Making sense of glucose metrics in diabetes: linkage between postprandial glucose (PPG), time in range (TIR) & hemoglobin A1c (A1C)

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© 2021 ELI LILLY AND COMPANY. Published with license by Taylor & Francis Francis Group, LLC.

Table 1. CGM Devices

Device	Type of CGM	Sensor Duration (days)	Number of Calibrations	Information Provided
Medtronic Guardian	Real-time	7	2 per day	Real-time glucose readings Trend arrows Alarms
Dexcom G6	Real-time	10	None	Real-time glucose readings Trend arrows Alarms
Senseonics Eversense	Real-time	90	2 per day	Real-time glucose readings Trend arrows Alarms
Abbott Freestyle Libre	Flash	14	None	Current glucose reading Trend arrow Trend graph depicting latest 8 hours of glucose history
Abbott Freestyle Libre 2	Flash	14	None	Current glucose reading Trend arrow Trend graph depicting latest 8 hours of glucose history Alarms

Figure 1. Identical A1C values, but dramatically different amounts time spent in hypoglycemia and hyperglycemia. Two representative glucose profiles with the same A1C of ~7.0%. The TIR for the representative figures are 40% and 70%. Data from https://diatribe.org/time-range

Abbreviations: TIR, time in range.

Table 2. Consensus CGM Metrics for Clinical Care

Metric	Target
Number of days CGM worn	14 days
Percentage of time CGM is active	70% of data from 14 days
Mean glucose	Not established
Glucose management indicator	Not established
Glycemic variability (%CV)	≤36%*
Time above range: % of readings 181–250 mg/dL	<25% of time above 180 mg/dL
Time above range: % of readings and time >250 mg/dL	<5% above 250 mg/dL
Time in range: % of readings and time 70–180 mg/dL	>70% of the time per day
Time below range: % of readings and time 54–69 mg/dL	<4% time below 70 mg/dL
Time below range: % of readings and time <54 mg/dL	<1% time below 54 mg/dL
[38] Use of AGP for CGM report Abbreviation: CV, coefficient of variation. *Some studies suggest that lower %CV targets (<33%) provide additional protection against hypoglycemia for those receiving insulin or sulfonylureas. [39–41]

Figure 2. Example Ambulatory Glucose Profile Report [38]

Figure 3. A CGM Toolbox for Clinicians. A toolbox to guide clinicians through CGM data analysis. Specifically, (1) Patient-specific data that should be marked on the AGP, (2) Data adequacy, glycemic variability, and Time-in-Ranges targets, (3) nine-step CGM AGP Report Interpretation, and (4) Billing codes are described

Table 3. Patient A and B Demographic Data

	Patient A	Patient B
Weight	202 lbs.	127 lbs.
BMI	36.95 kg/m^2	24.15 kg/m^2
eGFR	>60 mL/min	>60 mL/min
Data Adequacy	15 days	15 days
Average Glucose	136 mg/dL	155 mg/dL
GMI	6.6%	7%
A1C	7.5%	7.5%
Time-in-Ranges
TIR	85%	41%
TAR	14%	37%
TBR	1%	22%
Current Diabetes Medication	Insulin glargine (18 units daily)	Insulin glargine 11 units
	Fixed-dose insulin aspart at mealtimes (5 units with breakfast, 7 units with lunch, and 14 units with dinner)	Glipizide XL 5 mg per day
Abbreviations: BMI, body mass index; eGFR, estimated glomerular filtration rate.

Figure 4. Patient A and B AGP reports at the time of clinic visit. (a) Patient A’s AGP report, and (b) Patient B’s AGP report [38]

Table 4. Patient C Demographic Data

	Patient C
Weight	189 lbs.
BMI	30.56 kg/m^2
Duration of Diabetes	22 years
eGFR	>60 mL/min
Data Adequacy	12 days
Average Glucose	175 mg/dL
GMI	7.5%
A1C	8.7%
Time-in-Ranges
TIR	46%
TAR	44%
TBR	10%
Current Diabetes Medication	Metformin ER (Glucophage XR) 2000 mg at HS
	Liraglutide (Victoza) 1.8 mg at HS
	Insulin glargine (Basaglar) 60 units HS

Figure 5. Patient C AGP reports at the time of clinic visit [38]

Battelino T, Danne T, Bergenstal RM, et al. Clinical targets for continuous glucose monitoring data interpretation: recommendations from the international consensus on time in range. Diabetes Care. 2019;42(8):1593–1603.

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