U.S. Preventive Services Task Force

Screening for Abnormal Blood Glucose and Type 2 Diabetes Mellitus: Recommendation Statement ▲ See related article on Summary of Recommendation and Approximately 15% to 30% of these persons page 103. Evidence will develop type 2 diabetes within 5 years if As published by the U.S. The USPSTF recommends screening for they do not implement lifestyle changes to Preventive Services Task abnormal blood glucose as part of cardio- improve their health.1 Force. vascular risk assessment in adults aged 40 Modifiable risk factors for abnormal glu- This summary is one in a to 70 years who are overweight or obese. cose metabolism (manifested as either dia- series excerpted from the Recommendation State- Clinicians should offer or refer patients with betes or abnormal glucose levels below the ments released by the abnormal blood glucose to intensive behav- threshold for diabetes) include overweight USPSTF. These statements ioral counseling interventions to promote a and obesity or a high percentage of abdomi- address preventive health healthful diet and physical activity (Table 1). nal fat, physical inactivity, and smoking. services for use in primary care clinical settings, B recommendation. Abnormal glucose metabolism is also fre- including screening tests, quently associated with other cardiovascu- counseling, and preventive Rationale lar risk factors, such as hyperlipidemia and medications. IMPORTANCE hypertension. The complete version of Cardiovascular disease (CVD) is the lead- Given the increasing prevalence of abnor- this statement, includ- ing cause of death in the United States, and mal glucose metabolism in the U.S. popula- ing supporting scientific evidence, evidence tables, nearly one-quarter of deaths caused by CVD tion, the USPSTF sought to examine the grading system, members are considered to be preventable. Modifiable benefits and harms of screening for IFG, of the USPSTF at the time cardiovascular risk factors include abnormal IGT, and type 2 diabetes. this recommendation was blood glucose, hypertension, hyperlipidemia finalized, and references, or dyslipidemia, smoking, overweight and BENEFITS OF EARLY DETECTION AND is available on the USPSTF TREATMENT website at http://www. obesity, physical inactivity, and an unhealthy uspreventiveservices diet. Type 2 diabetes mellitus is a metabolic The USPSTF found inadequate direct evi- taskforce.org/. disorder characterized by insulin resistance dence that measuring blood glucose leads to This series is coordinated and relative insulin deficiency, resulting in improvements in mortality or cardiovascular by Sumi Sexton, MD, hyperglycemia. Type 2 diabetes typically morbidity. Associate Deputy Editor. develops slowly, and progression from nor- The USPSTF previously found adequate A collection of USPSTF mal blood glucose to glucose abnormalities evidence that intensive behavioral counsel- recommendation state- that meet generally accepted criteria for dia- ing interventions for persons at increased ments published in AFP is available at http://www. betes (Table 2) may take a decade or longer. risk for CVD have moderate benefits in aafp.org/afp/uspstf. Glucose abnormalities that do not meet the lowering CVD risk. Populations in which criteria for diabetes include impaired fasting these benefits have been shown include per- glucose (IFG), an impaired response to oral sons who are obese or overweight and have glucose intake (impaired glucose tolerance hypertension, hyperlipidemia or dyslipid- [IGT]), or an increased average blood glu- emia, and/or IFG or IGT. Benefits of behav- cose level as evidenced by increased levels of ioral interventions include reductions in hemoglobin A1C (HbA1C). Abnormal glu- blood pressure, glucose and lipid levels, and cose metabolism is a risk factor for CVD and, obesity and an increase in physical activity. in some individuals, may progress to meet Studies that specifically treat persons who the threshold for the diagnosis of diabetes. have IFG or IGT with intensive lifestyle According to national data estimates from interventions to prevent the development 2012, approximately 86 million Americans of diabetes consistently show a moderate aged 20 years or older have IFG or IGT.1 benefit in reducing progression to diabetes.

January 15, 2016 ◆ Volume 93, Number 2 www.aafp.org/afp American Family Physician 132A USPSTF

Lifestyle interventions have greater effects or diabetes and implementing intensive life- on reducing progression to diabetes than style interventions for persons found to have metformin or other medications. abnormal blood glucose.

HARMS OF EARLY DETECTION AND Clinical Considerations TREATMENT PATIENT POPULATION UNDER The USPSTF found that measuring blood CONSIDERATION glucose is associated with short-term anxiety This recommendation applies to adults aged but not long-term psychological harms. The 40 to 70 years seen in primary care settings USPSTF found adequate evidence that the who do not have symptoms of diabetes and harms of lifestyle interventions to reduce the are overweight or obese. The target popula- incidence of diabetes are small to none. The tion includes persons who are most likely to harms of drug therapy for the prevention of have glucose abnormalities that are associ- diabetes are small to moderate, depending on ated with increased CVD risk and can be the drug and dosage used. expected to benefit from primary prevention of CVD through risk factor modification. USPSTF ASSESSMENT Persons who have a family history of The USPSTF concludes with moderate cer- diabetes, have a history of gestational dia- tainty that there is a moderate net benefit to betes or polycystic ovarian syndrome, or measuring blood glucose to detect IFG, IGT, are members of certain racial/ethnic groups

