Distribution of Blood Glucose and the Correlation between Blood Glucose and Hemoglobin A1c Levels in Diabetic Outpatients

PURPOSE OF THE STUDY: Tight glycemic control is important for the prevention of microvascular complications in diabetic patients. We examined the reliability of using blood glucose levels measured at various time-points relative to a meal as an index of glycemic control in Japanese diabetic outpatients. Basic procedures followed: We examined the correlation between the fasting blood glucose (FBG) level; the one-hour (1-h), two-hour (2-h), and three-hour (3-h) post breakfast blood glucose (PBBG) levels, the 1 h, 2 h, and 3 h post lunch blood glucose (PLBG) levels and the hemoglobin A1c (HbA1c) levels in Japanese diabetic outpatients. A total of 11451 patient-visits to the Marunouchi Hospital between January 2002 and December 2002 were included in the study. The main findings: The blood glucose levels measured at all of the above time-points were significantly correlated with the HbA1c level. As calculated using local polynomial regression fitting, the FPG, 1-h, 2-h, and 3-h PBBG levels that corresponded to an HbA1c level of 6.5% were 132 mg/dL, 174 mg/dL, 170 mg/dL, and 143 mg/dL, respectively. The FPG and 2-h PBBG levels exhibited a good sensitivity and specificity for predicting a glycemic control corresponding to an HbA1c<5.8%, while the FPG and 3-h PBBG levels exhibited fair sensitivity and specificity for predicting glycemic control corresponding to an HbA1c<6.5%. The principal conclusions: The FBG, 2-hPBBG, and 3-hPBBG levels can be used as rough estimates of glycemic control in Japanese diabetic outpatients.