Blood-testing technology has rocketed ahead in the last five years — the interval of time since it came to light that the former $9 billion startup Theranos Inc. hadn’t actually invented a way to do thousands of lifesaving blood tests using a finger stick. Today, some companies really can do thousands of tests using a single drop of blood.

But that advance hasn’t revolutionized medicine, a blood-testing fantasy promoted as science by Theranos founder Elizabeth Holmes, who went on trial this week for wire fraud and conspiracy. Here’s how she put her vision in a 2014 TED talk: “We see a world in which every person has access to actionable health information at the time it matters. A world in which no one has to say, ‘If only I’d known sooner,’ a world in which no one has to say goodbye too soon.”

This was always a grandiose claim for a blood test, even an accurate and useful one. Measuring biomarkers in a drop of blood just isn’t the same as measuring health or identifying a medical path to happiness.

That would require not just a technological advance, but a much more difficult clinical advance — a leap in doctors’ ability to use blood-testing results to identify and prevent incipient disease. By separating out the clinical from the technical, University of Toronto pathology professor Eleftherios Diamandis has tried to distinguish the specific lies that put Holmes before a jury from the fallacies that still affect medicine.

As for the technical part, he said, a company called Olink can now test a drop of human blood for more than 1,000 substances — some of which might flag disease. Harvard University biologist Steve Elledge developed a test called VirScan during the pandemic and used it to look at dozens of antibodies, not just to SARS-Cov-2 but to other pathogens. These are fantastic tools for scientists trying to understand disease and human biology.

If Theranos had delivered the technical part anywhere near this well, Holmes might not be on trial and the company might be making lots of money. But it probably wouldn’t be doing much to improve human health because the clinical part of the promise was empty.

It’s not that the technical and the clinical will never merge, and there are incremental advances in certain kinds of testing  — especially blood-glucose monitoring to help diabetics stay healthier, and testing for a substance called troponin, which can signal whether someone is suffering from a heart attack.

But for those who aren’t sick, there’s really no evidence, Diamandis said, that doing a slew of random blood tests, without knowing what you’re looking for, will help diagnose or prevent anything.

One of the perils of random testing of healthy people is the danger of false positives followed by harmful, unnecessary treatment. With cancer, he said, this is complicated by the fact that some cancers grow so slowly that they’d never cause any symptoms, so early detection causes harm by leading to pointless, aggressive treatment.

There is, or was, one company that appeared to do an honest job of what Theranos had claimed to be doing. It was called Arivale, and was founded in 2015 by biology superstar Leroy Hood. The service would give people reams of data — not just a blood test for disease-predicting markers but genetic tests and a scan of the friendly human bacteria known as the microbiome.

The company never developed a broad customer base and went out of business in 2019. It may have failed to deliver enough useful information to justify the cost, which, according to the Seattle Times, was about $99 a month. (Though there might still be a market for the part that satisfied customers reported: primarily that they learned they had low vitamin D and high mercury levels, two easy-to-detect problems common in well-to-do sushi-eating office workers.)

Also, a number of companies have sprung up to deliver a cancer-specific version of the Theranos claim: blood tests that detect a range of cancers. CancerSEEK, Galleri and PanSeer offer these non-invasive tests, also called liquid biopsies, which work by picking up fragments of abnormal DNA.

The technology is already used to measure the progression of disease or its recurrence in patients being treated for cancer. But Diamandis, who wrote a review paper on liquid biopsies, says there isn’t enough evidence yet that these should be used to predict cancer in healthy people.

False positives from such tests are likely to outnumber real ones, wrote Gilbert Welch of Brigham and Women’s Hospital, in an August opinion piece for STATnews. He wrote that while the effect on public health could be negative, liquid biopsies could be big money makers if they can get backing from insurance companies and Medicare. “The only thing that is clear to me is that this will cost a lot of money,” he wrote.

So perhaps we should be glad that investors didn’t get what Holmes promised them, because there is big money in selling medicine to the healthy and a big risk of making people less so.

This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Faye Flam is a Bloomberg Opinion columnist and host of the podcast “Follow the Science.” She has written for the Economist, the New York Times, the Washington Post, Psychology Today, Science and other publications.

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