Too many people are relying on over-the-counter genetic tests which can “easily be misinterpreted” and should not be relied on solely to make health decisions, experts have said.
DNA tests sold in shops and online, known as direct to consumer (DTC) tests, promise insights into ancestry, disease risks, and information on personality, athletic ability, and child talent.
Although people expect these tests to provide clear-cut answers about their future health, interpretation of the data is “complex and context-dependent”.
Anneke Lucassen, professor of clinical genetics at the University of Southampton, and colleagues warn in the BMJ that false positives – where results indicate a person has a high genetic risk of a disease or condition when they do not – are common, while false negatives may “reassure” at-risk people that they have little to worry about. And most people with apparent “positive” results will not go on to develop the related condition.
The experts write: “Genetic data are complicated, and can easily be misinterpreted. DTC genetic tests are sold as providing answers, and patients may understandably expect that their results will be clearly predictive of future health. These expectations, driven by marketing and media coverage, leave people at risk of over-interpreting results from DTC genetic testing.”
Roll-out
Earlier this year, Matt Hancock called for predictive genetic tests for common cancers and heart disease to be rolled out on the NHS without delay. The health secretary revealed he had taken a commercial genetic test that showed he was at heightened risk of developing prostate cancer, saying he was shocked by the result.
However, scientists said the tests, which have been largely developed using genetic data from white Europeans, give less accurate results for people from different ethnic backgrounds.
The BMJ article aims to provide advice to clinicians who are approached by patients concerned about their DTC tests results. They advise doctors to put the results in context for their patients, discuss possible sources of error and, if appropriate, shift the conversation from genetic risk to lifestyle changes that could help to reduce the likelihood of future disease.
If a patient is concerned about a “bad news” test result, they should be offered a genetics appointment if they also display symptoms that may indicate the person has the condition in question.
Regardless of any “reassuring” results, GPs are urged to refer anyone with a medical or family history who they would otherwise offer a genetics referral.
The experts said: “The assumption that DTC genetic testing empowers people to reduce their future disease risk is undermined by evidence that suggests that learning about genetic predisposition to particular diseases rarely leads to sustained lifestyle change.”
Professor Helen Stokes-Lampard, chair of the Royal College of GPs, said genomic sequencing data has “huge potential” but that healthcare professionals and the public should exercise caution.
She said: “Genetic testing shouldn’t simply be done to satisfy a patient’s curiosity about their health as the results could have very real implications. But as it stands, we don’t have the expertise to interpret them in a sophisticated enough way to be of great benefit for our patients.”
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