for only a limited set of known variants or can uncover new ones specific to an individual.
The DNA-testing process starts off the same for all of the companies I tried: ordering a kit online. Genos and Veritas both require a doctor to sign off on the test. 23andMe doesn’t, and as a result, the U.S. Food and Drug Administration limits the medical information the company can report. My doctor reluctantly agreed, but only because I was exploring DNA testing as part of my job. She said there was nothing in my personal health records or family history that would normally lead her to order a genetic test.
The kits all contained the same type of saliva-collection tubes. Sample prep was easy — register the kit’s number online, spit in a tube, mail in the sample. I also opted to let each company use my DNA in research studies, which required an extra step of answering a questionnaire about myself.
Within a couple of months, 23andMe and Genos emailed to tell me my results were available online. Because of a technical glitch, it took about seven months to get results from Veritas. The company says the typical wait time is closer to 12 weeks. Veritas also sent a copy of its report to my doctor.
23andMe uses the oldest technology, called SNP genotype testing. SNPs, short for single nucleotide polymorphisms, are the spelling variations in DNA. For $199, 23andMe examines about 690,000 predetermined SNPs. That may sound like a lot, but it’s only 0.01 percent of the 6 billion DNA letters in the human genome. It’s the genetic equivalent of spot-checking a few letters in each chapter of War and Peace and trying to decipher the plot.
- Explains results well
- Examines a limited set of variants
- DNA may need to be retested as new genetic discoveries are made
Still, the company can tell you interesting things about some physical and physiological traits, like cleft chins, dimples or the ability to taste bitter flavors. And 23andMe has FDA approval to report on a few health conditions linked to specific genetic variants, such as celiac disease and macular degeneration.
The problem is, the company tests only a small subset of all potential SNPs. Getting a report of “variants not detected” doesn’t mean you don’t have any variants related to a particular medical condition. It just means you don’t have the ones tested for.
On the plus side, 23andMe provides clear explanations of what it does and doesn’t test for, and lists other factors that contribute to disease risk. In fact, 23andMe does a far better job than Genos or Veritas of explaining what having specific genetic variants means.
Genos offers broader testing, for $499. It reads, or “sequences,” every letter in a person’s protein-producing genes. By deciphering this Cliffs Notes version of the genome, called the exome, Genos can theoretically find genetic changes that are unique to an individual, though the significance of these finds for health isn’t always clear.
- Provides the most raw information
- Provides little to no interpretation of findings
Compared with the other two services, Genos gave me the most data but the least useful information. The company found 44,225 variants in my exome and showed me how many are on each chromosome. But Genos provided information for just 4,294 of them because those variants are in ClinVar, the publicly available database that Genos draws information from.
And even for these variants, Genos gave few details — like how common the variants are and whether they change one of my proteins. The company offered almost no interpretation of what the variants mean for my health, other than to classify how harmful they might be: pathogenic, likely pathogenic, likely benign, benign or unknown significance. Most frustrating, Genos didn’t tell me which diseases these variants are associated with. I would need to explore the scientific literature myself to figure this out. So for most people, Genos’ report wouldn’t be that useful.
The company did, however, have more to say about how my variants influence a variety of my traits, such as hair and eye color, freckling, several characteristics of my ears and my ability to smell cut grass, roses and sweat. Genos also reports how genetics can affect a few behavioral characteristics, such as a tendency to overeat and the propensity to worry.
Finally, Veritas charged $999 to read nearly every letter in my genome, including portions in between genes that regulate gene activity and parts containing noncoding RNAs, which do a variety of cellular jobs. Those sections between genes are proving to be lush territory for discovering health risks.
- Offers the most health information
- Can find variants linked to gene regulation
- Reports only the findings that the company considers medically relevant
Not surprisingly, Veritas gave me the most wide-ranging report. For instance, only Veritas shared “pharmacogenomic” information — how my genetic variants could influence how certain drugs affect me. The list of drugs my genes may or may not play well with is long. I take only one drug on the list, but I’m glad to have all of this information in case it becomes relevant in the future.
While Veritas has nearly the entirety of my genetic information in its data banks, the company told me surprisingly little. Turns out, I’m just not that interesting, genetically speaking. The company screened more than 40,000 genes (including the noncoding RNAs) but found no big health risks — at least, none that scientists can reliably predict today.
The company did cover a more extensive list of physical and physiological traits than either Genos or 23andMe did. Veritas’ focus is on medically relevant information, though, so the traits tended to be practical: for instance, how prone someone might be to tendon injuries, how muscles would respond to exercise, and how one’s genes might affect blood sugar and cholesterol levels.
One thing I discovered from all this testing is that the companies don’t necessarily tell you everything they find in your DNA. Veritas, for instance, sometimes doesn’t report certain information that it doesn’t consider medically relevant. But that decision could have medical consequences.
I learned from 23andMe, for example, that I carry a variant linked to hemochromatosis, a disorder in which excess iron in the blood can build up and damage organs. My variant is unlikely to cause me harm, but it could be a problem for any future children if they also inherited a different harmful variant of the gene from their father. So that’s useful information to have if planning a family. (And indeed, my husband carries this variant, though the odds of us having a child with this disorder are still low.) My Veritas report did not mention the variant. When I checked with the company, Veritas said it chose not to report this variant because of its low likelihood of causing me trouble. But I would prefer to have that information.
Overall, none of these genetic testing companies give you complete information about your health and genetics. Veritas may give you the most bang for your health care dollar, but its report is definitely not as user-friendly as 23andMe’s. Unless you’re a hard-core genetics nerd like me, Genos in its current form could be a frustrating experience.
Before you decide to get your DNA tested for medical reasons, talk to a genetic counselor to see which level of sequencing best suits your needs. If testing uncovers something worrisome, the result should be confirmed by a doctor. Keep in mind that genetics is an inexact science. Someday it will be better. If you can wait for that day, you may have a more satisfying experience. If you just can’t wait, take the results with a grain of salt and keep an open mind. As scientists learn more, interpretations may change.
Which test is right for you?
Here’s how the companies compare.
|Service provided||SNP genotype testing||Exome sequencing||Whole genome sequencing|
|Saey’s wait time||Four weeks||Nine weeks||Seven months*|
|Requires a doctor’s order||✔||✔|
|Opt-in for research||✔||✔||✔|
|Allows download of raw data||✔||✔||For $99|
|Provides information on:|
|-Physical and behavioral traits||✔||✔||✔|
Editor's note: This story was updated May 22, 2018 to correct the illustration of DNA in the image at the top of the page.