Objective: HbA1c values reflect overall glycemic exposure over the past 2-3 months and are determined by both fasting (FPG) and postprandial plasma glucose (PPG) levels. Cross-sectional studies suggest that attainment of HbA1c goals requires specific targeting of postprandial hyperglycemia.
Research design and methods: We undertook a prospective intervention trial to assess the relative contribution of controlling FPG and PPG for achieving recommended HbA1c goals. One hundred and sixty-four patients (90 male and 74 female) with unsatisfactory glycemic control (HbA1c >/=7.5%) were enrolled in an individualized forced titration intensified treatment program.
Results: After 3 months HbA1c levels decreased from 8.7+/-0.1 to 6.5+/-0.1% (p<0.001); FPG decreased from 174+/-4 to 117+/-2mg/dl (p<0.001); PPG decreased from 224+/-4 to 159+/-3mg/dl (p<0.001) and daylong hyperglycemia (average of premeal, postprandial and bedtime plasma glucose excluding FPG) decreased from 199+/-4 to 141+/-2mg/dl (p<0.0001). Patients' weight remained unchanged (84.0+/-1.4kg versus 82.9+/-1.5kg, p=0.36). No severe hypoglycemia occurred. Only 64% of patients achieving FPG targets of <100mg/dl achieved an HbA1c target of <7% whereas 94% of patients achieving the postprandial target of <140mg/dl did. Decreases in PPG accounted for nearly twice as much for the decreases in HbA1c as did decreases in FPG. PPG accounted approximately 80% of HbA1c when HbA1c was <6.2% and only about 40% when HbA1c was above 9.0%.
Conclusions: Control of fasting hyperglycemia is necessary but usually insufficient for achieving HbA1c goals <7%. Control of postprandial hyperglycemia is essential for achieving recommended HbA1c goals.