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Podcast Review: The dangers of DIY genetic testing – Science Weekly, The Guardian

28 October 2019
Appeared in BioNews 1021

By 2022 the world's consumer genetic testing market is expected to quadruple to £200 million, according to The Guardian. But while the popularity of DIY genetic testing has undergone huge expansion in recent years, doctors and scientists have called for a crackdown on tests offered by consumer genetics companies such as 23andMe and AncestryDNA.

Why is this the case? Surely, such means of testing opens up new possibilities to determine future health risks to individuals, and empower them to take action?

To find out more, I listened to an October edition of The Guardian's Science Weekly podcast, where journalist Hannah Devlin and selected experts discussed what dangers do-it-yourself (DIY) genetic tests pose, and why many professionals are unsettled by them.

The episode starts with a baffling statistic, that 'according to a recent piece in the MIT Technology Review, by the start of this year more than 26 million have taken a direct-to-consumer test'. I was intrigued by why individuals would want to know more about their genome, and what they do with their results.

Anneke Lucassen, professor of clinical genetics at the University of Southampton, and an honorary consultant at Wessex Clinical Genetics Service, provides some insight. She reflects on the experience of one of her patients, who delved into her genetics via an ancestry test that had been given to her as a gift.

'She was very interested to know where her father might have come from. And then she decided to send that kit off to other companies to see what else might be in her raw genetic data that they provided as a zip file. And that, to her surprise, came back with an alteration in the BRCA1 gene,' said Professor Lucassen.

Mutations in BRCA genes convey a high risk of breast and ovarian cancers. Professor Lucassen continued: 'She was very concerned about that…and was interested in having her breasts and ovaries removed as a preventative measure.'

The operation was only cancelled when the NHS, which uses more powerful genotyping tools, showed the result was a false positive. Despite the revelation, Professor Lucassen said the patient asked: 'Can I have the surgery anyway, just to be on the safe side?'

How one wrong result had such great impact shocked me, and I thought back to the 26 million who have taken one of these tests; I doubted whether it was an isolated case. Indeed, Professor Lucassen revealed she is aware of around 10 cases where patients were referred to genetics services after having tested positive for BRCA or bowel cancer mutations, which were later shown to be false by the NHS.

Why professionals are speaking out about DIY genetic testing is becoming very clear. But why are such catastrophic mistakes being made? Part of the problem is that the technology used by direct-to-consumer companies, which looks at SNPs (single nucleotide polymorphisms), is not designed to give accurate results for rare mutations.

'SNPs are single points of variation throughout the genetic code…they are good at identifying common variation within a population, but bad at accurately identifying a rare variation,' Professor Lucassen said. Consequently, a test may give a false positive.

A recent analysis emphasised just how inaccurate these tests can be. The study, conducted at the University of Exeter, found that a commercial DNA test used by direct-to-consumer companies was correct just 16 percent of the time when it detected a rare pathogenic BRCA mutation. It also failed to identify more than half of individuals with actual BRCA mutations in a UK BioBank dataset of 49,908 individuals.

Even if raw data is correct, secondary companies may provide further information at the request of an individual. This, however, may lead to misinterpretation.

It was also disturbing to hear the psychological impact inflicted on individuals, who aren't necessarily reassured because they believe results have been provided through a highly technical and accurate route. 

Genetic counsellors are also left to deal with alarming or confusing results. One patient, according to Dr Amy Taylor, lead consultant genetic counsellor at Addenbrooke's hospital in Cambridge, sought re-analysis after their test results that had originally shown five or six pathogenic variants in BRCA1 and BRCA2. 'If true, the patient probably wouldn't be alive, but the patient didn't know that, and neither did their GP who referred them to us,' Dr Taylor said.

Even if test results are correct, 'it can be difficult to interpret them depending on family history', she said.

Therefore, care must be taken when seeking interpretation, but this is emphasised by 23andMe, which, speaking to Devlin, said: 'We do not advice customers to utilise third party interpretation services, and note the risks of doing so very clearly on our website and within customers' accounts.'

The podcast ends with a few words of advice from the panel, with Professor Lucassen summarising her thoughts in both a humorous and hard-hitting manner: 'If you are interested in using a test, then use it to determine the pedigree of your dog. But even then, take any results with a pinch of salt,' she said.

Overall, this podcast was both intriguing and informative, providing raw perspectives from a number of professionals while keeping scientific jargon to a minimum. Although there is little doubt such tests have the potential to be life-changing, there are still caveats. If, like myself, you are keen to know more, then I would highly recommend setting aside a mere half-hour of your day to indulge in this offering from The Guardian.

SOURCES & REFERENCES
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