At-home DNA tests — what can they tell you?

Norman Swan: So, Tegan, have you done your DNA to find out where your ancestry came from, or what diseases you’ve got?

Tegan Taylor: I don’t need to do a DNA test to know that, because someone in my family did one of those family history or family tree things back in the day, and apparently the first of my kin to come or at least one strand of them to come to Australia, I think they might have been convicts. They were called the Crapp family. So that gives you all you need to know about my…

Norman Swan: Isn’t that the name of the family from The Sound of Music?

Tegan Taylor: No, that’s the von Trapps…

Norman Swan: Oh, von Trapp, not Crapp. Okay, fine, sorry, I thought you might have Austrian or…

Tegan Taylor: No, my ancestry is poop.

Norman Swan: My brother did it…

Tegan Taylor: But then you don’t have a choice. He’s given away your DNA… oh, we’re going to talk about this.

Norman Swan: No, he did his own DNA, but he found out he was 12% Greek, and so I tried to convince Patricia Karvelas on Radio National that I was 12% Greek, and for some reason she was a bit sceptical, although I said yassou, you know, but apparently I even pronounced yassou wrongly. So much for my DNA experience, and your DNA experience, von Crapp, von Trapp, whatever your name is.

Tegan Taylor: Well, DNA testing is what we are going to get into in all its facets today here on What’s That Rash?.

Norman Swan: The podcast where we answer the health’s questions that simply everyone is asking.

Tegan Taylor: So today we have questions from Richard, Kasha and Janet, all asking about DNA testing. Richard says, ‘I’m considering doing a commercial DNA test to learn about potential health problems, how to avoid them, and what solutions might help address existing problems. Is this gene testing something that’s worth doing? How do I avoid the bad actors I suspect are out there?’ Kasha says, ‘Would you explain DNA testing kits? Are they reliable? If the results are implemented, will I obtain better health outcomes?’ And Janet says, ‘So many people I know are being tested to determine their ancestral heredity. They suddenly know they are 24% Norwegian or Scottish. Is this reasonable?’

Norman Swan: Well, only if it’s Scottish.

Tegan Taylor: Are you 24% Scottish?

Norman Swan: I am 0% Scottish, but that’s another story. 

Tegan Taylor: Well, you’re 12% Greek, I know that. Scientifically possible? How is it done? So yes, we’re being asked here about a couple of different types of tests, but really they’re all doing something similar. 

Norman Swan: Yeah, I think there’s quite a lot on the market now. So you send back saliva or a swab of your cheek, and you send it off for testing. And there’s a misunderstanding about what these tests do. So this is not genome sequencing. This is not sequencing every gene and every bit of DNA to find out what mutations you might have in your total gene sequence. What they test for are what are called SNPs, single nucleotide polymorphisms. This is really, by and large, what they do. They would argue that there are some exceptions to what they might do for deeper testing. But by and large they’re looking at these SNPs, and these are single genetic code changes in your DNA, throughout your genome, and they simply are like flags, markers of where genes are or might be in your genome. And some of these SNPs are associated with certain mutations, certain forms of genes. So they do this SNP testing, and then they compare that to what they call a reference panel. And that reference panel tells them that that pattern of SNPs in your genome suggests that you might have a particular form of a gene or not, as the case may be.

Tegan Taylor: Bear with me, Norman, I have never studied chemistry, I don’t know a lot about genetics. For others who maybe don’t have a PhD in genetics or medicine, what is the difference between doing a DNA full sequence and this SNPs thing you’re talking about?

Norman Swan: Well, one is cost, so the cost and cumbersome nature, even with modern technology, of doing a full genome, is a fairly massive undertaking and requires very sophisticated analysis, because what you come up with is not necessarily clear, and requires somebody to look at that and make sometimes a judgement call on what they find. But it’s going through the genetic code line by line of the DNA inside your genes and around your genes in each pair of your chromosomes. And this SNP, these single nucleotide polymorphisms, is much easier to do. They can do a survey looking for these particular polymorphisms. It’s much faster, it’s much cheaper, but it doesn’t look in depth at each gene. But there are reasonably tight associations between the patterns of SNPs and some genes. The question is how reliable it is and how comprehensively they capture those genetic abnormalities or genetic mutations.

Tegan Taylor: Then the other thing you talked about was a reference panel. Is that sort of like a group of people’s DNA that’s there to compare it to?

Norman Swan: Yeah. 

Tegan Taylor: How does one get on this panel?

