Six months after transitioning from MDI to pump therapy, patients with poorly controlled type 1 diabetes achieved significantly improved A1C values whether they used a sensor-augmented insulin pump or a conventional pump (the PRT and CSII groups, respectively). The magnitude of improvement within each group was comparable to published data on the efficacy of pump therapy (16
), confirming the superiority of pump therapy over MDI in patients with poorly controlled diabetes.
Among patients who complied with the study protocol, there was a significant between-group difference favoring the sensor-augmented over the conventional insulin pump. However, when protocol-noncompliant patients were included, the A1C improvement was not significant between the PRT and CSII groups.
During the 9-day period between screening and study baseline, the PRT group was trained on sensor use and allowed to modify their MDI dosing regimens based on CGM readings. The decrease observed in A1C levels during this short interval may represent the immediate benefit of exposure to CGM data, even in the absence of an insulin pump. The initial decline in A1C levels seen in the PRT group may also explain the blunting of the difference observed between baseline and study end. A more meaningful comparison may, therefore, be between screening and study end.
MAGE and SD calculations revealed a significantly greater reduction in the PRT group compared with that in the CSII group for the entire study population. The improvements in MAGE and SD values were reached without any increase in the number or duration of hypoglycemic events.
Improvements in glycemic control in the PRT group beyond those seen in the CSII group may be attributable to alarms and glucose trend information available to patients during the study, prompting patients in the PRT group to engage in more lifestyle modifications and insulin treatment adjustments.
Recent studies reported that CGM was beneficial in lowering A1C. In the GuardControl study (12
), A1C was reduced by ≥2% in 26% of patients after 3 months of continuous sensor use but not by intermittent use. Hirsch et al. (14
) reported that the effectiveness of sensor-augmented pump therapy was contingent on patients' compliance with glucose sensor use. Wearing a CGM sensor >60% of the time was associated with lowered A1C levels. The JDRF study (13
) recently showed that CGM improved A1C in adults with well-controlled type 1 diabetes wearing the continuous glucose sensor for 83% of the requested time. Although sensor compliance was less consistent in other age-groups, compliant patients still benefited from the technology (13
Failure to adhere to many aspects of diabetes management is recognized as an obstacle for successful treatment in adolescents and young adults (17
). In the present study, subjects in the 15- to 24-year-old age-group had the highest probability of being noncompliant with the sensor protocol. Our findings support the fact that CGM should be used at least 70% of the time to improve metabolic control when pump therapy is initiated and show that even patients whose diabetes had been poorly controlled previously with intensified MDI regimens may realize A1C reductions. Patients' motivation to use CGM as an adjunct to insulin pump therapy is crucial for device effectiveness. Trained health care provider teams should focus on how to adequately select, train, manage, and motivate patients to optimize benefits from CGM.
The high attrition rate of this study can be considered as a limitation of this trial and is best explained by the lack of a run-in period, which could have been used to select the most well-motivated patients. In addition, the short duration of this trial does not provide information on the long-term impact of the treatment.
In summary, patients who use CGM-enabled pumps and who wear sensors at least 70% of the time realize glycemic benefits beyond those who do not wear sensors or who use conventional insulin pumps. Exposure to CGM data, even before transitioning from MDI to an insulin pump, can lead to A1C reductions. Reduction of hyperglycemia without an increased risk of hypoglycemia can be achieved by a combination of modified insulin administration and lifestyle changes.