Since the option of using A1C (a measure of long-term blood glucose control) to diagnose diabetes was introduced over a decade ago, there may have been fewer diabetes diagnoses than using only older methods of diagnosing diabetes would have produced — meaning that many people may not be getting the treatment they need, according to a new study published in the journal The Lancet Regional Health – Europe.
As noted in an article on the study at Medscape, the American Diabetes Association first issued guidance on using A1C as a diagnostic tool in 2010, with a value of 6.5% or higher used to indicate diabetes. The World Health Organization (WHO) followed suit in 2011, and it is now common around the world for A1C to be used to diagnose diabetes. Before 2010, guidelines for diagnosing diabetes included two methods that are still recommended today — a fasting blood glucose test or an oral glucose tolerance test (OGTT). A fasting blood glucose level of 99 mg/dl or below is considered normal, a level of 100-125 mg/dl indicates prediabetes, and a level of 126 mg/dl or higher indicates diabetes. An oral glucose tolerance test involves drinking a solution containing glucose, then having your blood glucose measured at different intervals afterward. After two hours, a glucose level of 140 mg/dl or below is considered normal, a level of 140-199 mg/dl indicates prediabetes, and a level of 200 mg/dl or higher indicates diabetes.
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The latest study looked at changes in how many people were diagnosed with diabetes in Denmark over a 24-year period, from 1995 to 2018 — both before and after guidelines included A1C as an option for diagnosing diabetes. There were 415,553 new diabetes diagnoses over the study period, and the researchers used these participants’ data to calculate an age-standardized rate of diabetes diagnosis. It’s important to control for age in a study like this because older people are more likely to develop diabetes, and the age distribution of participants wasn’t exactly the same from year to year.
Diabetes diagnoses decreased after A1C introduced as diagnostic option
The researchers found that from 1995 until A1C was introduced as a diagnosis option in Denmark in 2012, the age-standardized rate of diabetes diagnosis more than doubled — from 193 to 396 per 100,000 people, representing an annual increase of 4.1% over this period. But from 2012 through 2018, the rate of diabetes diagnosis went down to 253 per 100,000 people, representing an annual decrease of 5.7% over this period. Medical records showed that this decrease in diagnoses was, in fact, driven by fewer people starting treatment for diabetes after receiving an A1C test result below 6.5% without any prior A1C testing. Before A1C was adopted as a test for diagnosing diabetes, many doctors likely would have ordered another test for at least some of these people — tests that might have resulted in a diabetes diagnosis and starting treatment for diabetes.
What’s more, the researchers found that there was a change in the trend for diabetes-related deaths at about the same time as A1C was recommended as a diagnostic test. Between the two time spans of 1995-1997 and 2010-2012, the rate of diabetes deaths dropped from 69 to 38 per 1,000 person-years. But then the rate of diabetes deaths increased again to reach 48 per 1,000 person-years in 2016-2018. While this could be a coincidence and doesn’t prove that changes in how diabetes was diagnosed led to more diabetes-related deaths, it’s also possible that delays in diagnosing diabetes and starting treatment did in fact lead to more deaths.
Despite this single study, there isn’t much evidence right now that using A1C as a diagnostic test for diabetes has had harmful effects. But further studies on this topic — especially ones that compare different test results at the point of a diabetes diagnosis — could lead medical associations to reevaluate their guidelines if it turns out that A1C does, in fact, lead to fewer diagnoses under current guidelines than other tests would.
Want to learn more about A1C? Read “How to Lower A1C Levels Naturally,” “How to Lower Your A1C Levels: More Steps You Can Take” and “HbA1c: What It Is and Why It Matters.”
