* This thread is NOT medical advice! Ask your health providers about medical concerns! Also, I’m referring to folks 18+ since personally I don’t think parents/guardians should order DTC testing on minors. That could be a whole thread on its own, so I’m leaving kids out of this.
1) I don’t think telling people not to do things is the answer. I believe people should have access to the info they want about their health & DNA (Though informed choices are key! And I wish there was better access for more people so that DTC didn’t seem like the only option)
3) So what’s this “fluff” you may find w/ DTC genetics? Whether you have red hair 👩🏼🦰 if you like cilantro 🌿 where your ancestors were from 🌍 (ok so sometimes that one’s not fluff) - you likely already know this info. And if it’s wrong about your hair color, well then it’s wrong
4) Because of FDA regulations & the technology they use, DTC genetic companies don’t give out a lot of non-fluff info. For example, they report risk for diabetes, but it’s a risk estimate, not a diagnosis. Most common disease is multifactorial anyway - due to genes & environment
5) DTC tests usually look at single nucleotide polymorphisms (SNPs) across your DNA. SNPs are common, but vary across populations. One SNP typically has a small effect. Looking at many SNPs in many people & comparing to traits can show associations, but they’re not deterministic
6) Contrast to clinical tests I order to diagnose patients, which are focused on Mendelian conditions (a single can cause a disease with high penetrance) & sequence (read letter by letter) curated lists of disease genes instead of just scanning for certain variants
7) But just because DTC genetics is the crazy fun aunt of clinical genetics doesn’t mean you won’t learn unexpected or important things about your health/family. I tell everyone: Don’t do DTC genetics if you don’t want to find out your dad’s not your biological father (seriously)
8) What other family #DNAsurprises might you learn from DTC genetics? You have siblings or cousins you didn’t know about; your family is from a different part of the world than you thought; you were donor-conceived. These can be shocking/upsetting (though not always bad)
9) You can opt out of connecting to relatives, though some people do DTC tests specifically for answers about family (e.g. adopted folks or donor-conceived folks). There are lots of sad and happy and heartbreaking and uplifting stories about folks navigating DTC surprises...
10) See: nytimes.com/interactive/20… or also podcasts.apple.com/us/podcast/the… (@beaglelanded episode w/ Kif Augustine-Adams) or amazon.com/Inheritance-Me… (Inheritance by @danijshapiro)
11) Good news - there are resources for people navigating DTC surprises. Main things that come to mind are powered by @GCBrianne like her resource site/counseling service Watershed DNA watersheddna.com & book w/ @tntfamhist #DNAGuideforAdoptees dnaguideforadoptees.com
12) Also, though DTC companies are blocked from doing a lot of health-related tests, there are some legit genetic conditions you may learn about: you might learn you have a disease-causing BRCA1 variant, your risk for Alzheimer’s is elevated, you’re a carrier for cystic fibrosis
13) ⬆️ Those results may have big implications (though they should be confirmed & there are nuanced details re: risk & actionability). Some people are ultimately glad to learn this stuff (see statnews.com/2019/08/08/23a…) and some people aren’t so sure (see heraldnet.com/nation-world/g…)
14) It’s not ideal to find out important health info from a mail-in spit kit, but I think the real downfall of the popular health-related DTC tests is they’re not comprehensive ❗️Negative results don’t mean low risk❗️They’re not comprehensive cancer, carrier, dementia screening
15) Clearly folks want more info, though. Some curious/savvy people download raw DTC data to 3rd party websites like @promethease that scan the raw data file for potentially disease-causing variants in genes that weren’t on the DTC report. Now this is the real can of worms...
16) @promethease recommends to “confirm any significant finding discovered in part through the use of Promethease by an independent, clinically validated test” but don’t make it clear that ~40% of the findings are FALSE POSITIVES (See @AmbryGenetics paper:nature.com/articles/gim20…)
17) False positives from raw DTC data can lead to quite the scare. See @laurahercher’s article re: @mjfender’s experience: nytimes.com/2018/09/15/opi…
18) Again, good news is that awesome genetic counselors are helping folks navigate this process. Thanks to @EllenMatloff & @MyGeneCounsel for creating resources for patients with DTC raw data findings and pathways to clinical confirmation (eg through @AmbryGenetics)
19) For above reasons & more (like how DTC companies pretend like the test is a window into your health when really it’s a peephole at best), consumer genetics has been called the “biggest health scam of the decade.” See: gizmodo.com/consumer-dna-t…
20) But I get it. People really want to understand genetics of health. And many people do in fact have Mendelian/single-gene conditions running in their family. It can be hard to figure out what testing is right or what provider to go to... so people do DTC just to see
21) For specific questions like “is the cancer in my family hereditary?” or “am I a carrier for any recessive conditions?” the DTC test you can buy at CVS is NOT going to cut it. Going through a healthcare provider or a genetic counselor (findageneticcounselor.com - yay!) is ideal
23) LONG story short, it’s hard to answer that cocktail hour question “Should I do 23andMe or Ancestry.com?” Clearly, I have a 20+ tweet response and would prefer a 15 min convo & taking a 3-generation pedigree before answering 😂 Because it’s complicated!
24) My takeaway? Sure, do it if you want. Know there can be uncomfortable surprises (but there are resources to cope w/ or follow up on results). Think twice about buying for someone else (they may not want this info). And think extra hard about uploading raw data. Ok, I’m done. 
*single gene
25) Ok ok one last Tweet on this topic to note that I didn’t even get into privacy or discrimination concerns related to consumer genetics (mainly because I’m still wrapping my head around these topics!) See bloomberg.com/news/articles/… & forbes.com/sites/ellenmat… for some thoughts
