Blood Glucose Area Under the Curve: Methodological Aspects

To specify the influence of methods used in estimating area under the curve (AUC) and the meaning of total and incremental AUC, 75 glycemic responses to a mixed meal were studied in 75 diabetic patients, 39 with insulin-dependent diabetes mellitus and 36 with non-insulin-dependent diabetes mellitus. AUC was integrated with five computerized methods: polynomial interpolation of third and fourth degree, trapezoidal rule, Simpson's integration, and cubic interpolatory splines. Although these methods gave significantly different results (P less than 0.001), a strong correlation was found between estimations of AUC with different methods (r greater than 0.99, P less than 0.001). In addition, variation between methods was less than or equal to 2%, whereas the coefficient of variation between subjects was 38%. Total AUC was strongly correlated with basal blood glucose value (r = 0.90, P less than 0.001), whereas incremental and positive AUC were not (r = 0.12 and 0.07, respectively, NS). Incremental and positive AUC were strongly correlated with glycemic rise (r = 0.89 and 0.93, respectively, P less than 0.001), whereas total AUC was only slightly so (r = 0.31, P less than 0.01). Incremental and positive AUC gave slightly but significantly different information on glucose response. These results suggest that variations related to the method used in estimating AUC are not clinically relevant and that a simple method such as trapezoidal rule can be used. Total AUC is a descriptive factor related to basal blood glucose value, whereas incremental and positive AUC more accurately describe glycemic response to foods.