22 July 2019

Shaoni Bhattacharya By

Appeared in BioNews 1007

Geneticists in the UK have been speaking out against direct-to-consumer DNA testing after concerns over false-positive results.

NHS doctors are seeing an influx of patients following concerning or confusing DNA results, according to clinical geneticist Professor Anneke Lucassen at the University of Southampton.

'The NHS is incredibly irritated by these results because [in the case of BRCA] they're more often wrong than right,' Professor Lucassen who is also chair of the British Society for Genetic Medicine, said in an article in the Guardian newspaper.

She added that it was 'terrifying' that one of her patients had planned irreversible breast surgery on this basis.

Dr Jan Cobben, a clinical genetics consultant at Northwick Park hospital in London, said he had had cases where positive tests for mutations linked to deafness in parents had led them to fears over their children's health. In one case, the hospital repeated the test and found there was no genetic abnormality.

'I'm not saying ban these tests, but they need more regulating,' said Professor Lucassen.

A new – and as-yet not peer-reviewed – study raises similar concerns over the value of genomic testing for very rare pathogenic mutations. The study, published on the preprint server bioRxiv, suggests that genomic analysis using SNP-chips may be unreliable for rare mutations such as those in the BRCA genes associated with breast cancer risk.

The research, led by Dr Caroline Wright at Exeter University, looked at the accuracy of SNP-chips used in genomic analyses for almost 50,000 people recruited to the UK BioBank. The team focused on rare genetic variants in BRCA1 and BRCA2.

'Our study confirms that SNP-chips are highly inaccurate for genotyping rare and clinically-actionable variants,' the study concluded. It added that the SNP-chips 'should not be used to guide health decisions without validation'.

However, genetic genealogist Debbie Kennett noted that most consumer genetic companies use a different SNP-chip to the one used in the study. 'It might therefore be misleading to extrapolate from these results to consumer genetic tests,' she commented on bioRxiv. She added that it would be interesting to replicate the study with the Illumina chip which most commercial companies use.

Dr Wright responded: '…this is definitely something we would like to investigate if we can find the right dataset…'

Major direct-to-consumer testing companies provide genetic analyses restricted to only a few health conditions. For example, last year 23andMe gained US approval for a genetic test for three of the 1000 or so mutations in BRCA1 and BRCA2 associated with increased cancer risk (see BioNews 941).

The Guardian article suggested that issues can arise when raw genetic data downloaded from such consumer tests are processed by third-party companies. It noted that: 'Although these companies normally state that any findings should not be treated as a medical diagnosis, consumers – and even doctors – may be unaware of just how unreliable such results can be.'

A spokeswoman for 23andMe told the newspaper: 'There is a distinction between the validated variants we report on in our … reports and the raw, unvalidated data customers may choose to download on their own. We do not advise customers to utilise third-party interpretation services and note the risks of doing so very clearly on our website and within customers’ 23andMe accounts.'