Table 1. Screening for Abnormal Blood Glucose and Type 2 Diabetes Mellitus: Clinical Summary of the USPSTF Recommendation

Population Adults aged 40 to 70 years who are overweight or obese

Recommendation Screen for abnormal blood glucose. Offer or refer patients with abnormal blood glucose to intensive behavioral counseling interventions to promote a healthful diet and physical activity. Grade: B

Risk assessment Risk factors for abnormal glucose metabolism include overweight and obesity or a high percentage of abdominal fat, physical inactivity, and smoking. Abnormal glucose metabolism is also frequently associated with other cardiovascular risk factors, such as hyperlipidemia and hypertension.

Screening tests Glucose abnormalities can be detected by measuring hemoglobin A1C or fasting plasma glucose or with an oral glucose tolerance test. Diagnosis of IFG, IGT, or type 2 diabetes should be confirmed with repeated testing (the same test on a different day is the preferred method of confirmation).

Screening interval Evidence on the optimal rescreening interval for adults with an initial normal glucose test is limited. Studies suggest that rescreening every 3 years may be a reasonable approach.

Treatment and Effective behavioral interventions combine counseling on a healthful diet and physical activity and interventions involve multiple contacts over extended periods. There is insufficient evidence that medications have the same benefits as behavioral interventions.

Balance of benefits The overall benefit of screening for IFG, IGT, and diabetes and implementing intensive lifestyle and harms interventions is moderate.

Other relevant USPSTF The USPSTF recommends screening and appropriate interventions for modifiable risk factors for recommendations cardiovascular events (overweight and obesity, physical inactivity, abnormal lipid levels, high blood pressure, and smoking). These recommendations are available on the USPSTF Web site (http://www. uspreventiveservicestaskforce.org).

NOTE: For a summary of the evidence systematically reviewed in making this recommendation, the full recommendation statement, and supporting documents, go to http://www.uspreventiveservicestaskforce.org/. IFG = impaired fasting glucose; IGT = impaired glucose tolerance; USPSTF = U.S. Preventive Services Task Force.

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(that is, African Americans, American Indi- ans or Alaskan Natives, Asian Americans, Table 2. Test Values for Normal Glucose Metabolism, Hispanics or Latinos, or Native Hawaiians IFG or IGT, and Type 2 Diabetes* or Pacific Islanders) may be at increased risk for diabetes at a younger age or at a lower Test Normal IFG or IGT Type 2 diabetes body mass index. Clinicians should consider Hemoglobin A1C level, % < 5.7 5.7–6.4 ≥ 6.5 screening earlier in persons with 1 or more Fasting plasma glucose of these characteristics. mmol/L < 5.6 5.6–6.9 ≥ 7.0 SCREENING TESTS mg/dL < 100 100–125 ≥ 126 OGTT results† Glucose abnormalities can be detected by mmol/L 7.8 7.8 –11.0 ≥ 11.1 measuring HbA1C or fasting plasma glu- mg/dL < 140 140–199 ≥ 200 cose or with an oral glucose tolerance test. Table 2 shows test values for normal glucose IFG = impaired fasting glucose; IGT = impaired glucose tolerance; OGTT = oral glucose metabolism, IFG, IGT, and type 2 diabetes. tolerance test. HbA1C is a measure of long-term blood *—From reference 46 (see full recommendation statement). All positive test results glucose concentration and is not affected by should be confirmed with repeated testing. acute changes in glucose levels due to stress †—After 2 hours. or illness. Because HbA1C measurements do not require fasting, they are more conve- nient than using a fasting plasma glucose or diabetes diagnosis than those whose glucose oral glucose tolerance test. The oral glucose levels are closer to normal. tolerance test is done in the morning in a fasting state; blood glucose concentration is TYPE OF INTERVENTION measured 2 hours after ingestion of a 75-g Behavioral interventions that have an effect oral glucose load. on CVD risk and delay or avoid progression The diagnosis of IFG, IGT, or type 2 dia- of glucose abnormalities to type 2 diabetes betes should be confirmed; repeated testing combine counseling on a healthful diet and with the same test on a different day is the physical activity and are intensive, with mul- preferred method of confirmation. tiple contacts over extended periods. The evidence is insufficient to conclude that phar- THRESHOLD FOR BEHAVIORAL macologic interventions have the same multi- INTERVENTIONS factorial benefits (for example, weight loss or Many studies assessed intensive behavioral reductions in glucose levels, blood pressure, interventions for persons at increased CVD and lipid levels) as behavioral interventions. risk, but none report a consistent threshold for intervention among persons with abnor- SCREENING INTERVALS mal blood glucose. Many studies include per- Evidence on the optimal rescreening interval sons with multiple risk factors, and CVD risk for adults with an initial normal glucose increases with the number of risk factors and test result is limited.2 Cohort and modeling glucose level. Perceived readiness for change studies suggest that rescreening every 3 years and access to appropriate interventions will may be a reasonable approach for adults with probably influence treatment recommenda- normal blood glucose levels.3-7 tions. Although direct evidence that prevent- ing a diagnosis of type 2 diabetes results OTHER APPROACHES TO PREVENTION in improved health outcomes is limited, Because overweight and obesity, physi- primary prevention that reduces the chances cal inactivity, abnormal lipid levels, high of a diagnosis may reduce the adverse conse- blood pressure, and smoking are all quences of disease management. Because the modifiable risk factors for cardiovascular average reduction in glucose levels resulting events, the USPSTF recommends screen- from intensive behavioral interventions is ing and appropriate interventions for modest, persons with higher glucose levels these conditions (available at http://www. may be more likely to benefit and avoid a uspreventiveservicestaskforce.org).

