A 2-step approach to diagnosing T2DM
An alternative to relying on a single test for T2DM is to use a 2-step approach for screening. The first step is a hemoglobin A1c measurement, which neither requires fasting nor waiting for 2 hours for post–glucose load blood draw. If the hemoglobin A1c result is ≥6.5%, a T2DM diagnosis can be made, with no additional testing. If the hemoglobin A1c result is 5.7% to 6.4%, the person probably has either prediabetes or diabetes and can be offered a 2-hr OGTT to definitively determine if T2DM is the proper diagnosis. If the hemoglobin A1c test is <5.7%, it is unlikely that the person has T2DM or prediabetes at the time of the test. In this situation, the testing could be repeated in 3 years. Using a 2-step approach reduces the number of people who are tested with a 2-hr OGTT and detects more cases of T2DM than a 1-step approach that relies on a hemoglobin A1c measurement alone.
Treatment of prediabetes is warranted in people at high risk for developing diabetes
It is better to prevent diabetes among people with a high risk of diabetes than to treat diabetes once it is established. People with prediabetes who are overweight or obese are at high risk for developing diabetes. Prediabetes is diagnosed by a fasting plasma glucose level of 100 to 125 mg/dL or a hemoglobin A1c measurement of 5.7% to 6.4%.
High-quality randomized clinical trials have definitively demonstrated that, among people at high risk for developing diabetes, lifestyle modification and metformin treatment reduce the risk of developing diabetes. In the Diabetes Prevention Program (DPP) 3,234 people with a high risk of diabetes, mean BMI 34 kg/m2, were randomly assigned to 1 of 3 groups9:
- a control group
- metformin (850 mg twice daily) or
- lifestyle modification that included exercise (moderate intensity exercise for 150 minutes per week and weight loss (7% of body weight using a low-calorie, low-fat diet).
At 2.8 years of follow-up the incidence of diabetes was 11%, 7.8%, and 4.8% per 100 person-years in the people assigned to the control, metformin, and lifestyle modification groups, respectively.9 In the DPP study, compared with the control group, metformin was most effective in decreasing the risk of transitioning to diabetes in people who had a BMI ≥35 kg/m2 (53% reduction in risk) or a BMI from 30 to 35 kg/m2 (16% reduction in risk).9 Metformin was not as effective at preventing the transition to diabetes in people who had a normal BMI or who were overweight (3% reduction).9
In the Finnish Diabetes Prevention Study, 522 obese people with impaired glucose tolerance were randomly assigned to lifestyle modification or a control group. After 4 years, the cumulative incidence of diabetes was 11% and 23% in the lifestyle modification and control groups, respectively.10 A meta-analysis of 23 randomized clinical trials reported that, among people with a high risk of developing diabetes, compared with no intervention (control group), lifestyle modification, including dieting, exercising, and weight loss significantly reduced the risk of developing diabetes (pooled relative risk [RR], 0.78; 95% confidence interval [CI], 0.69‒0.88).5
In clinical practice, offering a patient at high risk for diabetes a suite of options, including5,9,10:
- a formal nutrition consult with the goal of targeting a 7% reduction in weight
- recommending moderate intensity exercise, 150 minutes weekly
- metformin treatment, if the patient is obese
would reduce the patient’s risk of developing diabetes.
Treatment of T2DM is complex
For people with T2DM, a widely recommended treatment goal is to reduce the hemoglobin A1c measurement to ≤7%. Initial treatment includes a comprehensive diabetes self-management education program, weight loss using diet and exercise, and metformin treatment. Metformin may be associated with an increased risk of lactic acidosis, especially in people with renal insufficiency. The US Food and Drug Administration (FDA) recommends against initiating metformin therapy for people with an estimated glomerular filtration rate (eGFR) of 30 to 45 mL/min/1.73 m2. The FDA determined that metformin is contraindicated in people with an eGFR of <30 mL/min/1.73 m2.11 Many people with T2DM will require treatment with multiple pharmacologic agents to achieve a hemoglobin A1c ≤7%. In addition to metformin, pharmacologic agents used to treat T2DM include insulin, sulfonylureas, glucagon-like peptide-1(GLP-1) receptor agonists, a sodium glucose cotransporter (SGLT2) inhibitor, dipeptidyl peptidase-4 (DPP-4) inhibitors, or an alpha-glucosidase inhibitor. Given the complexity of managing T2DM over a lifetime, most individuals with T2DM receive their diabetes care from a primary care clinician or subspecialist in endocrinology.
Experts predict that, within the next 8 years, the prevalence of obesity among adults in the United States will be approximately 50%.12 The US health care system has not been effective in controlling the obesity epidemic. Our failure to control the obesity epidemic will result in an increase in the prevalence of prediabetes and T2DM, leading to a rise in cardiovascular, renal, and eye disease. The diagnosis of prediabetes and diabetes is within the scope of practice of obstetrics and gynecology. The treatment of prediabetes is also within the scope of ObGyns, who have both expertise and familiarity in the diagnosis of gestational diabetes, a form of prediabetes. ●