Analysis of Insulin Receiver Operating Characteristic Curve for Impaired Glucose Tolerance and Impaired Fasting Glucose Diagnosis

Impaired glucose tolerance (IGT), impaired fasting glucose (IFG) and insulin resistance (IR) are prediabetic conditions diagnosed by glucose and insulin values measured by oral glucose tolerance test (OGTT). In the OGTT, insulin and glucose levels are measured in five different blood samples: a sample in fasting (minute 0) and four others after oral intake of 75 gr. of glucose, at intervals of 30 minutes (minute 30, 60, 90 and 120). The values of glucose at 0 and 120 minutes from OGTT are used for the diagnosis of IFG and IGT, respectively. Several parameters had been used to diagnose the IGT and IFG, such as abdominal circumference, HOMA-IR, area under the curve of glucose during OGTT, among others. However, none of these studies have explored obtaining cut-off points from the area under the curve of insulin (AUC
_I
) during OGTT for IGT and IFG diagnosis. For this propose a database of 172 subjects with values of glucose and insulin during OGTT was used. To assess the predictive capacity of AUC
_I
the receiver operating characteristic (ROC) curves were performed and it was calculated the area under the ROC curve (AUC
_ROC
), negative predictive value (NPV) and positive predictive value (PPV). The results show that AUC
_I
can predict the IFG (AUC
_ROC
=0.71) and IGT (AUC
_ROC
=0.65). The AUC
_I
can discriminate between the subjects that undergo IFG and IGT in concomitance from the subjects that only undergo one of the pathologies. All these findings suggested that AUC
_I
could be used as a diagnostic method for IFG and IGT.