Screening for Abnormal Blood Glucose and Type 2 Diabetes Mellitus
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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. 132B American Family Physician www.aafp.org/afp Volume 93, Number 2 ◆ January 15, 2016 USPSTF (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