A Step Backward—or Is it Forward?

Abstract

The time may have come—or at least will soon arrive—when the diagnostic categories related to diabetes and its close relatives, impaired glucose tolerance (IGT) and impaired fasting glucose (IFG), should be reconsidered. IGT, IFG, and the combination of the two are now considered pre-diabetes because, compared with normal glucose tolerance, they signal an increased risk of developing diabetes (1). Before 1979, when the National Diabetes Data Group defined IGT (2) and declared it to be an official diagnostic category, one either did or did not have diabetes and nondiagnostic glucose levels were de facto “normal.” A middle ground was recognized by some physicians, but it was not enshrined in all epidemiological studies or in clinical practice. The addition of IFG in 1997 for the purpose of creating a state equivalent to IGT both added to the middle ground and raised awareness and appreciation of intermediate levels of glucose intolerance (3). There was now a distinctive group of individuals whose fasting plasma glucose (FPG) lay between normal (<110 mg/dl) and the new 1997 lower diabetes cut point of 126 mg/dl and who may not meet the IGT criterion of 140–199 mg/dl 2 h after a standard oral glucose load of 75 g (3). A further refinement of IFG in 2003 altered the lower IFG cut point from 110 to 100 mg/dl, a change recommended to make both intermediate states equivalent and to define a more realistic upper limit of normal (4). Recently, however, more and more studies have demonstrated that at glycemic levels above normal but within the range of either IFG or IGT, there is an increasing risk of crossing the diabetes line (FPG 126 mg/dl and/or a 2-h post–glucose load level of 200 mg/dl) within a few years (1). These latter numbers are based on the association of …