Norman Swan: They build up their reference panel slowly and steadily, according to the people who’ve actually…

Tegan Taylor: Oh, so everyone who’s ever done…

Norman Swan: Yeah, it becomes part of the of the reference panel, particularly for their ethnicity. So the whole Norwegian, Scottish, Greek thing depends on the reference panel, the people who’ve actually used that particular company. The problem here is…and it’s changed over time as more and more people use these services, the reference panel becomes a bit more reliable, but the reference panels, notoriously in the past, have been biassed towards certain ethnicities, and therefore the chances that you are mistakenly attributed to a particular ethnic group depends largely on their customers over the previous years. 

Now, as they get more and more customers from a wider and wider range, a wider range of ethnicities, they probably get more accurate. But equally, if you find that you’re 24% Norwegian and you go to another DNA testing company, they might come up with a very different percentage because their reference panel is different. 

Now, the whole thing about SNPs and disease doesn’t just come from their own reference panel. It comes from a lot of studies that are done, so-called genome-wide association studies, where independently of these companies they study massive numbers of people and identify SNP patterns that are associated with certain risks for conditions like mental health issues, like depression for example, autism spectrum disorder, ADHD, coronary heart disease and other conditions. 

Tegan Taylor: So these are across one person’s genome, groups of genes or SNPs that tend to coexist within certain people?

Norman Swan: That’s right, and it’s because very few health problems are the result of a single gene going wrong. So if you have sickle cell disease, that’s a single gene going wrong. If you have cystic fibrosis, it’s a single gene going wrong, although within that gene there could be lots of different mutations, but it’s a single gene. Most conditions that kill us are multiple genes. Cardiovascular disease, cancer, although we will come back to the cancer genes like BRCA in a minute, which some of these testing companies say that they can detect. There are multiple genes involved, and therefore what you’re trying to pick up is a pattern of these SNPs that might be associated with a certain disease. They don’t guarantee they’re an association. And that’s one of the dangers here, is that they come back and might say you’ve got an increased risk of coronary heart disease, but is it that much more than the person next to you? If you do this test with another DNA testing company, are they going to find the same thing? Because it’s a pattern of SNPs rather than the genes themselves, the potential exists for errors.

Tegan Taylor: So, like you said, we will get to specific health screening, disease screening, in a second. But some of the testing kits that I’ve seen, they promise to give you unique lifestyle advice based on your DNA. There’s one company that says ‘personalise your daily routine with DNA, diet and weight management, fitness, sleep, vitamin insights and more’. I guess the question is, is there like an optimum healthy lifestyle mix for me and my specific DNA that would be different to you and your specific DNA? 

Norman Swan: Well, the answer is yes and no, and the answer is yes for some genes, like APOE4 which is a variant of the APOE gene…

Tegan Taylor: I don’t know her, who’s APOE?

Norman Swan: APOE is a gene that comes in various versions, and when you’ve got the APOE4 version, particularly in a double dose, in other words on both pairs of your chromosomes, it’s proven you are more likely to have developed coronary heart disease and you’re more likely to develop dementia. Therefore, if you change your lifestyle to reduce your coronary risk, you’re highly likely to reduce your risk of coronary heart disease disproportionately compared to some other person. But there are other genes that they detect, which some complementary practitioners say are really important for your diet, and they are often related to the amino acid methionine, and you’re told to change your diet, because this could change your life and affect your health outcomes, and there’s really very little or no proof for that. And so you can get led up the garden path, eating according to your genes. 

Tegan Taylor: I mean, eating a healthy diet is probably good for any of us. I guess the thing is if you’re being sold something, you’re being sold certain supplements or certain meal plans, people are making money off the fact that you’ve done this test. It also sounds a little bit like the blood type diet stuff that we talked about a few months ago, Norman, which we’ll put the link to that episode in the show notes for this episode. 

So I think the big one with these DNA tests, Norman, is…and we’re talking about…there’s like an acronym for it, DTCGTs, direct-to-consumer genetic tests. And so this is not something that your doctor has given you a pathology form for or anything like that. You’ve been able to buy this test, you do that yourself, you send it off to a private company, they send you some results. And there are direct-to-consumer genetic tests that can be folded into other, you know, ‘find out what ancestry you are’ kind of tests that say that they might tell you your risk of pretty serious diseases like the BRCA gene, as you said before, that greatly increases your risk of breast and ovarian cancer.

Norman Swan: Yep, hereditary prostate cancer, polyposis, colorectal cancer risk scores and so on, skin cancers. And in fact at least one of these companies has Food and Drug Administration approval to offer advice about genetic risk rather than necessarily genetic diagnosis. So the problem here is they give the illusion of accuracy and reliability when in fact they are not necessarily…they may be accurate in what they say, but they’re not necessarily reliable in telling you that you don’t have genetic risk. So let’s take BRCA…

Tegan Taylor: But also, like, they’re telling you about something that’s really serious. There was one screenshot that I saw of the page where it’s, like, you’ve sent off your cheek swab or whatever to find out how Indonesian you are, and then you open your app and it says you’ve got a BRCA gene variant. Like, that’s huge medical information to get from a third-party app, that you’re not kind of being given that information directly by a medical practitioner or a genetic counsellor who’s able to put that into context for you.

