An online test can predict if you’re at high risk for prediabetes, but does that mean you should go see your doctor?

In this day and age, personalized medical technology makes it easier than ever to learn about our own health and how our body is doing without needing to see a doctor.

From wearable fitness trackers to shopping metrics that can predict when you’re pregnant, smart tech and big data are working together to teach us more about ourselves than we ever knew before.

And while it’s cool to know how many more kilometers we have to walk before our next “Pokémon Go” egg hatches, it’s also useful to directly apply this information to improving health outcomes on a national level.

That philosophy is at the center of a debate over the effectiveness of screening tests to assess people’s risk of prediabetes.

And that debate was revived this week with a published study that estimated that almost 60 percent of people in the United States over the age of 40 are at high risk for developing prediabetes.

Read more: Five signs of aging that could be diabetes in disguise »

The Centers for Disease Control and Prevention (CDC), American Diabetes Association (ADA), and the American Medical Association (AMA) teamed up to produce a free online screening test to predict whether someone might be at higher risk for prediabetes based on seven questions.

The online test examines age (1 to 3 points), sex (1 point), gestational diabetes (1 point), family history (1 point), blood pressure (1 point), physical activity (1 point), and weight (1 to 3 points).

A score of 5 or higher is considered to be high risk. The website recommends that people at high risk see their doctor and ask to get a blood test for prediabetes.

Prediabetes, currently defined by the ADA to be a fasting blood sugar level of 100 milligrams per deciliter, occurs when someone has a blood sugar level that is higher than normal but not so high that it qualifies as type 2 diabetes. Although many people with prediabetes will go on to develop type 2 diabetes, many will not.

This makes prediabetes a useful, but not perfect, categorization to use as a health predictor for type 2 diabetes prevention efforts.

A more accurate measurement method than simply elevated blood sugar levels is a sugar tolerance test, in which a person consumes a specific dose of sugar in the lab and then has their blood sugar levels tested to see how long it takes for their levels to return to normal.

This test specifically measures how hard the pancreas has to work to generate sugar-busting insulin to handle the incoming rush of sugar. It’s considered a pretty good predictor of how soon the pancreas will start giving out for good.

People whose prediabetes is detected by high sugar tolerance on this test are clear candidates for diabetes prevention efforts, recent research has found. Lifestyle modifications such as diet and exercise, as well as medications such as metformin to help sugar regulation, have been shown to reduce the number of people whose prediabetes will become type 2 diabetes. By reducing the burden on the pancreas, it has a chance to heal.

More than 8 percent of people in the United States have type 2 diabetes, in which the blood becomes so overloaded with sugar that it begins damaging the bloodstream and all the tissues it normally supplies with oxygen and nutrients.

In addition to dramatically raising the risk of heart attack and stroke, the disease begins destroying the tiny blood vessels called capillaries that feed the most sensitive parts of the body: the fingers and toes, the eyes, pain detecting nerves, and even the brain.

As the sugar damages these fragile capillaries, the tissues they serve begin to die. The result can be gangrene leading to finger or foot amputation, blindness, incurable neuropathic pain, or even dementia.

This makes any possible effort that would actually prevent or delay the onset of type 2 diabetes well worth the effort and investment. High sugar tolerance is one such predictor of who to hurry into preventative care. And, the ADA says, only 1 in 9 people with prediabetes knows that they have it.

Not mentioned in the online screening is one other major risk factor for prediabetes: polycystic ovarian syndrome (PCOS). Women with PCOS are at substantially higher risk for prediabetes, and might benefit from additional screening and preventative treatment even in the absence of other risk factors.

Nonetheless, the online risk assessment screening test could prove to be quintessential in offering a cheap and easily distributed way to determine which people might benefit from additional testing by their doctor.

Read more: Campaign launched to screen for prediabetes »

However, elevated blood sugar levels alone, in the absence of sugar tolerance, aren’t so clear a predictor of either a future of type 2 diabetes or the need to intervene with drugs or all kale diets to prevent it.

The picture gets even muddier when taking into consideration that the definition of prediabetes isn’t set in stone.

The World Health Organization (WHO) does not use the word “prediabetes,” but defines “impaired fasting hyperglycemia” as having a fasting blood sugar level of 110 mg/dL, which the ADA agreed with until it lowered that number to 100 mg/dL in 2003.

This change in definition effectively increased the number of people described as prediabetic by millions overnight.

Other changes in the ADA’s definition of prediabetes have broadened its scope so that, today, 86 million Americans age 20 or older would meet criteria for prediabetes.

