July 31, 2008 — The plasma glucose concentration at 1 hour during the oral glucose tolerance test (OGTT) is a strong predictor of the risk for type 2 diabetes, according to the results of a study reported in the August issue of Diabetes Care.

"In longitudinal epidemiological studies, ~40% of subjects who develop type 2 diabetes have normal glucose tolerance (NGT) at baseline, indicating that there is a population of NGT subjects who are at risk for future type 2 diabetes," write Muhammad A. Abdul-Ghani, MD, PhD, from the University of Texas Health Science Center at San Antonio, and colleagues. "Recently, we demonstrated that subjects with NGT, despite having relatively low risk for type 2 diabetes, can be stratified into low- and high-risk categories based upon the relationship between their postload and fasting plasma glucose (FPG) concentrations."

The goal of this study was to evaluate the efficacy of 1-hour plasma glucose concentration and the metabolic syndrome to predict the risk for type 2 diabetes, using data from a study cohort of 1611 participants who were enrolled in the San Antonio Heart Study and who were free of type 2 diabetes at baseline. Plasma glucose and insulin concentrations were measured at 0, 30, 60, and 120 minutes during the OGTT. The investigators tested 2 models using glucose tolerance status, 1-hour plasma glucose concentration, and the presence of the metabolic syndrome for their ability to predict the risk for type 2 diabetes at 7 to 8 years of follow-up, based on results of an OGTT.
 

Using a cutoff point of 155 mg/dL for the 1-hour plasma glucose concentration during the OGTT, participants in each glucose tolerance group were stratified into low, intermediate, and high risk for type 2 diabetes. A model using 1-hour plasma glucose concentration, Adult Treatment Panel III criteria for the metabolic syndrome, and fasting plasma glucose level independent of 2-hour plasma glucose level was equally effective in stratifying participants without diabetes into low, intermediate, and high risk for type 2 diabetes. This model also identified a group of normal glucose-tolerant participants who were at very high risk for type 2 diabetes.

"The plasma glucose concentration at 1 h during the OGTT is a strong predictor of future risk for type 2 diabetes," the study authors write. "A plasma glucose cutoff point of 155 mg/dL and the ATP [Adult Treatment Panel] III criteria for the metabolic syndrome can be used to stratify nondiabetic subjects into three risk groups: low, intermediate, and high risk."

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Diabetes Care. 2008;31:1650-1655.