Home DNA kits 'falsely warning of high risk of cancer', study warns

The home DNA kits ‘falsely warning of high risk of cancer’: DIY genetic tests are ‘extremely unreliable’ at detecting rare genetic variants, major new study warns

  • Experts warned some women have even booked mastectomy surgery
  • Kits wrongly indicated they had a gene which increased risk of breast cancer
  • Researchers compared kit results with genetic sequencing technology 
  • Consumer DNA tests are booming in popularity and cost around £150 

Trendy DIY genetic tests are falsely telling people they are at a high risk of cancer, a major study has found.

Experts warned that some women have even booked mastectomy surgery after the home kits wrongly indicated they had a gene which significantly increases the risk of breast cancer.

Researchers compared the results of the consumer DNA tests – which are not used by the NHS – with more reliable genetic sequencing technology. The study concluded that tests claiming to detect very rare disease-causing faulty genes are ‘more likely to be wrong than right’.

Consumer DNA tests, which first arrived in Britain in 2014, are booming in popularity and can be ordered online at a cost of around £150.

Experts warned that some women have even booked mastectomy surgery after the home kits wrongly indicated they had a gene which significantly increases the risk of breast cancer (file image)

The tests are sent directly to the buyer’s home, where they swab their cheek and send a sample off to a laboratory for analysis.

The DNA is analysed for rare variations such as mutated BRCA genes – famously carried by US actress Angelina Jolie – that significantly increase the risk of breast cancer.

But the new study found the technology used in the home tests, called SNP chips, is ‘extremely unreliable’ at detecting rare variants.

In variants which are present in fewer than 1 in 100,000 people, 84 per cent of results were false positives – a rate described as ‘shockingly high’ by study co-author Dr Leigh Jackson.

The Exeter University study was based on data from 49,908 patients in the UK. It compared results of genetic sequencing by SNP chips with results from reliable next-generation technology.

It also looked at a further 21 people who underwent consumer genetic tests. Twenty of these had been wrongly detected with at least one false positive rare disease-causing variant. Study experts said they were motivated to conduct the research after hearing anecdotes of women booking surgery after receiving false positive tests for the faulty BRCA1 gene.

The Exeter University study was based on data from 49,908 patients in the UK. It compared results of genetic sequencing by SNP chips with results from reliable next-generation technology (file image)

Lead author Professor Caroline Wright said: ‘SNP chips are fantastic at detecting common genetic variants, yet we have to recognise that tests that perform well in one scenario are not necessarily applicable to others. 

‘We’ve confirmed that SNP chips are extremely poor at detecting very rare disease-causing genetic variants, often giving false positive results that can have profound clinical impact.

‘These false results had been used to schedule invasive medical procedures that were both unnecessary and unwarranted.’

In a 2013 operation, Tomb Raider star Miss Jolie, 45, had both breasts removed along with her ovaries and fallopian tubes to reduce her risk after her mother died from ovarian cancer at the age of 56. 

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