Consumer genetic tests reveal a range of health traits, from kidney disease to the potential for hair loss. But how reliable are the results?
There’s something thrilling about seeing your genetic results for the first time. Just to gaze at the raw data – the swirling list of adenine (A), cytosine ©, guanine (G), and thymine (T) – is to see the very code for your physical form.
It’s a spiritual moment – but it’s also a time to consider your health. DNA testing is now a mainstream healthcare tool. Major providers interpret the findings to offer a long list of healthcare insights. You’ll see at a glance if you have the genes for Tay-Sachs disease or cystic fibrosis.
There are many providers, including Helix, Bio-Synergy, and Nebula Genomics. The biggest provider is 23andMe. Spit into a tube, post it and two weeks later the 23andMe app offers around 100 health insights. These include 14 health genetic factors, 45 reports on carrier status – genes that may affect your children – and 37 traits such as the chances of having dimples, dandruff, toe length, early hair loss and eye colour.
The health information is rich – and sometimes disturbing. DNA tests reveal the presence of genetic variants associated with chronic kidney disease, hereditary haemochromatosis, and the dreaded BRCA1 and 2 variants for breast cancer, among others. The actress Angelina Jolie underwent a precautionary double mastectomy following a genetic test for breast cancer.
It’s a growing trend. More than 10 million people have taken the 23andMe test alone. So should we all be taking a DNA test? And if the results are so profound, why doesn’t the NHS offer such services?
“The bottom line is I haven’t done it myself,” says Sara Brown, a professor at the University of Edinburgh specialising in the genetic causes of disease. “That should tell you something about how highly I value it. We’re all keen to have the equivalent of a crystal ball. So I can totally understand why people want to do it. But would I ever recommend it to a patient? I wouldn’t.”
Brown explains that genetics is almost always too complex to be reduced to a set of results delivered via an app. “The uncertainties make it really difficult to recommend for a specific question.” For example, look at the likelihood of contracting a disease: “If you have an 80% risk, you’ve got a 20% likelihood you won’t get it. How then do you use that information in your everyday life?”
Factor in lifestyle, environment, and umpteen other genetic variables, and the gap between genes and real-world outcomes become perilously uncertain. “Very, very few diseases are a single gene,” she warns. “The vast, vast majority of human diseases are related to multiple genetic effects interacting with each other and also interacting with multiple environmental factors.”
In fact, this is the same line taken by 23andMe. While the headline results are clearly presented, each finding is linked to a wealth of further information, filled with caveats and context. For example, the BRCA1 breast cancer result states in bold writing that while three genetic variants are tested, “more than 1,000 variants in the BRCA1 and BRCA2 genes are known to increase cancer risk.” The limitations of each health result are spelt out in clear bullet points.
“Integrity is foundational to what we do,” says Dr L Okey Onyejekwe Jr, vice president of healthcare operations and medical affairs at 23andMe. “That is why we reserve ourselves from going further than where science allows us to go.”
He says that for a narrow range of disorders a genetic test delivers highly comprehensive information. These are “single gene” disorders, such as alpha-1 antitrypsin and haemochromatosis. But these “single gene, single disease” examples are rare. For other conditions, the company emphasises the complexity of the job in hand. “For breast cancer, the test is not conclusive,” says Onyejekwe Jr. “We don’t claim that it is. But it expands coverage beyond what any traditional health care is covering. So there is value in that.”
23andMe holds back on publishing a range of potential genetics links on the app as the medical research is under the confidence threshold. The company also provides a treasure trove of information, including links to original research, to help consumers understand the nuances of their results.
Other providers are more adventurous. For example, epigenetics is the science of how DNA is expressed. Providers such as Bio-Synergy claim to be able to calculate your biological age compared to your chronological age via epigenetic testing. “It’s methylation,” says Brown, referring to the epigenetic mechanism that regulates gene expression. “And changes in methylation are up to 97% accurate at predicting your biological age, especially in younger people.” Smoking, for example, is visible at the epigenetic level. So it’s an informative, scientifically valid service.
The founder of Bio-Synergy, Daniel Herman, is confident his DNA and epigenetic service passes the threshold of reliability. “We demand a minimum of five peer-reviewed published studies before we incorporate the science,” says Herman, noting that the company’s head of nutrigenomics, James Brown, has a PhD, while it also works with other parties on the data.
Providers push different interpretations depending on their reading of the science. Bio-Synergy, for example, claims to be able to detect the likelihood of vitamin deficiencies due to DNA, and sells vitamin drips to counteract this. This is more speculative, says Brown. “There are rare metabolic abnormalities,” she says, “but those are very rare and evident throughout childhood.” Bio-Synergy points to research to support its claims.
Genetics is a complex area. Interpreting results beyond a narrow range of disorders takes medical knowledge. Mercifully, the main providers are keen to stress this, and if anything err on the side of caution.
The real gain is for science as a whole. As anonymised DNA data is shared, along with survey data collected by test providers, scientists are reaping the benefits.
“I have used research data from 23andMe,” says Brown. “They share collected genetic testing with researchers and I’ve benefited from this.” Brown says the company’s numbers “blew out of the water the numbers from other sources. Genetics is about numbers, it’s about probabilities. We need bigger and bigger numbers. And that’s what we get through resources such as 23andMe.”
For the individual, the results are fascinating. But the bigger payoff is for scientists. Massive datasets will unlock the secrets of the genome. Over time, the insights will get better and better.
DNA tests are thus the future of healthcare, just not quite in the way the consumer may envisage.