Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus

The Expert Committee on the Diagnosis and Classification of Diabetes Mellitus*

Diabetes Care. 2000;23(1s) 

In This Article

Diagnostic Criteria For Diabetes Mellitus

Type 1 diabetes is usually an autoimmune disease, characterized by the presence of a variety of autoantibodies to protein epitopes on the surface of or within the beta-cells of the pancreas. The presence of such markers before the development of overt disease can identify patients at risk [138]. For example, those with more than one autoantibody (i.e., ICA, IAA, GAD, IA-2) are at high risk [139,140,141]. At this time, however, many reasons preclude the recommendation to test individuals routinely for the presence of any of the immune markers outside of a clinical trials setting. First, cutoff values for some of the assays for immune markers have not been completely established for clinical settings. Second, there is no consensus yet as to what action should be taken when a positive autoantibody test is obtained. Thus, autoantibody testing may identify people at risk of developing type 1 diabetes without offering any proven measures that might prevent or delay the clinical onset of disease. Of note, however, is that there are a number of ongoing well-controlled clinical studies testing various means of preventing type 1 diabetes. These studies conducted in high-risk subjects may one day offer an effective means to prevent type 1 diabetes, in which case screening may become appropriate. Last, because the incidence of type 1 diabetes is low, routine testing of healthy children will identify only the small number (<0.5%) who at that moment may be "prediabetic." Thus, the cost-effectiveness of such screening is questionable, at least until an effective therapy is available. For the above reasons, the clinical testing of individuals for autoantibodies related to type 1 diabetes, outside of research studies, cannot be recommended at this time. Similarly, antibody testing of high-risk individuals (e.g., siblings of type 1 patients) is also not recommended until the efficacy and safety of therapies to prevent or delay type 1 diabetes have been demonstrated. On the other hand, the autoantibody tests may be of value to identify which newly diagnosed patients have immune-mediated type 1 diabetes in circumstances where it is not obvious, particularly when therapies become available to preserve beta-cell mass.

Undiagnosed type 2 diabetes is common in the U.S. As many as 50% of the people with the disease, or about 8 million individuals, are undiagnosed [127]. Of concern, there is epidemiological evidence that retinopathy begins to develop at least 7 years before the clinical diagnosis of type 2 diabetes is made [142]. Because hyperglycemia in type 2 diabetes causes microvascular disease and may cause or contribute to macrovascular disease, undiagnosed diabetes is a serious condition. Patients with undiagnosed type 2 diabetes are at significantly increased risk for coronary heart disease, stroke, and peripheral vascular disease. In addition, they have a greater likelihood of having dyslipidemia, hypertension, and obesity [143].

Thus, early detection, and consequently early treatment, might well reduce the burden of type 2 diabetes and its complications. However, to increase the cost-effectiveness of testing undiagnosed, otherwise healthy individuals, testing should be considered in high-risk populations. Suggested criteria for testing are given in Table 6 . Factors leading to these recommendations include: 1) the steep rise in the incidence of the disease after age 45 years, 2) the negligible likelihood of developing any of the complications of diabetes within a 3-year interval of a negative screening test, and 3) knowledge of the well-documented risk factors for the disease. Although the OGTT and FPG are both suitable tests, in clinical settings, the FPG is strongly recommended because it is easier and faster to perform, more convenient and acceptable to patients, more reproducible, and less expensive.

ACOG, American College of Obstetricians and Gynecologists; FPG, fasting plasma glucose; GCT, glucose challenge test; GDM, gestational diabetes mellitus; HNF, hepatocyte nuclear factor; IFG, impaired fasting glucose; IGT, impaired glucose tolerance; MODY, maturity-onset diabetes of the young; NDDG, National Diabetes Data Group; NHANES III, Third National Health and Nutrition Examination Survey; OGTT, oral glucose tolerance test; PAI-1, plasminogen activator inhibitor-1; WHO, World Health Organization; 2-h PG, 2-h postload glucose.

From the American Diabetes Association, Alexandria, Virginia. Originally approved 1997. Modified in 1999 based on the Proceedings of the Fourth International Workshop-Conference on Gestational Diabetes Mellitus (Diabetes Care 21 [Suppl. 2]:B1-B167, 1998).

*Members of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus: James R. Gavin III, MD, PhD (Chair), K.G.M.M. Alberti, MD, Mayer B. Davidson, MD, Ralph A. DeFronzo, MD, Allan Drash, MD, Steven G. Gabbe, MD, Saul Genuth, MD, Maureen I. Harris, PhD, MPH, Richard Kahn, PhD, Harry Keen, MD, FRCP, William C. Knowler, MD, DrPH, Harold Lebovitz, MD, Noel K. Maclaren, MD, Jerry P. Palmer, MD, Philip Raskin, MD, Robert A. Rizza, MD, and Michael P. Stern, MD.