Based on its review of the evidence, the task force recommends screening for prediabetes and type 2 diabetes in adults ages 35 to 70 who are overweight or obese. The task force also recommends that clinicians offer or refer patients with prediabetes to effective preventive interventions. This is a “B” recommendation, and applies to asymptomatic, nonpregnant adults ages 35 to 70 who are treated in primary care settings.
“Screening and earlier detection can help prevent prediabetes and diabetes from getting worse and leading to other health problems” among these patients, task force member Michael Barry, M.D., said in a press release.
The National Institute of Diabetes and Digestive and Kidney Diseases estimates that just over 30 million people in the United States have diabetes, while about 84 million Americans 18 and older have prediabetes. Over time, diabetes can result in serious health problems, including heart disease, neuropathy, stroke and foot problems. Although several factors impact a person’s chances of developing diabetes, a leading preventable risk factor is being overweight or obese.
The draft recommendation differs slightly from — and, when finalized, will replace — the task force’s October 2015 recommendation statement on screening for abnormal blood glucose and type 2 diabetes mellitus in asymptomatic adults.
In the 2015 recommendation statement, the task force recommended screening for abnormal blood glucose as part of cardiovascular risk assessment in adults ages 40 to 70 who were overweight or obese. The task force also recommended that clinicians offer or refer patients with abnormal blood glucose to intensive behavioral counseling interventions to promote a healthful diet and physical activity.
Although the AAFP supported the 2015 recommendation, the Academy also concluded at the time that there was inadequate evidence to determine whether early detection of abnormal blood glucose or diabetes led to improvements in mortality or cardiovascular morbidity.
To update the 2015 recommendation statement, the USPSTF commissioned a systematic review of the evidence on screening for prediabetes and type 2 diabetes in asymptomatic nonpregnant adults and preventive interventions for those with prediabetes. Specifically, the review focused on the benefits and harms of screening for abnormal blood glucose and type 2 diabetes and the benefits and harms of interventions for screen-detected prediabetes and type 2 diabetes or recently diagnosed type 2 diabetes. A total of 89 publications were included in the review.
The task force reviewed two randomized controlled trials that evaluated the effects of screening for diabetes on health outcomes. Compared with no screening, neither trial found a reduction in all-cause or type-specific mortality with screening over about 10 years of follow-up. In addition, neither trial found statistically significant differences in cardiovascular events, quality of life, nephropathy or neuropathy between screening and control groups. However, the task force noted that data collection was limited to a minority of trial participants for these outcomes.
With regard to interventions, results from one RCT of individuals with screen-detected type 2 diabetes found no difference in health outcomes over five to 10 years when comparing an intensive multifactorial intervention with routine care. However, results from other trials showed that in individuals with recently diagnosed (not screen-detected) diabetes, intensive glucose control interventions with medications such as insulin, metformin or sulfonylureas improved a number of health outcomes, including all-cause mortality, diabetes-related mortality and myocardial infarction over 10 to 20 years.
In obese or overweight individuals with prediabetes, the task force conducted a meta-analysis of 23 trials that compared lifestyle interventions with a control group for delaying or preventing the onset of type 2 diabetes. The meta-analysis indicated that lifestyle interventions that focused on both diet/nutrition and physical activity were associated with a 22% reduction in progression to diabetes. Pooled analyses of other trials also indicated that lifestyle interventions were associated with reductions in weight, body mass index, systolic blood pressure and diastolic blood pressure, while high-contact lifestyle interventions were associated with reduced triglyceride levels and increased HDL cholesterol levels.
“The task force found there are effective ways to help people who have prediabetes lower their risk of diabetes and improve their overall health,” said family physician Chien-Wen Tseng, M.D., M.P.H., M.S.E.E., another member of the task force. “Clinicians and patients should discuss these benefits and choose the approach that works best for each individual.”
Based on the epidemiologic evidence, the USPSTF made one notable change compared with the 2015 recommendation statement, decreasing the age at which to begin screening for prediabetes and type 2 diabetes to 35 years.
Sarah Coles, M.D., chair of the Academy’s Commission on Health of the Public and Science and an assistant professor in the Department of Family, Community and Preventive Medicine at the University of Arizona College of Medicine – Phoenix Family Medicine Residency, told AAFP News that the new recommendation will have a significant impact on the diagnosis and treatment of prediabetes and diabetes.
“This updated draft statement lowers the screening age to include individuals 35 to 39 years age who are overweight or obese and adds screening for prediabetes, a controversial concept,” Coles said.
“The USPSTF defines prediabetes as an HbA1c level of 5.7% to 6.4% or a glucose level of 140 to 199 mg/dL following a two-hour glucose tolerance test,” she added. “This new recommendation will significantly increase the number of individuals diagnosed and labeled with diabetes and prediabetes.”
Regarding the task force’s recommendation to begin screening at age 35, Coles explained that the goal is to reduce the number of people who will go on to develop diabetes and the complications associated with the disease.
“However,” she added, “it is important to note that there is no demonstrated improvement in mortality, cardiovascular events or other health outcomes in individuals with screen-detected diabetes. For interventions targeting prediabetes, most trials did not have sufficient duration of follow-up or did not show a difference in patient-oriented outcomes. Lifestyle interventions to prevent progression for prediabetes to diabetes are effective in reducing weight, blood pressure and cholesterol and would likely be recommended and beneficial for these individuals, even in the absence of screening.”
Asked how the recommendation will affect the care of patients with prediabetes, Coles said that it should be considered a risk factor for progression to diabetes and suggested a number of interventions.
“These individuals should receive lifestyle intervention counseling, including diet and exercise. Medications such as metformin may reduce the incidence of diabetes in the short term, but longer follow-up studies are needed. When considering interventions, including medications, physicians should look at additional factors such as family history, comorbid conditions, and patients’ values and goals.”
Coles also cautioned FPs about the overall benefits of screening for prediabetes.
“Screening for prediabetes is neither sensitive nor specific and may result in patients receiving an incorrect diagnosis or (being) falsely reassured,” said Coles. “The sensitivity of a single A1c measurement for prediabetes is 49% and the specificity is 79%. The USPSTF recommends that the diagnosis of prediabetes be confirmed with a repeat test before interventions are started. Without evidence of patient-oriented benefits of screening for prediabetes, physicians should be cautious when screening and discuss risks and benefits carefully with their patients. Further research is needed to determine if screening in these populations has clinically meaningful benefit.”
Along with the draft recommendation statement, the task force published a new consumer guide on screening for prediabetes and type 2 diabetes.
The USPSTF has also published several additional recommendation statements on the use of behavioral interventions to improve health in individuals who are overweight or obese. In 2018, the task force recommended that clinicians offer or refer adults with a BMI of 30 or higher to intensive, multicomponent behavioral interventions to prevent obesity-related morbidity and mortality in adults, while in 2020, it recommended that clinicians offer or refer adults with cardiovascular disease risk factors to behavioral counseling interventions to promote a healthy diet and physical activity.
The AAFP will review the USPSTF's draft recommendation statement and supporting evidence and will provide comments to the task force. The Academy will also review the recommendation once the task force finalizes its guidance.