Relationship between HbA1c and indices of glucose tolerance derived from a standardized meal test in newly diagnosed treatment naive subjects with Type 2 diabetes

AIMS: To determine the relationship between HbA1c and other indices of glycaemic status derived during a standardized meal tolerance test (MTT) in newly diagnosed treatment-naive subjects with Type 2 diabetes (T2DM). METHODS: T2DM subjects (n = 262) consumed a standard MTT in the morning after a 10-h overnight fast. Frequent samples for plasma glucose (PG) were collected over the 4-h test period. The relationship between HbA1c and other glycaemic indices derived from the MTT were explored. The postprandial glucose exposure was calculated as the area under the incremental plasma glucose curve above the fasting level for the test period (AUC1). Excess hyperglycaemia was calculated as the AUC0-4 h above the arbitrary PG concentrations of 6.0 mmol/l (AUC2) and 5.5 mmol/l (AUC3), respectively [upper limit of fasting normoglycaemia according to World Health Organization (WHO) and American Diabetes Association (ADA), respectively]. Fasting hyperglycaemia was also estimated, being the difference between each of the above and the postprandial excursion. The participants were divided into three subgroups according to HbA1c (Group 1, 9.0%) and the relative contribution calculated of the postprandial glucose and fasting hyperglycaemia to the excess hyperglycaemia above the designated international thresholds for fasting plasma glucose. RESULTS: HbA1c was more strongly correlated with the fasting plasma glucose (r = 0.85, P