The UK has been pioneering big databases that permit a new type of disease prediction called a polygenic score—basically, a guesstimate from your genome that you’ll develop a particular disease.

But an effort by the UK’s own health minister to promote the concept this week didn’t go as planned: instead of making the case for the tests, he inadvertently showed why they could be a waste of time and money.

The test: In a speech to the Royal Academy, Matt Hancock, the secretary of state for health and social care, said he’d received the new type of genetic analysis from Genomics PLC, a spinout of Oxford University, and that it calculated his predicted risk of 16 common diseases.

In a promotional video released online, Hancock confided he had a higher than average risk for prostate cancer. "My risk by age 75 is almost 15%,” he worried. The minister immediately booked an appointment with a doctor to get a further blood test.

“The truth is, genomics might have saved my life,” he said.

No it didn’t: All men are at pretty high risk for prostate cancer, and Hancock’s risk was only about 50% greater than average, putting him near the middle of the pack.

Especially if you are 40 years old, as he is, there’s no reason to see a doctor or get a test, according to the National Health Service that Hancock oversees.

“As a result of his misunderstanding, he first suffered unnecessary anxiety and then took up valuable medical time,” Professor David Curtis, from University College London’s Genetics Institute, told the Independent, which accused the minister of an “astonishing level of ignorance.”

How it works: Common diseases aren’t influenced by one gene, but by many. Recently, scientists have gotten good at adding up small genetic effects into an overall score. For a few people at ultra-high risk, these scores could flag potential problems they can try to avoid.

Nearly everyone else is around average, so the scores don’t mean a thing to them. But because they’re so easy to generate from a basic DNA test, companies will be tempted to provide them, even without medical evidence that doing so is helpful.

Earlier this month, we saw 23andMe start telling people about their risk for type 2 diabetes. While proponents say that consumers can understand risk probabilities and everyone should have access to their DNA data, Hancock’s odyssey shows that this may not be the case.

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