Impact of differences in glucose tolerance on the prevalence of a negative insulinogenic index

Objective: To determine the prevalence of a negative insulinogenic index (change in plasma insulin/change in plasma glucose from 0 to 30 min) from an oral glucose tolerance test according to glucose tolerance category. Materials and Methods: Data from the San Antonio Heart Study (n = 2494), Japanese American Community Diabetes Study (JACDS; n = 594) and Genetics of NIDDM Study (n = 1519) were examined. Glucose tolerance was defined by ADA criteria. Results: In the combined cohort, the prevalence of a negative insulinogenic index was significantly higher in diabetes 20/616 (3.2%) compared to normal glucose tolerance 43/2667 (1.6%) (p < 0.05). Longitudinally, in the JACDS cohort, the prevalence did not change from baseline (3/594; 0.5%) to 5 (4/505; 0.7%) and 10 years (8/426; 1.9%) (p = 0.9) and no subject had a repeat negative insulinogenic index. Conclusions: A negative insulinogenic index occurs at a low prevalence across glucose tolerance categories although more often in diabetes, but without recurrence over time.