One-Hour Plasma Glucose Predicts the Progression From Normal Glucose Tolerance to Prediabetes

Abstract

OBJECTIVE To examine the ability of the 1-h plasma glucose (PG) concentration during the oral glucose tolerance test (OGTT) to predict the risk of progression to prediabetes in individuals with normal glucose tolerance (NGT). RESEARCH DESIGN AND METHODS A total of 1,557 participants from the San Antonio Heart Study who were free of type 2 diabetes at baseline, had a baseline OGTT, and had a repeat OGTT after 7.5 years of follow-up were evaluated. The ability of 1-h PG concentration to predict the development of prediabetes, based on American Diabetes Association criteria, was evaluated. RESULTS Approximately one-quarter of participants with NGT (24.7%) progressed to prediabetes at 7.5 years (22.5% with 1-h PG <155 mg/dL and 42.5% with 1-h PG >155 mg/dL). The 1-h PG was the strongest predictor of developing prediabetes, and a 1-h cut point of 120 mg/dL had 61% sensitivity and 67% specificity in identifying individuals with NGT at high risk of developing prediabetes. Participants with a 1-h PG of 120–155 mg/dL and who experienced a deterioration in glucose tolerance (progression to prediabetes) at follow-up were characterized by severe insulin resistance and metabolic abnormalities characteristic of the insulin resistance syndrome. Therefore, we suggest the term pre-prediabetes for this group to emphasize their high future risk of deteriorating glucose tolerance. CONCLUSIONS An increase in 1-h PG concentration precedes the development of prediabetes and identifies individuals with a 1-h PG of 120–155 mg/dL who are at increased risk of developing prediabetes. Therefore, we suggest the term pre-prediabetes for this group with an elevated risk of deteriorating glucose tolerance.