Norman Swan: Exactly. So, for example, if you take BRCA, there are many, many variants of BRCA. There’s about a thousand variants of BRCA, and one in particular, they only test for three of these variants, so they’re not picking up every variant of BRCA1 and BRCA2. And if they say you don’t have one of these variants, it means you don’t have one of the variants that they actually measure but you may have one of the other variants which increases your risk of breast cancer but you think you’re off scot-free. 

Tegan Taylor: Oh my gosh. Well, there’s actually an example of that that was published in a journal, a case study of a woman who that happened to. Basically she had a family history of two first-degree relatives who had breast cancer. She had the proper testing through the clinic, found out that, yes, she did have the BRCA gene. She had pre- and post-test genetic counselling, gold standard best practice. I don’t know if she had the risk reduction surgery or not, but certainly some of her relatives did. Anyway, so that’s the background. A year later, someone gives her one of these genetic tests as a gift, and she did it and it came back and said ‘you have a low risk of breast cancer’, to which she was like, ‘Well, I know that’s not true, because I’ve literally gone through this whole rigmarole a year ago.’ And so she got in touch with the surgery and relayed this story, asking for a bit more information. And, like you say, basically the test wasn’t testing for the particular genetic mutation that she had, but she said, and this is what they quote in the story, she said, ‘Honestly, if I had done this at-home test and not spoken to you, I may have received the results and thought I was off the hook.’

Norman Swan: Yeah. And the message here is that to assess your personal genetic risk is what’s running in your family, have you got a history of cancer being diagnosed in younger people, patterns of cancer like breast cancer, bowel cancer, ovarian cancer, prostate cancer in first-degree relatives? Then your GP sends you to a genetic counsellor to understand what the results actually might mean, because you can be spooked unnecessarily or reassured unnecessarily, and these things have enormous implications, including your ability to receive life insurance. 

Tegan Taylor: Well, the life insurance thing’s really interesting. You and I have spoken about this a couple of times before on the Health Report, this work that’s spearheaded by Jane Tiller from Monash University, arguing that life insurers shouldn’t be able to discriminate against people, insuring people based on their genetic risk…

Norman Swan: Well, their genetic testing.

Tegan Taylor: Genetic testing, correct, and that’s something that’s currently underway in Australia, whether it can be outlawed, that’s what they’re arguing for. And, in principle, everyone seems to agree with the fact that they shouldn’t be able to discriminate based on this testing but it’s not actually in law yet. 

Norman Swan: Yeah, as we record this, the federal government has had a recommendation to pass a Genetic Protection Act, and they haven’t yet acted on that. 

Tegan Taylor: And I guess it’s a little bit outside our normal remit, Norman, but when has that ever stopped us? Part of the concerns about DNA testing like this is that you’re giving away personal data that you literally can’t change. You can change your phone number if that gets leaked, but you can’t change your DNA. What about the privacy concerns here?

Norman Swan: Well, you’re sending it offshore, so the data are owned offshore. It’s been used for good in terms of criminal investigations. Another use of the DNA is to develop products, pharmaceutical products and others. And in fact 23andme has been facing bankruptcy because of its business model. People only do this once, they get their home DNA test and there’s no recurrent revenue, so 23andme developed a biobank and they developed other assets to try and make more money. And anyway, they’ve just been acquired, it’s subject to regulatory approval, by Regeneron, which is a pharmaceutical company, and they’re going to keep the personal genome service going, but they’re also hoping to use it in terms of research and development and develop new products.

Tegan Taylor: I mean, that’s great for the greater good, but maybe not what people thought they were agreeing to when they ticked yes to the terms and conditions.

Norman Swan: Perhaps. 

Tegan Taylor: So I think the thing with the disease risk is why would people do this and not just go to the doctor. I say that…so it’s so flippant, like, obviously some people can’t access medical care and it’s expensive and that sort of thing, but it’s not as expensive here in Australia if you have genuine reason to think that you’re at higher risk, because then often it is subsidised to have this sort of testing done. 

Norman Swan: Look, people are curious, they want to know. But the fact of the matter is if there’s a strong family history of coronary heart disease in your family, then you’ve got a risk that needs to be sorted out, and your GP needs to sort that out with you. And it may be that you are somebody who should have genetic testing. And just be aware that if you’re going to go off and get DNA testing done, and you’re doing it to work out ‘where did my ancestors come from, can I find a second cousin in Oslo’, that’s fine, and it’s a bit of fun. But if you’re doing it to actually get your disease risk, it’s not to be taken too seriously. By all means you take it to your doctor and work out what you’re going to do next.

