If ADA criteria accepted 1-hour glucose value in OGTT as a diagnostic criteria for T2DM: What would change? Risk study results-V

The RISK Study was designed to evaluate the efficacy of 1-h and 2-h 75-g OGTT results in the screening of IGT and diabetes according to the American Diabetes Association (ADA) criteria. This study comprises 6620 subjects (mean age: 52.9±11.5 years) from 191 centers, who were at increased risk of T2DM according to the ADA criteria. Subjects were grouped as IFG (100-125 mg/dl), Impaired Glucose Tolerance (IGT) (140-199 mg/dl) and Diabetes Group (DG) (>200 mg/dl) according to fasting glucose and OGTT. 1-h OGTT results were grouped as IGT1 and DG1, and 2-h OGTT results as IGT2 and DG2. The OGTT results revealed IGT1 in 43.7%, DG1 in 21.9%, IGT2 in 26.4%, DG2 in 11.2% of the subjects. IFG prevalence was 41.7% and 54.2% in IGT1 and IGT2 groups respectively. Sensitivity of 1-h/2-h OGTT for DM diagnosis was 62.4% and 51.2%, and specificity was 83.9% and 93.2% respectively. In conclusion, if only 2-h glucose levels were considered, 61% of subjects with IGT and 18.6% of those with DM according to 1-h OGTT would be missed. Furthermore, 42% of DM cases according to 1-h results would be treated as prediabetes. IFG was more correlated with 2-h OGTT levels when compared to 1-h. These results show that evaluation of 1-h glucose levels in addition to 2-h results should be opened to discussion as an important factor that could increase sensitivity and specificity of ADA diagnostic criteria for IGT and diabetes.