Over the counter genetic tests that claim to predict the risk of illnesses such as heart disease and cancer ‘miss nine in ten cases’

Genetic tests that claim to predict the risk of diseases such as heart disease and cancer miss nine out of 10 cases, a major study has found.

Analysis of polygenic risk scores – which use genetic variations to estimate a person’s chances of health problems – found they ‘performed poorly’ at identifying cases.

One in 20 also resulted in a false positive result (when someone is wrongly diagnosed as having a disease), causing concern and potentially requiring unnecessary tests and treatments.

Negative results could also be ‘falsely reassuring’ for patients, doctors warned.

The commercially available tests are often heralded as a breakthrough that could transform the prediction and prevention of common diseases.

Over-the-counter genetic tests have been found to perform poorly in identifying cases of heart disease and cancer

But in a review of 926 polygenic risk scores for 310 diseases, researchers at University College London found that they typically identified only 11 percent of individuals who subsequently developed disease.

For breast cancer, they identified only 10 percent of final cases, along with 12 percent of cases of coronary artery disease, a leading cause of heart attacks and strokes.

At the same time, they incorrectly suggested that 5 percent of people would develop a disease who would not, which could have enormous consequences for healthcare.

Experts warned that the tests, if used widely – for example as part of a national screening program – would result in more false than true positive predictions.

Professor Aroon Hingorani, from the UCL Institute of Cardiovascular Science, who led the study, said strong claims have been made about the potential of polygenic risk scores in medicine.

“Our investigation shows that this is not justified,” he says.

‘We found that polygenic risk scores, when held to the same standards as those for other tests in medicine, performed poorly for predicting and screening for a range of common diseases.

‘Based on the evidence we looked at, we could see no place for these tests in the screening.

‘The most important thing with many of these conditions, such as heart disease, is that if we have safe and effective preventive treatments, such as diet and lifestyle, as well as statins and blood pressure lowering drugs, we can achieve more by using them more widely.’ The researchers also examined how polygenic risk scores would perform if used alongside conventional screening methods.

They found that if used in addition to conventional risk factors, several thousand people would need to have a polygenic risk score performed to guide statin prescriptions to prevent an additional heart attack or stroke.

Using age alone as a guide to prescribing statins would be simpler and more effective at preventing heart attacks and strokes without the need for genetic testing, they said.

Adding these risk scores as a first-stage screening to determine who should be prioritized for mammography would miss most women who later develop breast cancer.

According to the findings published in BMJ Medicine, it would also produce many false positives, which would increase pressure on healthcare systems.

Co-author Professor Sir Nicholas Wald (UCL Institute of Health Informatics) said: ‘It has been suggested that polygenic risk scores could be introduced early on to help prevent breast cancer and heart disease, but in the examples we looked at, we found we found that the scores contributed little or no health benefit, while increasing costs and complexity.’

Dr. Jasmine Gratton, from the UCL Institute of Cardiovascular Science, is available for patients and companies to buy online and said polygenic risk scores have increased in popularity.

She said they “seem attractive because genotyping is now cheap, is the same for all diseases and is only done once because a person’s genotype does not change.

“However, these characteristics are not relevant if the test is not useful,” she added.

However, Professor Michael Inouye and Assistant Professor Sam Lambert of the University of Cambridge, lead authors of the PGS catalog looked at in the study, defended the tests.

They said they had “potential utility in many different clinical use cases” and other studies are using the system “in more flexible ways.”

They said: ‘The current paper generally takes a narrow view of how polygenic scores can be used.’