Risk of future diabetes is as high with abnormal intermediate post-glucose response as with impaired glucose tolerance.

AIMS This analysis was done to compare the risk of development of diabetes among subjects with impaired glucose tolerance (IGT) and early glucose intolerance (EGI; intermediary post glucose level > or = 160 mg/dl) when compared with normal (NGT). Profile of insulin secretion and insulin resistance was compared in a subgroup of subjects with EGI, IGT and diabetes. PATIENTS AND METHODS A program on 'primary prevention of diabetes' was initiated and high risk subjects were encouraged to join the program and were followed up. Out of 4084 (M:F 2344:1740) subjects enrolled in the program, a total of 1659 (M:F 1044:615) subjects with mean age 41.3 +/- 10.2 years who had at least two follow up visits were selected for this analysis. OGTTs were performed once in every 6 months. The median follow up duration was 5 years. The conversion rate to diabetes in subjects with persistent IGT or EGI was determined. In a subgroup of subjects, NGT (n = 118), IGT (n = 68), EGI (n = 106) and new DM (n = 126), plasma insulin at fasting, 30 min and 2 hr were measured and insulin resistance (HOMA-IR) was calculated by HOMA method. Insulinogenic index (DeltaI/G) was also calculated. RESULTS The rate of conversion of IGT 251 (40.5%) and EGI 210 (36.5%) subjects to diabetes was similar and significantly higher when compared with the NGT subjects 99 (21.3%). Similar results were noted both in men and women. By using ROC procedure, a cut - off value of one hour post glucose of > or = 160 mg/dl gave a sensitivity of 80% and specificity of 70% to detect abnormal glucose tolerance. In a subset of subjects studied, it was noted that subjects with EGI had significantly higher fasting insulin values than NGT. Insulin resistance (IR) was the highest in DM [Geometric mean (SD)] 6.6 (1.9)), followed by EGI (4.5 (2.3)) (p < 0.0001 vs NGT, 2.9 (2.4)) and IGT (3.9 (2.2)). Insulinogenic index was normal in EGI, NGT and IGT, and it was lower in DM in comparison with other groups. The multiple logistic regression analysis showed that EGI (odds ratio (OR) 2.11) and development of diabetes was strongly associated. The survival curve (time free from diabetes) showed that the median survival time for NGT, EGI and IGT were 18.7, 11.6 and 9.6 yrs respectively. CONCLUSION EGI which is a distinct entity with abnormal intermediate glucose response in glucose tolerance test (GTT) appears to be a risk factor similar to IGT in the development of diabetes. They had higher insulin resistance with normal insulin secretion. Therefore, it is important to determine the intermediate value also during the GTT in addition to fasting and 2 hr post glucose values.