Background: The automatic Threshold Suspend (TS) feature of the MiniMed 530G system (Medtronic MiniMed, Inc., Northridge, CA), when enabled, suspends insulin delivery for up to 2 h when the sensor glucose (SG) value reaches a preset threshold.
Materials and methods: SG data from 20,973 patients who enabled the TS feature at their discretion and uploaded pump and sensor data to CareLink(®) (Medtronic MiniMed, Inc.) from October 15, 2013 to July 21, 2014 were analyzed. Comparisons between 758,382 patient-days wherein the TS feature was enabled at any time and 166,791 patient-days in which it was not enabled were made. Further comparisons were made between data collected during daytime (8:00 a.m. to 10:00 p.m.) and nighttime (10:00 p.m. to 8:00 a.m.) hours. Data from subsets of patients who enabled the TS feature all of the time (n=14,673) versus those who never enabled the TS feature (n=2,249) were also compared. Recovery from hypoglycemia during and after 2-h pump suspension events was also assessed.
Results: The TS feature was enabled on 82% of patient-days. Patient-days in which the TS feature was enabled, compared with patient-days in which it was not, had 69% fewer SG values ≤50 mg/dL (0.64% vs. 2.09%, respectively; P<0.001). The reduction in hypoglycemia seen on TS-enabled days was more pronounced during nighttime than during daytime hours. SG data from full-time users of the TS feature reflected a 62% reduction in values ≤50 mg/dL and a 5.6% reduction in values ≥300 mg/dL compared with data from nonusers (P<0.001 for each). The median SG value at the start of 2-h suspensions was 60 (interquartile range [IQR], 57-66) mg/dL, immediately after was 87 (IQR, 63-123) mg/dL, and 4 h later was 164 (IQR, 117-220) mg/dL.
Conclusions: The TS feature, when enabled consistently, reduced hypoglycemic exposure, and for those who had it enabled 100% of the time, hyperglycemia was also reduced.