January 15, 2016 ◆ Volume 93, Number 2 www.aafp.org/afp American Family Physician 132C USPSTF

The USPSTF recommends screening for This recommendation statement was first published in obesity in adults and offering or referring Ann Intern Med. 2015;163(11):861-868. those with a body mass index of 30 kg/m2 The “Other Considerations,” “Discussion,” “Update of Pre- or greater to intensive, multicomponent vious USPSTF Recommendation,” and “Recommendations of Others” sections of this recommendation statement are behavioral interventions. Although inten- available at http://www.uspreventiveservicestaskforce. sive interventions may not be practical in org/Page/Document/UpdateSummaryFinal/screening-for- many primary care settings, patients can be abnormal-blood-glucose-and-type-2-diabetes. referred from primary care to community- The USPSTF recommendations are independent of the based programs for these interventions. U.S. government. They do not represent the views of the The USPSTF recommends offering or Agency for Healthcare Research and Quality, the U.S. referring adults who are overweight (body Department of Health and Human Services, or the U.S. Public Health Service. mass index > 25 kg/m2) and have addi- tional cardiovascular risk factors to inten- REFERENCES sive behavioral counseling interventions to promote a healthful diet and physical activ- 1. Division of Diabetes Translation, National Center for Chronic Disease Prevention and Health Promotion. ity for CVD prevention. National Diabetes Statistics Report, 2014. Atlanta, The USPSTF recommends screening for Ga.: Centers for Disease Control and Prevention; 2014. lipid disorders in men aged 35 years or older http://www.cdc.gov/diabetes/pubs/statsreport14/ national-diabetes-report-web.pdf. Accessed Septem- and women aged 45 years or older who are ber 18, 2015. at increased risk for coronary heart disease. 2. Selph S, Dana T, Blazina I, Bougatsos C, Patel H, Chou The USPSTF also recommends screening R. Screening for type 2 diabetes mellitus: a systematic for hypertension in adults aged 18 years or review to update the 2008 U.S. Preventive Services Task Force recommendation. Evidence synthesis no. 117. older and that clinicians ask all adults about AHRQ publication no. 13-05190-EF-1. Rockville, Md.: tobacco use and provide tobacco cessation Agency for Healthcare Research and Quality; 2014. interventions to those who use tobacco 3. Takahashi O, Farmer AJ, Shimbo T, Fukui T, Glasziou PP. A1C to detect diabetes in healthy adults: when should products. we recheck? Diabetes Care. 2010;33(9):2016-2017. 4. Kahn R, Alperin P, Eddy D, et al. Age at initiation USEFUL RESOURCES and frequency of screening to detect type 2 diabe- The Community Preventive Services Task tes: a cost-effectiveness analysis [published correc- tion appears in Lancet. 2010;375(9723):1346]. Lancet. Force recommends combined diet and physi- 2010;375(9723):1365-1374. cal activity promotion programs for persons 5. Mortaz S, Wessman C, Duncan R, Gray R, Badawi A. who are at increased risk for type 2 diabetes. Impact of screening and early detection of impaired It found that these programs are effective fasting glucose tolerance and type 2 diabetes in Can- ada: a Markov model simulation. Clinicoecon Outcomes across a range of counseling intensities, set- Res. 2012;4:91-97. tings, and facilitators. Effective programs 6. Waugh N, Scotland G, McNamee P, et al. Screening for commonly include setting a weight loss goal, type 2 diabetes: literature review and economic model- individual or group sessions about diet and ling. Health Technol Assess. 2007;11(17):iii-iv,ix-xi,1-125. 7. Herman WH, Ye W, Griffin SJ, et al. Early detection exercise, meetings with a trained diet or and treatment of type 2 diabetes reduce cardiovas- exercise counselor, or individually tailored cular morbidity and mortality: a simulation of the diet or exercise plans. More information is results of the Anglo-Danish-Dutch Study of Intensive Treatment in People With Screen-Detected Diabetes available at http://www.thecommunityguide. in Primary Care (ADDITION-Europe). Diabetes Care. org/diabetes/combineddietandpa.html. 2015;38(8):1449-1455. ■

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