Tegan Taylor: You don’t want to take it too seriously but you don’t want to take it too lightly either, because it can be discombobulating to find out this sort of stuff, either way, I think. I think understanding your genetic history and your genetic risk, there’s a reason why people who are professional genetic counsellors exist, it’s because it’s big, heavy stuff, and having a guide to lead you through it is really important.

Norman Swan: Yeah, and I suppose the proof of the pudding is in the eating; would I want to know my disease risk if I personally were to have one of these DNA tests? I’d do it to find out my ancestry for a bit of fun, but I wouldn’t particularly want to know my disease risk from that. I’ve got a fair idea from my family history what my disease risk is, and I’ve already taken action to deal with it.

Tegan Taylor: Okay, so on action, I’m interested to talk about behaviourally what we know people actually do when they do receive this information, because there has been research into this.

Norman Swan: It’s mixed. There have been some studies which suggest people are happy to receive the results and act on it and change their behaviour. But in fact a lot of research suggests that people get quite significantly distressed after receiving the results of their disease risk or supposed disease risk.

Tegan Taylor: I did see one study that said when people had a personal genetic test related to their health, the most common actions were seeking medical advice or doing nothing with the information, to which I said; what other options are there? One of the other options is seeking alternative or complimentary health advice. But yeah, you either tend to see your doctor or not to do anything. 

Norman Swan: I mean, I wouldn’t do nothing if they said we think you’ve got a high dose of APOE4, even though that’s been shown to have its own unreliability element to it. Or you’ve got BRCA, you know, if they find that you do have a BRCA variant, that’s probably a pretty accurate result, and therefore you do need to respond and take action, but you need counselling, and that should not be your first stop.

Tegan Taylor: So if you have one of these tests, it kind of sounds like no matter what kind of response you get, you still need to talk to a doctor to decode it. What’s the point in even getting the test to start with? This is really the question that we’re being asked by our correspondents. Is there any point buying one of these tests and doing one at home?

Norman Swan: For health reasons, almost certainly not. You know what to do, you know what to reduce. You’ve got to get your low-density lipoprotein cholesterol down. You’ve got to get your blood pressure down. You’ve got to eat a healthy diet that’s high in vegetables, low in red meat. And if there’s a strong family history of cancer or heart disease in your family, that’s what you’ve got to pursue, but you’ve got to pursue it with reliable testing and advice, rather than a home DNA test that relies on their algorithm and their computer, their reference panel of DNA testing, what they’ve taken into account from the scientific literature. You’re relying on a whole series of other stuff that may or may not help in the accuracy of your diagnosis.

Tegan Taylor: So when it comes to health stuff, tread with caution. When it comes to the ancestry stuff, maybe just a good excuse to go and take Greek lessons, Norman?

Norman Swan: Yeah, I now know why I like Greek salad and…but I don’t like Saganaki…

Tegan Taylor: Oh my gosh, are you for real? Saganaki is life! Maybe I’m Greek. 

Norman Swan: Maybe I’m only 2% Greek.

Tegan Taylor: Well, thank you so much, Richard, Kasha and Janet for the question. I hope it’s been at least a little bit useful, maybe a bit like a DNA test, it’s worth also talking to your doctor and not just getting your health advice from a podcast. But if you do have a question you want us to look into, you can email us, we are thatrash@abc.net.au.

Norman Swan: What’s in the mailbag? 

Tegan Taylor: Well, Jess says, ‘I am a dedicated listener of What’s That Rash? but sometimes I cheat on you with other health programs.’ 

Norman Swan: Flibbertigibbet!

Tegan Taylor: Anyway, Jess was walking down a sunny, crowded London street, cheating on us with Michael Mosley’s (RIP) Just One Thing, the inflammation special, when something strange happened. ‘They were talking about anti-inflammatory food, and the topic of diet came up. As expected, the guest said ‘Mediterranean diet’, and unexpectedly, yet automatically, I shouted, ‘Ding!’ at the top of my lungs.’ Jess says, ‘I then started laughing and looked like a complete maniac. Has anyone else self-reported this affliction?’

Norman Swan: Well, I can report I was giving a talk to about 400 people and I said ‘Mediterranean diet’, and three bells went off in the audience, so they were ready. 

Tegan Taylor: Where was this?

Norman Swan: This was in Melbourne. And also I interviewed somebody, it was actually Professor Henry Brodaty, about dementia prevention, and as soon as I said ‘Mediterranean diet’, he’d brought a bell into the studio and dinged it. So, Henry’s a fan too.

Tegan Taylor: I love it. It’s catching on. Well, Jess good to know that you’re not alone. Thank you for your devotion to us and to other health podcasts as well. You must be one of the best-informed people going around.

Norman Swan: See you next week. 

Tegan Taylor: See you then.