Does the new American Diabetes Association definition for impaired fasting glucose improve its ability to predict type 2 diabetes mellitus in Spanish persons? The Asturias Study.

In 2003, the American Diabetes Association reduced the lower limit defining impaired fasting glucose (IFG) to 100 mg/dL. The aim of this study was to analyze the impact of this change in the definition of IFG in a low-risk white population from northern Spain. The Asturias Study is a prospective, population-based survey of diabetes and cardiovascular risk factors. The baseline examination was carried out between 1998 and 1999 when 1034 individuals (age range, 30-75 years) were randomly selected to determine the prevalence of type 2 diabetes mellitus and prediabetes in the Principality of Asturias (northern Spain). In 2004 to 2005, these same subjects were invited for a follow-up examination. All participants without known diabetes underwent an oral glucose tolerance test both at baseline and follow-up. Application of the new American Diabetes Association definition resulted in 3 times more persons having IFG. The incidence rates of diabetes were 3.8, 19.5, and 58.0 per 1000 person-years in subjects with initial FPG values <100, 100 to 109, and 110 to 125 mg/dL, respectively. Inclusion of persons with an intermediate risk in the 100- to 109-mg/dL zone to the definition of IFG changed its positive predictive value, specificity, and sensitivity to predict diabetes from 36.5%, 94.5%, and 43.2% to 19.9%, 77.3%, and 75%, respectively. Receiver operating characteristics curve analysis including all the baseline fasting plasma glucose levels from 64 to 125 mg/dL depending on their ability to predict diabetes showed that the point closest to the ideal of 100% sensitivity and 100% specificity was 100 mg/dL. In conclusion, this study indicated that lowering the cutoff point for IFG optimizes its ability to predict diabetes in this Spanish population. The addition of other risk factors such as impaired glucose tolerance, hypertriglyceridemia, and overweight to IFG can stratify diabetes risk better.