Beyond A1C-Standardization of Continuous Glucose Monitoring Reporting: Why It Is Needed and How It Continues to Evolve

Abstract

Continuous glucose monitoring (CGM) systems are becoming part of standard care for type 1 diabetes, and their use is increasing for type 2 diabetes. Consensus has been reached on standardized metrics for reporting CGM data, with time in range of 70-180 mg/dL and time below 54 mg/dL recognized as the key metrics of focus for diabetes management. The ambulatory glucose profile report has emerged as the standard for visualization of CGM data and will continue to evolve to incorporate other elements such as insulin, food, and exercise data to support glycemic management.

FIGURE 1

Case 1 AGP report interpretation. Patient history: Type 2 diabetes on metformin 1,000 mg twice daily, once-weekly glucagon-like peptide 1 receptor agonist, and 80 units insulin glargine at night. Quick analysis: Panel 1. Ask: Is action needed? Answer: Yes, both TIR and time below range (TBR) are not at target. TIR = 46% (target >70%); TBR (Low + Very Low) = 10% (target <4%); and TBR (Very Low) = 5% (target <1%). Panel 2. Ask: Where is action needed? Address hypoglycemia first. Note that from 4:00 to 8:00 a.m., 25% of values are <70 mg/dL, and from 3:00 to 6:00 a.m., 5% of values are <54 mg/dL. Note the classic “stair-step” pattern of postmeal elevations associated with overbasalization (continued titration of basal insulin without attaining glycemic targets). Panel 3. This graphic representation of data confirms low and high glucose occurring on both weekends and weekdays. Plan: Reduce basal insulin (we went to 36 units of glargine) and add premeal rapid-acting insulin (14 units at breakfast, 10 units at lunch, and 12 units at dinner). Also, work on consistency of food intake and exercise to address the considerable glucose variability.

FIGURE 2

Case 2 AGP report interpretation before and after lifestyle intervention. Patient history: Type 2 diabetes with history of cardiovascular disease on metformin 1,000 mg twice daily and once-weekly glucagon-like peptide 1 receptor agonist. A) Initial AGP before lifestyle intervention. Quick analysis: Panel 1. Ask: Is action needed? Answer: Yes, TIR = 55% (target >70%), TBR = OK. Panel 2. Ask: Where is action needed? The entire glucose curve needs to shift down, and each postmeal excursion needs to be reduced, particularly after lunch. Plan: Initiation of a basal insulin was considered to shift the glucose curve down or the addition of a sodium–glucose cotransporter 2 inhibitor to minimize glucose excursions, but the patient wanted to try changing food intake. The patient was given the International Diabetes Center’s CGM Lifestyle Choices guide (http://www.agpreport.org/agp/learning). B) Follow-up AGP after lifestyle intervention. Follow-up AGP was markedly improved. TIR increased from 55 to 78% with no hypoglycemia of concern. The patient stated that he stopped drinking sugar-containing beverages (particularly at lunch), used the plate method of meal planning, and increased his daily walking, demonstrating that, with some guidance and support, CGM can facilitate helpful lifestyle changes.