Difference between observed and predicted glycated hemoglobin at baseline and treatment response to vildagliptin-based dual oral therapy in patients with type 2 diabetes.

AIM:We aimed to investigate the association of difference between observed and predicted glycated hemoglobin (dopHbA1c) and HbA1c reduction after vildagliptin-based oral therapy in patients with type 2 diabetes (T2D). METHODS:This was a prospective observational study. Adults ≥ 20 years old with T2D and HbA1c ≧7% treated with oral anti-diabetic drugs (OADs) were eligible if their OADs were shifted to vildagliptin-based dual oral therapy. Fasting plasma glucose (FPG) and HbA1c were recorded at baseline, week 12, and week 24. To determine baseline dopHbA1c, a predicted HbA1c was calculated by inserting baseline FPG into a regression equation (HbA1c = FPG ∗ 0.0225 + 4.3806) developed from linear relationship between HbA1c and FPG in an independent cohort of 3239 outpatients with T2D (dopHbA1c = observed HbA1c - predicted HbA1c). Patients were assigned to low (≦0) or high (>0) dopHbA1c group according to their baseline dopHbA1c levels. The study endpoint was changes from baseline to week 24 in HbA1c levels. RESULTS:A total of 1224 patients were enrolled. Patients with a dopHbA1c >0 had a greater HbA1c reduction after vildagliptin-based dual oral therapy than those with a dopHbA1c ≦0 (-1.5 ± 2.0 vs. -0.4 ± 1.0%, p < 0.001). Baseline dopHbA1c was positively associated with HbA1c reduction from baseline to week 24 (β coefficient 0.883, 95% CI 0.811 to 0.955, p < 0.001), and the association remained significant after adjustment for confounders. CONCLUSIONS:In T2D patients with an HbA1c ≧7%, a higher baseline dopHbA1c was associated with a greater HbA1c reduction after shifting to vildagliptin-based dual oral therapy.