Contributions of Fasting and Postprandial Glucose Concentrations to Haemoglobin A1c in Drug-Naive Mal-Glucose Metabolism in Chinese Population Using Continuous Glucose Monitoring System

Aim. To clarify the contributions of fasting glucose (FG) and postprandial glucose (PG) to HbA1c in drug-naive patients with type 2 diabetes (T2D) and impaired glucose tolerate (IGT)/impaired fasting glucose (IFG). Methods. Continuous glucose monitoring (CGM) was performed in 305 drug-naive Chinese patients with T2D or IGT/IFG. The incremental area under the curve (AUC) above a glucose value of 6.1 mmol/L or FG glucose levels were calculated to evaluate the contributions of PG or FG to HbA1c values. Results. According to quintiles of HbA1c, T2D patients were divided into five groups (group 1 to 5), and patients with IGT/IFG were assigned into group 0. PG was the predominant contributor in the lower groups with HbA1c 4.9 similar to 6.0% and 6.1 similar to 7.8%. The relative contributions of FG and PG to HbA1c had no significance in the middle groups of HbA1c (7.9 similar to 8.7% and 8.8 similar to 9.5%). FG contributed significantly more than PG in the higher groups of HbA1c (9.6 similar to 10.9% and 11.0 similar to 14.6%). Regression analyses indicate that the contributions of FG and PG were equal (both 50%) when the level of HbA1c was 8.5%. Conclusions. In drug-naive patients with T2D or IGT/IFG, PG contributed more in patients with HbA1c < 8.5%, whereas FG became the predominant contributor in the poorly controlled patients with HbA1c >= 8.5%. These results may help the health-care provider set appropriate plasma glucose testing goals with the expectation of achieving specific HbA1c values.