[Diagnostic criteria for diabetes mellitus]

In the last three years, new diagnostic criteria for diabetes mellitus have been proposed by the American Diabetes Association (ADA, 1997), the World Health Organization (WHO) consultation (1998), and the Japan Diabetes Society (JDS, 1999). The most important change from the previous WHO criteria (1985) to these criteria is a decrease in fasting plasma glucose level (FPG) from 140 mg/dl to 126 mg/dl, which defines diabetes mellitus. These criteria attach more importance to FPG than to plasma glucose levels 2 hours after 75 g glucose load (2 hPG). According to these criteria, for example, in one instance with FPG > or = 126 mg/dl, the diagnosis of diabetes mellitus is warranted, if the postprandial plasma glucose > or = 200 mg/dl or another FPG > or = 126 mg/dl were reconfirmed on a subsequent day. The ADA criteria did not recommend an oral glucose tolerance test (OGTT) for routine clinical use. These criteria has established a new category of impaired fasting glucose (IFG) (> or = 110 mg/dl and 126 < mg/dl), similar to impaired glucose tolerance (IGT) which is recognized by performing OGTT. We have reported from a cohort study that there was only one risk factor for IGF: worsening of metabolic derangement progressing to overt diabetes. With IGT, however, there are two risks: a risk for progression to diabetes, and a risk for development of cardiovascular disease. Therefore it seems that whether or not OGTT should be performed depends on the purpose: simply diagnosing for overt diabetes, or detecting risk factors for cardiovascular disease. The JDS criteria proposed the use of HbA1C as a supporting diagnostic tool, because JDS has achieved a fruitful standardization in Japan to a considerable extent. According to the JDS criteria, a diagnosis of diabetes mellitus can be made by an FPG > or = 126 mg/dl when HbA1C > or = 6.5% is confirmed. It is expected that these new criteria will promote further efforts against the increasing number of patients with diabetes mellitus.