Millions of people are being needlessly diagnosed with “pre-diabetes,” putting them at risk of receiving “unnecessary” medical treatment and creating “unsustainable burdens” for health care systems, according to a commentary published last week in the journal BMJ.

Written by Dr. Victor Montori, an endocrinologist who specializes in diabetes at the Mayo Clinic in Rochester, and Dr. John Yudkin, an emeritus professor of medicine at University College London, the commentary describes the dubious origins of the “pre-diabetes” label and its unreliable role as a predictor of who will go on to develop diabetes.

“Pre-diabetes is an artificial category with virtually zero clinical relevance,” says Yudkin in a press statement released with the commentary. “There is no proven benefit of giving diabetes treatment drugs to people in this category before they develop diabetes, particularly since many of them would not go on to develop diabetes anyway.”

“Rather than turning healthy people into patients with pre-diabetes, we should use available resources to change the food, education, health, and economic policies that have driven [the obesity and diabetes] epidemic,” he and Montori write in their commentary.

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Yet the “pre-diabetes” label has been attached to one-third of adults in the United States — and half of those living in China.

Changing the terms

As Yudkin and Montori point out, “pre-diabetes” is an umbrella term created in recent years to describe blood sugar levels that are higher than normal but below those that define diabetes.

The term was coined by the American Diabetes Association (ADA), and is widely used in the United States and in global scientific literature. The World Health Organization, however, discourages its use, and urges the medical community to “move away from describing ‘pre-diabetes’ as a separate condition” — a position also shared by the United Kingdom’s National Institute for Health and Care Excellence.

Until the late 1990s, this intermediate category was known as “impaired glucose tolerance.” But testing required a long and laborious process for patients, and the results weren’t always reliable. About 30 percent of people diagnosed with impaired glucose tolerance had normal results when they were re-tested.

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In 1999, WHO officials altered the diagnostic criterion for diabetes to a fasting blood glucose level greater than or equal to 126 milligrams per deciliter (mg/dL). The intermediate category was renamed “impaired fasting glucose” and defined as a fasting blood glucose level of 110-125 mg/dL.

This new test did away with the onerous glucose challenge test. But, in 2003, the ADA, acting on advice from its own expert committee, lowered the intermediate-level threshold to 100 mg/dL. That unilateral action raised concern among public health officials at WHO and elsewhere, who noted that the expanded category roughly doubled the number of people with impaired fasting glucose.

In 2009, a third test was developed. It measures how much of a blood protein called hemoglobin A1c is coated (or glycated) with sugar. The experts at WHO determined that people with levels of A1c greater than 6.5 percent could be diagnosed with diabetes. They also put the threshold for the intermediate category at 6.0 percent.

But a year later, the ADA reduced that threshold to 5.7 percent, “a decision not endorsed by any other group,” note Montori and Yudkin.

Half of all adults in China

What difference do those changes by the ADA make? Their lower thresholds mean that two to three times more people are being told they have impaired blood sugar metabolism — or “pre-diabetes.”

According to recent studies, under the ADA criteria, half of all adults in China would be diagnosed with “pre-diabetes.” That’s half a billion people in that country alone.

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Here in the United States, the ADA criteria means that 35 percent of adults aged 20 and older — 50 percent of adults aged 65 or older — have pre-diabetes. That’s about 86 million people, according to the Centers for Disease Control and Prevention.

Not predictive

But, as Montori and Yudkin explain in depth in their commentary, a pre-diabetes diagnosis offers little value. To begin with, research has shown that half of people identified with “impaired glucose tolerance” and about two-thirds of people identified with “impaired fasting glucose” will not have diabetes 10 years later. And there’s been no evidence to date that borderline A1c levels are any better at predicting who will and who won’t go on to develop diabetes.

Furthermore, treating people with “pre-diabetes” with either lifestyle interventions or drugs has been found, at best, to delay the onset of type 2 diabetes by only a few years rather than prevent it.

“The ADA recommends treating pre-diabetes with metformin, but the majority of people would receive absolutely no benefit,” says Yudkin in the press statement. “There are significant financial, social and emotional costs involved with labeling and treating people in this way. And a range of newer and more expensive drugs are being explored as treatments for ‘pre-diabetes.’ The main beneficiaries of such recommendations would be the drug manufacturers, whose available market suddenly leaps to include significant swathes of the population. This is particularly true in emerging economies such as China and India, where regulating the healthcare market is a significant challenge.”

“Healthy diet and physical activity remain the best ways to prevent and to tackle diabetes,” adds Montori in the press statement. “Unlike drugs, they are associated with incredibly positive effects in other aspects of life. We need to keep making efforts to increase the overall health of the population, by measures involving public policy rather than by labeling large sub-sections of the population as having an illness. This is not a problem to be solved at the bedside or in the doctor’s surgery, but rather by communities committed to the health of their citizens.”

You can read the commentary on the BMJ website. The commentary is part of an ongoing BMJ series on how the expanding definitions of disease and the increasing use of new diagnostic technologies are leading to overdiagnosis.