Long-Term Home Study on Nocturnal Hypoglycemic Alarms Using a New Fully Implantable Continuous Glucose Monitoring System in Type 1 Diabetes

Background: This study analyzed the overall nocturnal performance during home use of a long-term subcutaneous implantable continuous glucose monitoring (CGM) sensor. Subjects and Methods: In this study, 12 subjects with type 1 diabetes mellitus (T1DM) (meanSD age, 378 years; mean +/- SD disease duration, 11 +/- 6 years) were implanted with an investigational continuous glucose sensor in the upper arm for up to 90 days. All subjects received full access to real-time glucose display and user programmable hypo- and hyperglycemic alarms. Subjects calibrated the sensors with a self-monitoring of blood glucose (SMBG) meter and continued to rely on their regular SMBG measurements for their diabetes management. Accuracy of the sensors during the home-use study was calculated using SMBG as the reference. The nocturnal sensor attenuation (NSA) concept was tested. Sensitivity and specificity of the nocturnal hypoglycemic alarm were calculated. Results: Mean +/- SD glucose sensor life span was 87 +/- 7 days. The mean +/- SE absolute relative difference over the range of 40-400mg/dL for the sensors in this home-use study was 12.3 +/- 0.7% using SMBG as the reference. The hypoglycemia alarms were set to be triggered when the glucose level went below 70mg/dL. Percentage of nights with hypoglycemic alarms triggered for at least 10min was 13.6%. Recovery into euglycemia within 30min from the timestamp of the immediate confirmatory SMBG testing was obtained in 74% of all episodes (n=20). The implanted continuous glucose sensor showed a hypoglycemia detection sensitivity and specificity of 77% and 96%, respectively. The NSA-associated high negative rate of change of at least -4mg/dL/min was not encountered during night use of the system. Conclusions: This home-use study of a fully implantable, long-term continuous glucose sensor shows excellent performance in nocturnal hypoglycemia detection in T1DM patients. The apparent lack of NSA affecting the implanted sensor and the high specificity of the hypoglycemic alarm expedite the recovery from nighttime hypoglycemia.