Implications of the Revised Criteria for Diagnosis and Classification of Diabetes Mellitus (Editorial‪)‬

Diabetes mellitus is a heterogeneous disease. It comprises several distinct pathophysiologic disorders of carbohydrate metabolism, each of which ultimately manifests with hyperglycemia. Although the prevalence of the disease is unknown, 13 million people are estimated to have diabetes in the US [1]. The severe complications (renal, retinal, and cardiovascular) associated with the disease contribute to the $92 000 000 000 in annual healthcare costs in the US (1992 estimate) [2]. Therefore, the recent Report of the Expert Committee on the Diagnosis and Classification of Diabetes Mellitus that recommends new classification and diagnostic criteria for diabetes [3] merits contemplation. Since the advent of blood glucose assays, the exclusive criterion for the diagnosis of diabetes has been hyperglycemia, either fasting or postprandial. For many years diabetes was diagnosed by the oral glucose tolerance test (OGTT), the cutoff having been established as 2SD above the mean of the glucose concentrations in healthy volunteers. In 1975 Siperstein estimated that more than half the population older than 60 years was abnormal by these criteria [4]. However, those values had more statistical than clinical significance, as follow-up for 10 years revealed that a substantial proportion of these individuals did not develop diabetes and many returned to normal glucose tolerance. Moreover, there was considerable variability among diabetologists in the diagnostic criteria used in practice [5]. To resolve these issues, in 1979 the National Diabetes Data Group [6] proposed criteria that were based on the bimodal distribution of blood glucose concentrations in populations with a high prevalence of diabetes, such as Pima Indians and Nauruans. Optimal separation between nondiabetic and diabetic subjects in these groups is at 11.1 mmol/L (200 mg/dL, 2000 mg/L) 2 h after an oral glucose load and at 7.8 mmol/L (140 mg/dL) for fasting plasma glucose (FPG). Thus, the diagnostic criteria were (a) classic symptoms of diabetes with unequivocal increase of plasma glucose, (b) FPG [greater than or equal to]11.1 mmol/L, or (c) a 2-h (and one other) postload value [greater than or equal to]11.1 mmol/L during an OGTT [6].