The effect of blood glucose concentration on labile A1c in diabetic patients.

We investigated the magnitude of labile A1c in total A1c measured rapidly by a chromatographic method, and whether or not there was an effect of blood glucose before and after a meal on labile A1c in 94 type I and 178 type II diabetic subjects. There were strong correlations between serum glucose and labile A1c both in type I (r = 0.76, P less than 0.001) and in type II diabetic subjects (r = 0.72, P less than 0.001). These relationships did not change before and after the meal. As labile A1c increased in proportion to blood glucose, it could be calculated from the blood glucose level in simultaneous blood samples. In type I diabetic subjects, below the 100-mg/dl glucose level labile a was negligible, and above 100 mg/dl about 0.35% labile A1c was increased every 50-mg/dl increment of glucose. In type II diabetic subjects, below a 150-mg/dl glucose level labile A1c was in the normal range (0.58 +/- 0.15%), and above the 150-mg/dl glucose level every 50-mg/dl increment of glucose increased about 0.3% of labile A1c. If this process is used, stable A1c can be calculated easily from total A1c and coincident serum glucose, even though labile A1c is not removed by incubation.