The necessity of identifying the basal glucose set-point in the IVGTT for patients with Type 2 Diabetes

BACKGROUND: The model-based dynamic insulin sensitivity and secretion test (DISST) uses fasting glucose (G(0)) as the basal glucose (G(B)) concentration when assessing insulin sensitivity (SI). However, this model was developed in a healthy, normoglycaemic cohort. We sought to determine the suitability the DISST model has for individuals with established type 2 diabetes (T2D). METHODS: 14 participants with established T2D were recruited to take part in a dietary intervention study. Insulin-modified intravenous glucose tolerance tests (IM-IVGTT) were undertaken at week 0, 12 and 24 and were used with DISST model to identify G(B). A total of 36 tests were conducted across 12 participants throughout the study. Measured G(0) and identified G(B) values were compared using a Kolmogorov-Smirnov (KS) and signed rank (RS) test for the cohort. RESULTS: There were significant differences between the G(0) and identified G(B) values in this cohort (p(rs) and p(ks) < 0.0001), although both values were well correlated (R = 0.70). The residual plot demonstrates that the modified model captures the behaviour of the participants more accurately than the original model. CONCLUSIONS: This analysis has shown that G(B) is an important variable for modelling the glycaemic behaviour in T2D. These findings suggest that the original DISST model, while appropriate for normoglycaemic cohorts, needs to model basal glucose level as a variable for assessing individuals with established T2D.