EVANSTON, ILL. — A heart scan that millions of Americans have been paying to have, on the quiet confidence that it is telling them something, may, for most of them, be telling them nothing new, and the finding, which came out of a decade-long study of more than 6,000 adults, is the kind of result the medical world has been, by its own account, waiting for with a mixture of relief and mild professional embarrassment.

The scans in question are the coronary calcium scan, a quick, inexpensive CT that measures how much calcium has built up in the arteries, a number that has become, in the past decade, something between a preventive tool and a consumer product, the sort of thing a person does at a medical spa between a facial and a “wellness consult,” and for which, in the new JAMA study, the added value was, overall, small.

That is the part the headlines will get wrong, which is to say the part the headlines will get right but in a way that makes the finding sound like a failure, when it is, in the account of the researchers, a clarification.

The scans, the study found, are not useless. They are, in fact, most useful in the one situation in which a person is least likely to have gotten them in the first place: when the standard risk calculator, called PREVENT, has already placed a patient in the genuinely ambiguous middle. In that borderline zone, the calcium number, per the Northwestern team, does real work. Everywhere else, it mostly confirms what the calculator already suspected.

"The scan is not the problem. The scan is the *most popular* problem. There's a difference, and the difference is a business model."

The researchers, to their credit, did not spend the study’s conclusion trying to talk the test out of existence. They spent it, instead, talking it into its lane, which is a rarer thing in medicine and, by the account of a cardiologist who read the paper in one sitting, “more useful than any scan I’ve ever had, because it’s the only one that tells you when not to have it.”

What the finding does not do, and what the industry has, quietly, been hoping it won’t do, is settle the question of who, exactly, is the scan for. The answer, as the study frames it, is a smaller and more specific group than the one that has, in practice, been lining up for it, which is a number the researchers did not publish, but which a single hospital billing office, which has, per one insider, “seen the trend,” described as “a lot fewer than the lobby.”

THE SCAN, AS THE STUDY FINDS

  • Study: more than 6,000 adults, followed for 10 years.
  • Overall added value over the PREVENT calculator: small.
  • Where it adds the most value: the borderline / intermediate-risk zone.
  • Where it adds the least: the low and the high ends, where you already know.
  • What it is, in practice, mostly used for: confirming what you came in expecting.
  • What the researchers recommend: the narrower, more targeted version of the above.

At press time, the medical association that promotes preventive screening had issued a statement describing the study as “nuanced,” and the wellness industry that sells the scan had issued a statement describing the study as “nuanced,” and the two statements, which are, at this point, the same statement, will be, by the time they are printed, the study’s most accurate summary, because the scan is not going away, it is simply going to have, for the first time, a reason, and that, in the medical world, is what “evidence-based” has always been, in the direction the evidence actually points.