Screening for Type 2 Diabetes
Diabetes mellitus is a group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action, or both. Type 2 diabetes, the most prevalent form of the disease, is often asymptomatic in its early stages and can remain undiagnosed for many years. Approximately 5.4 million adults in the U.S. have undiagnosed type 2 diabetes. The chronic hyperglycemia of diabetes is associated with long-term damage, dysfunction, and failure of various organs, especially the eyes, kidneys, nerves, heart, and blood vessels. Individuals with undiagnosed type 2 diabetes are at significantly higher risk for coronary heart disease, stroke, and peripheral vascular disease than the nondiabetic population. They also have a greater likelihood of having dyslipidemia, hypertension, and obesity.
Because early detection and prompt treatment may reduce the burden of type 2 diabetes and its complications, screening for diabetes may be appropriate under certain circumstances. This position statement provides recommendations for diabetes screenings performed in physicians' offices and community screening programs.
This position statement does not address screening for type 1 diabetes or gestational diabetes mellitus (GDM). Because of the acute onset of symptoms, most cases of type 1 diabetes are detected soon after symptoms develop. Widespread clinical testing of asymptomatic individuals for the presence of autoantibodies related to type 1 diabetes cannot be recommended at this time as the means to identify persons at risk. Reasons for this include the following: 1) cutoff values for some of the immune marker assays have not been completely established for clinical settings; 2) there is no consensus as to what action should be taken when a positive autoantibody test result is obtained; and 3) because the incidence of type 1 diabetes is low, testing of healthy children will identify only the small number (<0.5%) who at that moment may be "prediabetic." Clinical studies are being conducted to test various methods of preventing type 1 diabetes in high-risk subjects (e.g., siblings of type 1 patients). These studies may uncover an effective means of preventing type 1 diabetes, in which case screening may be appropriate in the future.
For information on screening for GDM, refer to the American Diabetes Association's position statement "Gestational Diabetes Mellitus."
DIABETES PREVALENCE AND RISK FACTORS
The correlation of a risk factor(s) with development of diabetes is never 100%. However, the greater the number of risk factors present in an individual, the greater the chance of that individual developing or having diabetes. Conversely, the chance of finding diabetes in an individual without a risk factor is low. Thus, the likelihood of identifying an asymptomatic individual with diabetes in the general population through random screening is small; however, in high-risk groups the likelihood is much greater.
The risk of developing type 2 diabetes increases with age, obesity, and lack of physical activity. Type 2 diabetes is more common in individuals with a family history of the disease and in members of certain racial/ethnic groups. It occurs more frequently in women with prior GDM and in individuals with hypertension or dyslipidemia. Major risk factors for type 2 diabetes are summarized in Table 1.
GENERAL RECOMMENDATIONS FOR SCREENING BY PHYSICIANS
On the basis of expert opinion, screening of high-risk individuals should be considered at 3-year intervals. The rationale for this interval is that there is little likelihood of an individual developing diabetes and any of the complications of diabetes to a significant degree within 3 years of a negative screening test result.
An FPG level >126 mg/dl (7.0 mmol/l) or a 2-h postload value in the OGTT >200 mg/dl (11.1 mmol/l) are indications for retesting. Either test must be repeated on a different day to confirm a diagnosis. Table 2 presents the diagnostic criteria.
Nondiabetic individuals with an FPG >110 mg/dl (6.1 mmol/l) but <126 mg/dl (7.0 mmol/l) are considered to have impaired fasting glucose (IFG), and those with 2-h values in the OGTT >140 mg/dl (7.8 mmol/l) but <200 mg/dl (11.1 mmol/l) are defined as having impaired glucose tolerance (IGT). Both IFG and IGT are risk factors for future diabetes.
Normoglycemia is defined as plasma glucose levels <110 mg/dl (6.1 mmol/l) in the FPG and a 2-h postload value <140 mg/dl (7.8 mmol/l) in the OGTT.
If necessary, plasma glucose testing may be performed on individuals who have taken food or drink shortly before testing. Such tests are referred to as random plasma glucose measurements and are given without regard to time of last meal. A random plasma glucose level >160 mg/dl (8.9 mmol/l) is considered a positive screening test result. The diagnosis of diabetes is made on additional testingpreferably by the FPG test, or less preferably, by the OGTTperformed on subsequent days.
