Glucose area under the curve during oral glucose tolerance test as an index of glucose intolerance

HbA1c and fasting plasma glucose (FPG) levels are commonly recognized as diagnostic indices for diabetes and glucose intolerance. However, they are not sufficient for clear detection of glucose intolerance in the early stage unless an oral glucose tolerance test (OGTT) is performed. Moreover, even in case of an OGTT, 2-h postprandial plasma glucose (PG) levels, a criterion for glucose intolerance in OGTTs, may not provide complete information regarding glucose tolerance. Whole glucose excursion after OGTT is considered to represent glucose tolerance well, and the glucose area under the curve (AUC) can be an index of glucose excursion. However, few studies have investigated measurement of the glucose AUC in glucose intolerance screening. In the present study, data from 520 OGTTs were analyzed to define the cutoff value for the glucose AUC for glucose intolerance screening. Our results showed that a cutoff value of 290 mg h/dl for the glucose AUC was highly sensitive and specific (90 and 93 %, respectively) for detecting diabetes, impaired glucose tolerance (IGT), and group at increased risk of diabetes (normal glucose tolerance with 1-h PG levels of ≥180 mg/dl after glucose load) and showed a better concordance rate than the use of HbA1c, FPG, or 2-h PG levels. Moreover, the cutoff value for the glucose AUC calculated using the diagnostic criteria in the OGTT (305 mg h/dl) was consistent with the value determined from OGTT analysis. These data suggest a possibility that glucose intolerance screening using a glucose AUC cutoff value of 290 mg h/dl could be useful.