11: CGM Accuracy (Part 2): Understanding MARD, 20/20, 40/40, and Error Grids.

In this episode of the Glucose Never Lies podcast, hosts John Pemberton and Louise discuss the intricacies of diabetes management, focusing on continuous glucose monitoring (CGM) systems. They explore the importance of CGM accuracy, the standards set by regulatory bodies, and the significance of testing conditions in evaluating these devices. The conversation delves into various metrics used to assess CGM performance, including MARD, 20/20 and 40/40 agreement rates, and highlights the need for robust testing against capillary glucose to ensure effective diabetes management. The episode emphasises the importance of transparency in CGM studies and the future directions for standardizing testing protocols.

takeaways

• CGM systems are crucial for real-time glucose monitoring.
• FDA standards are currently the highest for CGM performance.
• CE marking does not guarantee device accuracy or reliability.
• Testing conditions significantly impact CGM accuracy results.
• The 20/20 standard indicates no risk for insulin dosing decisions.
• The 40/40 metric identifies high-risk readings in CGM data.
• Robust testing against capillary glucose is essential for accuracy.
• Standardization in CGM testing is needed for better diabetes management.
• Transparency in CGM studies is vital for healthcare professionals and patients.

00:00
Introduction to Diabetes Management and Podcast Goals

02:07
Understanding Continuous Glucose Monitoring (CGM) Systems

06:08
Evaluating CGM Accuracy and Performance Standards

10:09
The Importance of Testing Conditions in CGM Studies

14:13
Metrics for Assessing CGM Accuracy

18:03
Comparing CGM Systems Against Capillary Glucose

22:02
Future Directions for CGM Testing and Standards

Key Resources

CGM Series: Assessing CGM Accuracy Performance

Chart for CGM Devices (From May 2025): DSN Forum

Tim Street @ Diabettech