Background: It is generally held that basal insulin substitution with continuous subcutaneous insulin infusion (CSII) provides less variable glucose levels than with long-acting insulin analogs, e.g., glargine, in patients with type 1 diabetes, although this has not been convincingly demonstrated by continuous glucose monitoring.
Methods: To compare glucose control assessed by a continuous glucose monitoring system (CGMS) during basal insulin substitution with glargine versus CSII, we conducted a non-blinded, randomized, crossover trial in 15 type 1 diabetes patients experienced with CSII. All subjects were randomly assigned to receive either a morning dose of insulin glargine, comprising their average 24-h basal insulin requirement, minus 2.4 U, which was delivered by the pump, or to continue as before for 4 weeks followed by a 1-week washout period and a crossover. All mealtime doses of insulin were given by the pump as before. CGMS data were blinded until the end of the study.
Results: The mean blood glucose was lower in the non-glargine arm according to self-monitoring of plasma glucose (9.2 vs. 10.6 mmol/L; P = 0.010) and CGMS (9.1 vs. 10.3 mmol/L; P = 0.002), and hemoglobin A1c was 6.5% without glargine versus 6.8% with (P = 0.018). There were no significant differences in glucose variability measured as SD of plasma glucose (SDPG) or mean amplitude of glycemic excursions (MAGE), although significantly longer periods of glucose values spent within the target of 4.5-10.0 mmol/L were demonstrated in the non-glargine arm using CGMS (P = 0.034). More episodes below 3.5 mmol/L were seen during the CSII period (P = 0.053).
Conclusions: CSII provided improved glucose control compared to glargine with a lower mean plasma glucose and longer periods of glucose values within target on a somewhat lower insulin dose. There was a tendency with more episodes below 3.5 mmol/L during CSII. No difference with respect to glucose variability was found when calculated as SDPG or MAGE.