A group of doctors has called for stricter regulation of consumer genetic testing after patients were wrongly told they were carrying mutations linked to cancer.
Women have been incorrectly informed they have faulty BRCA genes, which convey a high risk of breast and ovarian cancers.
One patient was scheduled for preventive breast-removal surgery but it was called off at the last moment when an NHS laboratory revealed the result to be a false positive.
Doctors said this is placing an increasing burden on GP surgeries and NHS genetics clinics, which are left to deal with the fallout when people receive alarming or confusing results.
Prof Anneke Lucassen, a clinical geneticist at Southampton University and chair of the British Society for Genetic Medicine, told the Guardian it was “terrifying” that one of her patients – and possibly others – had planned irreversible breast surgery on the basis of flawed results.
“I’m not saying ban these tests, but they need more regulating,” she said.
A recent analysis of a genetic testing chip found that for typical disease-causing BRCA mutations a positive result was far more likely to be wrong than correct.
Lucassen said she is personally aware of about 10 cases of patients being referred to genetics services after having tested positive for BRCA or bowel cancer mutations, which were later shown to be glitches when NHS labs conducted more rigorous tests.
Consumer genetics tests offering insights on health and ancestry have surged in popularity in the past few years, with hundreds of thousands of people in the UK thought to have undergone testing.
The major consumer genetics companies, such as 23andMe or AncestryDNA, typically offer just ancestry testing or health readouts restricted to a handful of conditions. However, consumers can download their raw genetic data and send it to third-party companies, which for around £20 provide results and analysis on thousands of genes.
Recent analysis of a commercial DNA chip found that it was correct just 17% of the time when it detected a rare pathogenic BRCA mutation of the kind that substantially increases risk of breast and ovarian cancer. The test was also found to miss more than half of those with actual BRCA mutations, in a dataset is nearly 50,000 individuals.
Caroline Wright, a genomics researcher at Exeter University who led the analysis, said: “At the point where they’re this bad, you have to think about not sharing the data. It can be so damaging to the individual if they find out this completely erroneous information.”
Kwame Iwegbue, CEO of LiveWello, which carries out secondary analysis of DNA data, said the company does not alert customers to the risk of false positive or false negative results because these are “qualities of diagnostic tests”. “
Iwegbue said it was “absolutely” reasonable for NHS clinics to cover the cost of interpreting and validating private genetic tests.
“A direct consequence of access to third-party online tools like LiveWello and access to ubiquitous sources of online medical knowledge is that patients nowadays are empowered and informed,” he told the Guardian. “At the very least the information they acquire from these sources provide talking points for a more rewarding doctor-patient encounter … If the information presented by the patient is in fact wrong, the doctor can use this opportunity to explain the reasons why, and then present the patient with what they consider to be the correct information.”
Greg Lennon, a co-founder of Promethease, said: “When we can, we specifically warn our users of likely miscalls, and in addition, we remind people that reported associations depend on the accuracy of the data.”
A spokeswoman for 23andMe said: “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.”