The practical implications of this screening test began to arise. That’s why Dr. Saeid Shahraz, Ph.D., and his colleagues at Tufts Medical Center, decided to put it through its paces and stress test the screening model.

Shahraz and his team took data from the 2013-2014 National Health and Nutritional Examination Survey (NHANES). It gathered a wide range of health information from 10,175 participants who were intended to be a representative sample of the U.S. general population.

Of those participants, 96 percent had supplied enough information to the original survey that Shahraz’s team could run their information through the prediabetes screening survey and see what the results uncovered.

The results were published Monday in a research letter in JAMA Internal Medicine.

From the prediabetes screening test, researchers estimated that 73 million Americans age 40 or older (58 percent) were at high risk for prediabetes. Among Americans over the age of 60, more than 80 percent were at high risk for prediabetes.

The test that the ADA recommends for those at high risk for prediabetes is the fasting blood glucose (sugar) test, which costs anywhere from $175 to $330 per person. This means that if the average cost per test were $225, it would cost roughly $16 billion to test each of these 73 million people for prediabetes.

“We [would] need to spend enormous resources to reach out to this enormous number of patients and implement effective interventions for them,” explained Shahraz in an interview with Healthline. “While we are not against screening programs for prediabetes, whose effectiveness has not been shown anyway, we focused on our research on the validity of the screening method. If ADA and other fundamental medical organizations decide to actively screen for prediabetes, they need a valid algorithm to identify cases with some reasonable margin of accuracy.”

And there’s the issue at hand. If the ADA is advocating spending billions of dollars on screening, is their cutoff in the right place?

“The definition of prediabetes is arbitrary,” Shahraz pointed out. “This decision is still an issue under debate. There is no evidence to show which threshold is the right one to pick.”

But the threshold, pointed out Dr. Robert Ratner, chief scientific and medical officer of the ADA, in a comment response in Diabetes Carein 2015, has to be somewhere.

“We feel a great deal of attention — perhaps too much — has been paid over the recent past to the fact that [individuals] at the lower ends of the glycemic ranges are at lower risk for progressing to diabetes than the individuals at the higher ends,” he wrote. “We can continue to argue over what the exact diagnostic cut points for each test should be, but the bottom line is that these are categories suggesting increased risk for developing diabetes, and it is inevitable that when you have physiological ranges of a continuous variable, the risks will be lower at the lower ends of the ranges than at the higher ends.”

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Today, even in light of Shahraz’s findings, Ratner upholds the ADA’s prediabetes cutoff and the guidelines in the online screening test.

“We stand by our recommendation,” he told Healthline. “There are 86 million American adults with prediabetes, and almost 90 percent of them don’t know it. And there are 8 million American adults with diabetes who are undiagnosed. With that many people at risk for complications — which can start even before diabetes develops — it’s reasonable for patients and their doctors to be assessing their risk.”

This recommendation, however, is controversial.

“The [online test’s] risk score does nothing to help to improve outcomes,” argued Dr. Rita Redberg, chief editor of JAMA Internal Medicine, and professor of medicine at the University of California, San Francisco, in an interview with Healthline. “I do not recommend this screening. I would suggest instead of getting screened, just work on reducing the risk of ever getting diabetes by making some small changes right away. Weight loss and healthy lifestyle clearly can improve outcomes.”

Redberg explained, “The diabetes prevention programs all have weight loss as a goal. There is no specific outcome related to diabetes. But we know that obesity is a big risk factor for diabetes. The best way to reduce the risk of obesity-related health problems, such as diabetes and prediabetes — whatever that is — is to lose weight, by eating a heart healthy Mediterranean style diet, and increasing physical activity, such as walking, and not smoking.”

Shahraz seems to agree with Redberg.

“First off, they should not worry of being categorized as high risk for prediabetes,” he advised people who have taken the online screening test. “If they have their blood tested, there will be a high chance that they are normal. Even if their fasting sugar turns to be in the prediabetes range, they should take it only as a wake-up call. A good majority of them will not progress toward diabetes. However, they should take lifestyle change recommendations seriously, which are already the right recommendation for all chronic diseases as well as for healthy population.”

At the end of the day, though, Ratner feels that the final decision should lie with medical professionals if someone rates high risk on the online test.

“We advise them to see their doctor about whether they need to have a blood test done,” he said. “It’s still up to the doctor to use his [or] her clinical judgment whether to do further testing.”