Fasting and post-prandial glycemia and their correlation with glycated hemoglobin in type 2 diabetes

Objective: The relative contribution of fasting and post-prandial glucose to glycated hemoglobin (HbA(1c)) is controversial. In the present study, we assessed the relationship with HbA(1c), of fasting and post-prandial glucose measured in a more naturalistic setting, through home glucose self-monitoring or with a continuous glucose monitoring system (CGM). Materials and methods: A consecutive series of 300 patients with Type 2 diabetes were enrolled in the study, provided that they performed blood glucose self-monitoring. HbA(1c), and fasting plasma glucose (FPG) were measured at enrolment. Results: Both fasting plasma and capillary glucose showed a significant correlation with HbA(1c) (r=0.66 and 0.61, respectively; p < 0.001). When home glucose monitoring was considered, both mean fasting and post-prandial glucose showed a significant correlation with HbA(1c), (r=0.71 and 0.73, respectively). In patients in the lower tertile of body mass index (BMI), HbA(1c) showed a significant correlation at multivariate analysis with post-prandial glucose, but not with fasting glucose. In patients with HbA(1c) > 7%, both fasting and post-prandial glucose showed a significant correlation, after adjustment for age and BMI, with HbA(1c) (both p < 0.01); conversely, in those with HbA(1c) <= 7%, such a correlation could be observed for fasting (p < 0.01), but not for postprandial glucose. Conclusion: In conclusion, both fasting and post-prandial glucose contribute to the determination of HbA(1c). Home glucose self-monitoring appears to provide a more accurate assessment of metabolic control than a single plasma glucose measurement in experimental conditions. Fasting glucose could provide a greater contribution to HbA(1c) in patients with lower HbAlc, while post-prandial glucose seems to play a major role in leaner Type 2 diabetic subjects.