Point: Impaired Fasting Glucose: The Case for the New American Diabetes Association Criterion

Abstract

In 1979 and 1980, both the National Diabetes Data Group (1) and the World Health Organization (WHO) (2) formally defined a postchallenge state of glucose tolerance that lay between what was considered normal and diabetic. This state was defined as an elevated 2-h plasma glucose with a nondiabetic fasting glucose level and was termed “impaired glucose tolerance” (IGT). Those individuals falling within the new IGT range were known to have an increased risk of future diabetes and of cardiovascular disease (CVD). It took almost another 20 years to officially recognize that a similar category existed for elevated, but nondiabetic, fasting glucose levels. In 1997 and 1999, the American Diabetes Association (ADA) and the WHO, respectively, added the term “impaired fasting glucose” (IFG) (with the WHO using “impaired fasting glycemia”) to the available diagnostic categories (3,4). It was defined as a fasting plasma glucose (FPG) of 110–125 mg/dl (6.1–6.9 mmol/l). While it was clear that FPG values below the diabetes threshold were predictive of future diabetes and CVD, it was less obvious where the appropriate cut point between normal and IFG status should lie. The report of the ADA’s 1997 Expert Committee on the Diagnosis and Classification of Diabetes (3) cites several earlier studies on which the cut point of 110 mg/dl (6.1 mmol/l) was based. The first is, in fact, the origin of both the name, IFG, and the cut point (5). In an analysis of the Paris Prospective Study, Charles et al. (5) selected a group of people just below the then fasting diabetes threshold of 140 mg/dl (7.8 mmol/l) from the cohort to determine whether elevated, nondiabetic fasting glucose levels were comparable to IGT in predicting incident diabetes. To make the comparison with IGT even handed, they chose a fasting glucose cut point that would include …