New classification and diagnostic criteria for diabetes mellitus

There has been an explosive growth in knowledge about diabetes mellitus since the National Diabetes Data Group promulgated diagnostic criteria and a classification system in 1979 that was largely adopted by the World Health Organization. However, recent findings regarding the levels of glucose associated with development of retinopathy, and growing confusion caused by a system of classification of diabetes based largely on the treatment used have led to a new assessment of the diagnosis and classification of diabetes mellitus. Using new data from population-based studies, and placing emphasis on a pathophysiology-based system of classification, in 1997, the Expert Committee of the American Diabetes Association released its recommendations for the classification and diagnosis of diabetes. The major changes from the 1979 report include: (a) the preferred use of the terms "type 1" and "type 2" instead of "insulin-dependent" and "non-insulin-dependent" to designate the two major types of diabetes mellitus; (b) a simplification of the diagnostic test to two fasting plasma glucose (FPG) determinations; and (c) a lower cutoff for FPG (126 mg/dL) to diagnose diabetes (this level of FPG having been found equivalent to the 200-mg/dL value in the oral glucose tolerance test for diagnosis). These changes provide an easier and more reliable means of diagnosing persons at risk of complications of hyperglycemia. Even though the fasting criterion was lowered, the total number of persons who will be diagnosed with diabetes by exclusive reliance on FPG will actually be somewhat less than with the old criteria. Moreover, epidemiologic data support the recommendation that screening for diabetes should start at age 45 and be repeated every 3 years in persons without risk factors, and earlier and more often in those with risk factors.