Testing your DNA, plus Health Briefs

by Margo White / 26 September, 2013
It may be fun to get a cheap DNA test, but don’t expect it to give much real insight into your health.
23andMe is a high-profile direct-to-consumer online gene-testing service that presents a compelling argument for getting your DNA looked into: “Find out if your children are at risk for inherited conditions, so you can plan for the health of your family.” Or: “By knowing your DNA, you can take steps toward living a healthier life.” All it costs is US$99 and 2.5ml of your spit – but is it really worth it?

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Probably not, says Associate Professor Tony Merriman from the department of biochemistry at the University of Otago. He should know; in his research he looks at the role of genes in various diseases, and he recently co-authored a study that identified a gene that malfunctions in response to sugary drinks, raising the risk of gout. He has had his own DNA tested by 23andMe. It was interesting to discover more about his ancestry, he says, and it was useful for teaching purposes – but it didn’t offer much insight into his health.

As he notes, contrary to popular perception, only a few diseases – such as Huntington’s disease or some forms of breast cancer – can be traced back to deterministic or partly deterministic genes. Most diseases are caused by a constellation of interacting genes, most of which haven’t even been identified yet. Also, disease is generally the result of a combination of genetic information and environment, behaving and interacting in unpredictable ways.

“Take Type 1 diabetes,” says Merriman. “We know through twin studies that about 80% of the reason children get it is because of inherited genes, and the rest is due to environment, but only a small proportion of those genes have been found.” And yet, 23andMe estimated his probability of developing Type 1 diabetes from an analysis of only some of the genes that have been found. “So they tell me that my risk of it is lower, based on analysing eight of the dozens of genetic variants that we know of. But even those dozens of genetic variants only explain a small proportion of the genetic basis for Type 1 diabetes. So that information is effectively useless.”

That 23andMe doesn’t ask for information about a person’s lifestyle also points to the limitations of the accuracy of any risk assessment. “It could tell me that my risk of Type 2 diabetes is lower, so I might think, ‘Great, my genes are going to protect me, I can forget about lifestyle.’ And that would be dangerous.”

At the recent Queenstown Molecular Biology Meeting, Mark Henaghan, dean and professor of law at the University of Otago, drew attention to 23andMe’s consent forms. Reading the legal fine print might make consumers wonder what they’re paying for.

DNA strands. Image/Thinkstock


Consumers are warned “that, for instance, you might learn something about yourself that you didn’t expect”, he says. “That you shouldn’t change your health behaviour solely on the basis of information from 23andMe. That it does not provide medical advice … They have out clauses for everything. ‘We’ll give you this information, but take no responsibility for what it means.’”

This is not to say the science behind the testing isn’t sound, only that it isn’t as straightforward or revealing as the company might have us believe. Interpreting the information in a meaningful way requires considerable expertise, which does not come with the $99 test. “So I think you should only get one if you work closely with a genetic counsellor or a GP who understand genetics, rather than getting one in isolation,” says Henaghan. “Otherwise it could create concerns and issues that you could well do without.”

Merriman agrees. Genetic testing can be useful, and is likely to become more so, but it’s best used cautiously and in relation to specific conditions. “We might get to a point where rheumatoid arthritis genetic tests, for example, might be useful. If, say, a woman in her thirties turns up with early arthritis, rheumatoid arthritis can be difficult to diagnose, and we need to do that as soon as possible, as getting the best treatment early on is really important for long-term outcomes.

“So a genetic test, when they get better, might be very useful – but that’s where we have to go with genetic testing: using it when there is a good reason for it, rather than going fishing for potential problems.”

Health briefs


VIRUS OR BACTERIA?


A blood test developed by Duke Medicine researchers has 90% accuracy at distinguishing between viral and bacterial infections in people with respiratory illnesses. The test detects a specific genetic “signature” that a sick person’s immune system produces in response to a virus, meaning diagnosis could be sped up and the use of antibiotics that don’t work against viral infections could be reduced.

E-READERS FOR DYSLEXIA


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E-readers may make reading easier for some people with dyslexia. A study published in PLOS ONE compared reading speed and comprehension in 100 dyslexic high school students using e-readers with those reading text on paper. Those who struggled most with reading found it easier on an e-reader than on paper, and students with limited visual attention spans had better comprehension using the electronic device. The researchers say having short lines with fewer words may help some dyslexics focus on single words.

MATHS FOR BLOCKHEADS


It’s generally thought playing with blocks helps build the mental scaffolding for maths and science learning, at least in primary schoolers, but research published in Child Development has shown this is true for preschoolers, too. Involving more than 100 three-year-olds of different socio-economic backgrounds, the study found children who were better at copying block structures were also better at early maths. Children from lower-income families were already falling behind in spatial skills by age three, possibly as a result of having less experience with blocks and other skills-building toys.

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