Table 2.

Inpatient CGM Studies in COVID-19 patients

Reference	Population	Study Design	CGM Used	Study Aim	Results
Faulds et al.[38▪▪]	T1DM (n = 2) T2DM (n = 16) No DM (n = 1) ICU Medicine	Retrospective analysis Single center	Dexcom G6	Feasibility of RT-CGM for insulin infusion titration	- CGM had an overall MARD of 13.9 ± 7.8% (median 11.9, IQR 3.3–29.4) on day 1 and 13.5 ± 8.1% (median 10.6, IQR 9.0–15.0) on days 2 through 7. - Use of CGM resulted in 71% reduction in POC use - Negative association found between BMI and MARD (coefficient = -0.291, P = 0.007).
Chow et al.[42]	DM (n = 30) ICU Medicine	Retrospective study Single center	Dexcom G6	Feasibility and accuracy study of RT-CGM and POC	- 14% reduction in mean glucose during RT-CGM management vs. pre RT-CGM management (235.7 ± 42.1 to 202.7 ± 37.6 mg/dl, P = 0.003). - Use of CGM resulted in 50% reduction in POC use - 63% of nurses reported RT-CGM helped improved clinical care while 49% reported concomitant reduction in PPE use.
Agarwal et al.[36]	T1DM (n = 3) T2DM (n = 6) No DM (n = 2) ICU Medicine	Prospective study Single center	Dexcom G6	Feasibility and accuracy study between CGM and POC	- CGM had an overall MARD of 12.58% and median ARD of 6.3% - Use of CGM resulted in an estimated 60% reduction in POC use
Reutrakul et al.[37]	DM (n = 9) Non-ICU Medicine	Prospective study Single center	Dexcom G6	Feasibility and accuracy study between CGM and POC	CGM had an overall MARD of 9.77%
Sadhu et al.[35]	T1DM (n = 1) T2DM (n = 8) Prediabetes (n = 1) Posttransplant DM (n = 1) ICU Medicine	Retrospective study Single center	Medtronic Guardian Connect Dexcom G6	Feasibility and accuracy study between CGM and POC	- Overall MARD was 13.1% for Medtronic and 11.1% for Dexcom (P = 0.13) - Sensor insertion for both systems were easily done however the Medtronic sensor required more steps as calibration was required when compared to Dexcom. Both systems were noted have a tedious initial setup (i.e., creation of individual accounts on manufacturer's cloud-based platforms)
Ushigome et al. [46]	T2DM (n = 1) Non-ICU Medicine	Case report Single center	Dexcom G4	Feasibility study of RT-CGM for insulin infusion titration	Safe and effective management of hyperglycemia using RT-CGM for insulin infusion without increasing hypoglycemia risk.
Davis GM et al.[44▪]	T2DM (n = 9) ICU Medicine	Prospective study Single center	Dexcom G6	Proof of concept study utilizing hybrid CGM/POC protocol and Glucommander	- During protocol use, 75.7% of sensor glucose values > 100mg/dL were within 20% of the reference POC, with a mean number of POC tests per day of 8.24 ± 3.06 (63% reduction in POC use) - Sensor readings were lower during hypoperfusion states (PEA, shock) and with signal loss during cardiac arrest and defibrillator use. - Sensor accuracy was also impacted during therapeutic hypothermia and position changes including pronation or inadvertent sensor compression.
Shehav-Zaltman et al.[40]	T1DM (n = 1) T2DM (n = 3)	Case series Single center	Medtronic Guardian Connect (Enlite)	Feasibility study of glucose telemetry using Guardian Connect	- Mean daily glucose measurements decreased from 3.75 ± 0.86 to 1.94 ± 0.31 with CGM use (P = 0.005). - Main challenges include training alternating teams with the calibration procedures and cost from weekly replacement of sensors.
Chow et al. [47]	No DM (n = 1)	Case report	Dexcom G6	Feasibility study of RT-CGM for PN-induced hyperglycemia	RT-CGM found to facilitate timely adjustments to insulin infusion in order to achieve target glucose levels.
Garelli et al. [48]	T2DM (n = 3) COVID-19 induced DM (Pediatric) (n = 1) Posttransplant DM (Pediatric) (n = 1) ICU Medicine	Case series Single center	Dexcom G6	Feasibility study of a multipatient, multisite, multi-CGM sensor monitoring platform	- Developed a multipatient platform (Insumate) for simultaneous remote glucose monitoring. - All patients showed improvement in TIR from 12.8% up to 51.65%
Gomez et al.[43]	T2DM (n = 44) No DM (n = 16) Non-ICU & ICU Medicine	Prospective study Single center	Abbot FreeStyle Libre	Examination of glycemic control metrics using CGM	- No differences between the values of TIR, TAR, TBR, CV, or GMI in patients with the composite outcome (ICU admission, ARDS, AKI) - In a subgroup analysis for patients with hyperglycemia without diabetes, higher TAR > 180 mg/dL was seen in patients with AKI (18 vs. 1%, P = 0.01), and in those with the composite outcome (22.5% vs. 16%, P = 0.04)
Longo et al.[39]	T2DM (n = 27) LADA (n = 1) Non-ICU and ICU Medicine	Prospective study Single center	Dexcom G6	Feasibility and accuracy study between CGM, POC, and Lab reference.	- CGM had an overall MARD of 13.2% (12.1% for ICU and 14% for non-ICU). - CGM glucose values showed higher accuracy when compared to glucose Lab reference (MARD 10.9%) than to POC (MARD 13.9%).
Shen et al.[45]	DM (n = 35) Non-ICU Medicine	Prospective study Single center	Abbot Freestyle Libre	Determine the threshold of glycemia and its association with the outcomes of COVID-19	- Patients with composite adverse outcomes (admission to ICU, need for mechanical ventilation, or morbidity with critical illness) had significantly higher TBR (P = < 0.01) than those without composite adverse outcomes. - Mean glucose level was significantly higher in patients with composite adverse outcomes than those without (174 ± 49.0 vs.144 ± 21.2 mg/dL, P < 0.01).

AKI, Acute Kidney Injury; ARD, Absolute Relative Difference; BMI, Body Mass Index; CGM, Continuous Glucose Monitoring; CICU, Cardiac Intensive Care Unit; CV, Coefficient of Variation; DKA, Diabetic Ketoacidosis; DM, Publication did not specify type of Diabetes Mellitus; GMI, Glucose Management Indicator; ICU, Intensive Care Unit; LADA, Latent Autoimmune Diabetes in Adulthood; MAGE, Mean amplitude of glycemic excursions; MARD, Mean Absolute Relative Difference; No DM, No History of Diabetes Mellitus; OR, Operating room; PEA, Pulseless Electrical Activity; PN, Parenteral Nutrition; POC, Point-of-Care Capillary Glucose Testing; PPE, Personal Protective Equipment; RCT, Randomized Control Trial; RT-CGM, Real-Time-Continuous Glucose Monitoring; T1DM, Type 1 Diabetes Mellitus; T2DM, Type 2 Diabetes Mellitus; TAR, Time Above Range; TIR, Time In Range.