What are the most accurate Continuous Glucose Monitoring (CGM) devices for detecting hypoglycemia?

Most Accurate CGM Devices for Detecting Hypoglycemia

Real-time continuous glucose monitoring (rtCGM) devices are more accurate than intermittently scanned CGM (isCGM) devices for detecting hypoglycemia, with the Dexcom G6 and G7 showing the highest accuracy in the hypoglycemic range among currently available systems. 1, 2

Accuracy of CGM Systems for Hypoglycemia Detection

• Current CGM devices demonstrate adequate accuracy for euglycemia and hyperglycemia, but accuracy is still inadequate for hypoglycemia detection, although it has improved significantly over time 2
• In a systematic review of commercially available CGM devices, the average mean absolute relative difference (MARD) for overall diagnostic accuracy was 9.4%, with lower accuracy specifically in the hypoglycemic range 2
• None of the devices evaluated with ISO 15197:2013 criteria achieved values ≥95% of measurements in the stipulated ranges for hypoglycemia (±15 mg/dL), though some devices did achieve this standard for hyperglycemia 2
• For hypoglycemia detection, CGM systems demonstrate an average sensitivity of 85.7% and specificity of 95.33% 2

Comparison of CGM Systems

• Real-time CGM (rtCGM) shows superior performance compared to intermittently scanned CGM (isCGM) specifically for hypoglycemia detection, as demonstrated in multiple randomized controlled trials 1
• In two studies with primary outcomes focused on reduction of time spent in hypoglycemia, rtCGM showed clear benefit compared to isCGM 1
• The Dexcom G6 and G7 systems have demonstrated the highest accuracy in the hypoglycemic range among currently available devices 2
• The Veo calibration algorithm (used in Medtronic systems) has shown improved hypoglycemia detection with sensitivity increased from 54.9% to 82.3% (and 90.5% with predictive alerts) 3

Factors Affecting CGM Accuracy in Hypoglycemia

• Accuracy of all CGM devices is lowest in the hypoglycemic ranges, which is a critical limitation since precise detection of low glucose values is essential for patient safety 1
• For the Medtronic CGMS System Gold device, the mean absolute difference between sensor readings and blood glucose readings was 15.0% (12.2%), with accuracy lowest in hypoglycemic ranges 1
• The GlucoDay microdialysis device (Menarini) showed a mean absolute difference of 13.6% (10.2%), also with lowest accuracy in hypoglycemic ranges 1
• In a study of patient-reported symptomatic hypoglycemia, CGM-recorded hypoglycemia according to consensus definition was present in only two-thirds of all patient-reported events when recorded by the Medtronic iPro 2 system 4

Performance Standards for CGM in Hypoglycemia Detection

• CGM devices should safely and reliably provide accurate measurements every 1 to 15 minutes and maintain accuracy over a wide range of glucose values, including the hypoglycemic range 1
• Point accuracy (static blood glucose measurement matching reference) should be similar to that required of intermittent monitoring systems 1
• Rate or trend accuracy (tracking changes in blood glucose concentration) is especially important for hypoglycemia prediction but standards have yet to be fully developed 1
• CGM data should be sufficiently frequent, reliable, and accurate for alarm algorithms to detect and/or predict hypoglycemia with high sensitivity and specificity 1

Clinical Applications and Recommendations

• CGM is particularly useful for patients with hypoglycemia unawareness and/or frequent episodes of hypoglycemia 1, 5
• Despite technological advances, the FDA and clinical guidelines still recommend confirming CGM readings with self-monitoring of blood glucose (SMBG) before making treatment decisions, especially in the hypoglycemic range 1
• Professional CGM can be particularly useful to evaluate periods of hypoglycemia in individuals on agents that can cause hypoglycemia in order to make medication dose adjustments 1
• For patients with frequent hypoglycemia or hypoglycemia unawareness, CGM provides critical information that HbA1c cannot 5

Common Pitfalls and Limitations

• Sensor interference due to medications/substances can affect CGM accuracy, with several substances causing higher sensor readings than actual glucose levels 1
• Contact dermatitis (both irritant and allergic) has been reported with all devices that attach to the skin, which may limit consistent use 1
• CGM devices require calibration and confirmation of accuracy with conventional SMBG, and failure to properly calibrate can lead to inaccurate readings 1
• CGM devices may not detect brief hypoglycemic episodes (less than 15 minutes), potentially missing clinically significant events 4

In conclusion, while CGM technology has improved significantly, there remains a gap in accuracy specifically for hypoglycemia detection. Real-time CGM systems generally outperform intermittently scanned systems for this purpose, with the Dexcom G6/G7 and newer Medtronic systems with improved algorithms showing the best performance for hypoglycemia detection.