Intensive insulin therapy requires patients to estimate their carbohydrates and calculate their insulin boluses. Thus, Bolus calculation and carbohydrate estimation are two basic and essential skills that are considered relevant for achieving good glycemic control. However, data is missing as to how the performance in these two skills affects glycemic control. A linear regression analysis was performed with glycemic control as dependent variable. Independent variables of interest were the bolus calculation and carbohydrate estimation skills. We assessed the two skills through the recently evaluated SMART-tool that consists of 10 items for Bolus calculation and 12 items for carbohydrate estimation. Furthermore, demographic (age, gender, years of education) and medical (diabetes type, diabetes duration, body-mass-index, late complications, frequency of SMBG, CSII therapy) variables were controlled for. An additional logistic regression analysis was performed with HbA1c < 7.5% as categorical dependent variable. 311 patients with type 1 or type 2 diabetes treated with an intensive insulin therapy (MDI, CSII) were analyzed. In the linear regression analysis, better Bolus calculation was associated with better glycemic control (beta= -0.22, p<.001) while carbohydrate estimation was not significant (beta=-0.1, p=.088). In the logistic regression analysis, the chance to achieve optimal glycemic control (HbA1c < 7.5%) was significantly increased by 17% (odds ratio=1.17, p=.011) with every correct answer in the Bolus calculation scale. Again, carbohydrate estimation was not significant (OR=0.98, p=.79).
The results demonstrated the importance of good Bolus calculation skills within intensive insulin therapy. Thus, Bolus calculation skills should be regularly assessed in clinical practice. Consequently, patients with deficits in Bolus calculation should receive immediate training or support e.g. via Bolus calculators.