The epidemic of prediabetes is continuing to plague the United States as at least 60 million Americans—one-third of the adult population—meet the criteria for the condition. About 40% of individuals with prediabetes will develop type 2 diabetes in less than 10 years. Unfortunately, a recent CDC report found that only about 7% of individuals with prediabetes have been told that they have it. As diabetes and obesity rates continue to rise, it has become paramount for healthcare providers to make greater efforts to identify prediabetes so that type 2 diabetes, cardiovascular disease (CVD), and their complications can be prevented.

Studies have shown that adults with elevated fasting plasma glucose concentrations and 2-hour plasma glucose levels are at increased risk for developing type 2 diabetes and CVD. Unfortunately, these tests require patients to return to their healthcare providers on a separate day after an overnight fast, which serves as a barrier to test completion. The A1C test is an attractive alternative for identifying adults at high risk for type 2 diabetes. In fact, the International Expert Committee—which represents the American Diabetes Association, the European Association for the Study of Diabetes, and the International Diabetes Federation— recommended adopting the A1C test for the diagnosis of diabetes in 2009.

Exploring Benefits of A1C Testing

Recent studies have strengthened the case for expanding the use of A1C testing to identify high-risk people. They have demonstrated that higher A1C levels in individuals not considered to be diabetic are associated with a higher prevalence of cardiovascular risk factors and greater numbers of incident cardiovascular events.

In the January 2011 issue of the American Journal of Preventive Medicine, my colleagues and I had a study published in which we estimated the composite risks of developing diabetes and CVD for adults with different A1C test results and then compared the risks with those of adults who met the existing criteria for prediabetes, based on fasting and 2-hour glucose testing alone. Among adults who met these existing criteria for prediabetes, the probability for incident type 2 diabetes over 7.5 years was 33.5% and for CVD over 10 years was 10.7%. We also found that using an A1C range of 5.5% to 6.5% alone would identify patients with comparable risks for diabetes (32.4%) and CVD (11.4%). Using a slightly higher cutoff of 5.7% or higher would identify adults with risks of 41.3% for diabetes and 13.3% for CVD. These risks are comparable to adults who participated in past research studies in which intensive lifestyle programs were found to offer a cost-effective approach for preventing type 2 diabetes. A1C-based testing in clinical settings should be considered as another way to identify more adults at high risk of developing type 2 diabetes and CVD.

Improving Prevention Efforts

When evaluating strategies to classify risk for prediabetes, it’s important to consider if these strategies identify people for whom preventive interventions are likely to be cost effective. Health plans are now beginning to pay for prediabetes treatments, giving physicians greater motivation to encourage individuals with prediabetes risk factors to complete screening tests. Since the A1C test is more practical than other testing modalities, it may help physicians perform testing on a much larger scale than ever before.