Laboratory measurement of plasma glucose concentration is performed on venous samples with enzymatic assay techniques, and the above-mentioned values are based on the use of such methods.
Glycated hemoglobin remains a valuable tool for monitoring glycemia, but it is not currently recommended for the screening or diagnosis of diabetes.
GENERAL RECOMMENDATIONS FOR COMMUNITY SCREENING
Individuals who have been determined to be at risk should be referred to a physician for evaluation. In addition, individuals indicating that they have any diabetes symptoms should seek appropriate medical care. Community screening programs must have an established mechanism for referring individuals to a clinician for further evaluation.
Although there is ample scientific evidence showing that certain risk factors predispose individuals to development of diabetes (Table 1), there is insufficient evidence to conclude that community screening is a cost-effective approach to reduce the morbidity and mortality associated with diabetes in presumably healthy individuals. On the other hand, community screening programs clearly provide a means to enhance public awareness of the seriousness of diabetes and its complications. Thus, based on expert opinion, community screening for diabetes in high-risk populations may be worthwhile, but its true efficacy is unknown. In conclusion, to increase the cost-effectiveness of testing undiagnosed, otherwise healthy individuals, screening should be considered in high-risk populations. This recommendation is consistent with the "Report of the Expert Committee on the Diagnosis and Classification of Diabetes."
Use of GlycemicTesting in Community Screening
Criteria for Glycemic Testing in Community Screening
Some screening programs use blood glucose monitoring devices (meters) approved by the Food and Drug Administration for home use. While testing of capillary blood glucose (e.g., finger-stick glucose) is not the recommended procedure, administrators of programs that use meters should practice regular quality-assurance procedures and be aware of manufacturers' recommendations regarding use of their specific testing devices. Many of these meters measure whole blood glucose and not plasma glucose. Note that plasma glucose values are 1015% higher than whole blood glucose values.
Testing of capillary blood glucose should be done with the patient in the fasting state. Individuals with a fasting capillary whole blood glucose test result >110 mg/dl (6.1 mmol/l) should be referred to a physician for further testing. If necessary, a random test may be performed on individuals who have taken food or drink shortly before testing. An individual with a random capillary whole blood glucose test result >140 mg/dl (7.8 mmol/l) should be referred to a physician for further testing. Testing of blood with a blood glucose monitoring device intended for home use is not considered a diagnostic procedure, even if confirmed on another occasion. Thus, a screening test using whole blood glucose does not constitute the first test in the mandatory two-test procedure for diagnosing diabetes. Thus, a whole blood screening test must be confirmed two more times using plasma from a venous sample.
Table 3 defines glycemic test results that indicate additional testing and evaluation by a physician.
Other Considerations for Community Screening Programs
1. Community screening programs must follow Occupational Safety and Health Administration guidelines.
2. Personnel conducting screening programs must be adequately trained and demonstrate competency in the testing procedure used and in related program policies and procedures. The following topics should be included in a training program:
3. Follow-up should be conducted to verify that individuals who have positive screening test results have sought medical attention. All individuals who have glycemic testing performed must be provided a written record (a paper or computerized copy retained by the organization or facility conducting the screening) containing the following information:
4. Information on alternative health care resources should be made available to individuals who do not have access to a physician.
American Diabetes Association: Gestational diabetes mellitus (Position Statement). Diabetes Care 23 (Suppl. 1):S77S79, 2000.
Engelgau MM, Thompson TJ, Smith PJ, Herman WH, Aubert RE, Gunter EW, Wetterhall SF, Sous ES, Ali MA: Screening for diabetes mellitus in adults: the utility of random capillary blood glucose measurements. Diabetes Care 18:463466, 1995.
Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus. Diabetes Care 23 (Suppl. 1):S4S19, 2000.
Herman WH, Smith PJ, Thompson TJ, Engelgau MM, Aubert RE: A new and simple questionnaire to identify people at increased risk for undiagnosed diabetes. Diabetes Care 18:382387, 1995.
Goldstein DE, Little RR, Lorenz RA, Malone JI, Nathan D, Peterson CM: Tests of glycemia in diabetes (Technical Review). Diabetes Care 18:896909, 1995.
National Institutes of Health, National Institute of Diabetes and Digestive and Kidney Diseases: Diabetes in America. 2nd ed. Washington, DC, U.S. Govt. Printing Office, 1995 (NIH publ. no. 95-1468).
Copyright © 2000American Diabetes
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