Fasting Versus Postload Plasma Glucose Concentration and the Risk for Future Type 2 Diabetes

OBJECTIVE The purpose of this study was to assess the efficacy of the postload plasma glucose concentration in predicting future risk of type 2 diabetes, compared with prediction models based on measurement of the fasting plasma glucose (FPG) concentration. RESEARCH DESIGN AND METHODS A total of 2,442 subjects from the Botnia Study, who were free of type 2 diabetes at baseline, received an oral glucose tolerance test (OGTT) at baseline and after 7-8 years of follow-up. Future risk for type 2 diabetes was assessed with area under the receiver-operating characteristic curve for prediction models based up measurement of the FPG concentration 1) with or without a 1-h plasma glucose concentration during the OGTT and 2) with or without the metabolic syndrome. RESULTS Prediction models based on measurement of the FPG concentration were weak predictors for the risk of future type 2 diabetes. Addition of a 1-h plasma glucose concentration markedly enhanced prediction of the risk of future type 2 diabetes. A cut point of 155 mg/dl for the 1-h plasma glucose concentration during the OGTT and presence of the metabolic syndrome were used to stratify subjects in each glucose tolerance group into low, intermediate, and high risk for future type 2 diabetes. CONCLUSIONS The plasma glucose concentration at 1 h during the OGTT is a strong predictor of future risk for type 2 diabetes and adds to the prediction power of models based on measurements made during the fasting state. A plasma glucose cut point of 155 mg/dl plus the Adult Treatment Panel III criteria for the metabolic syndrome can be used to stratify nondiabetic subjects into low-, intermediate-, and high-risk groups.