Table 1.

Summary of the reviewed calibration techniques.

Study	Calibration Technique	Model of BG-IG Dynamic	Real-Time Use in Wearable Devices	Calibrations per Day	Validation Data	Improvements Compared to Manufacturer (if Applicable)
Aussedat et al. [59]	Linear regression with feature to detect phases of steady state signal	No, but use of heuristic technique	Yes	Not specified	Real data from a miniaturized glucose sensor used in rats	/
Knobbe et al. [60,61]	Extended Kalman filter	Yes	Yes	Not specified	Real data from the Medronic (Northridge, CA, USA) MiniMed CGM system	/
Kuure-Kinsey et al. [62]	Dual rate Kalman filter	No	Yes	3	Synthetic data; data from an experimental glucose sensor used in rats	/
Facchinetti et al. [63]	Extended Kalman filter	Yes	Yes	4	Synthetic data	/
Leal et al. [64]	Auto-regressive models	No	Yes	At least 3	Real data from the Medtronic (Northridge, CA, USA) MiniMed CGMS system gold	Median RAD 1 decreased of 4.6%
Leal et al. [65]	Linear regression	No	No	At least 3	Real data from the Medtronic (Northridge, CA, USA) MiniMed CGMS system gold	Median RAD 1 decreased of 2%
Barceló-Rico [66,67]	Multiple local dynamic models [66] with adaptive parameters normalization [67]	Yes	Yes	3–4	Real data from the GlucoDay (Menarini, Florence, Italy) sensor [66]; synthetic data; real data from the Medtronic (Northridge, CA, USA) MiniMed CGMS system gold [67]	MARD 2 decreased of 3.9% in [66] and of 2.4% in [67]
Mahmoudi et al. [68]	Rate-limiting filtering, selective smoothing, and robust regression	No, but use of heuristic technique	Yes	Maximum 4	Real data from SCGM 1 (Roche Diagnostic, Mannheim, Germany) system	/
Kirchsteiger et al. [69,70]	Linear matrix inequalities	Yes	Yes	Roughly 6 (more in day 1)	Real data from the FreeStyle Navigator (Abbott Diabetes Care, Alameda, CA, USA) system	MARD 2 decreased of about 4.7% [70]
Guerra et al. [72]	Linear regression and regularized deconvolution	Yes	Yes	2	Synthetic data; real data from the FreeStyle Navigator (Abbott Diabetes Care, Alameda, CA, USA) and DexCom Seven Plus (Dexcom Inc., San Diego, CA, USA) systems	RMSE 3 decreased of 7.2 mg/dL
Vettoretti et al. [74]	Linear regression and regularized deconvolution	Yes	Yes	2	Real data from the Dexcom G4 Platinum (Dexcom Inc., San Diego, CA, USA) system	MARD 2 decreased of 1.2%
Acciaroli et al. [75]	Linear regression and regularized deconvolution	Yes	Yes	1	Real data from the Dexcom G4 Platinum (Dexcom Inc., San Diego, CA, USA) system	MARD 2 decreased of 1.2%, calibrations reduced from 2 to 1 per day
Acciaroli et al. [76,83]	Multiple-day model and regularized deconvolution	Yes	Yes	0.25 in [76]; zero in [83]	Real data from the Dexcom G4 Platinum (Dexcom Inc., San Diego, CA, USA) system [76] and a next-generation Dexcom prototype [83]	MARD 2 decreased of 1.2%, calibrations reduced from 2 to 0.25 per day [76]
Lee et al. [77]	Linear regression with run-to-run	No	Yes, after a few weeks of CGM use	2	Synthetic data	/
Zavitsanou et al. [78]	Linear regression with weakly updating feature	No	Yes, after a few weeks of CGM use	2	Real data from the Dexcom G4 Platinum (Dexcom Inc., San Diego, CA, USA) system	/
Del Favero et al. [80,81,82]	Linear regression and regularized constrained deconvolution	Yes	No	13 in [80]; 10 in [82]	Real data from the DexCom Seven Plus [80,81] and Dexcom G5 Mobile [82] (Dexcom Inc., San Diego, CA, USA) systems	MARD 2 decreased of 6.9% in [80], of 2.6% and 4.1% in adults and pediatrics in [82]

¹ RAD, relative absolute difference; ² MARD, mean absolute relative difference; ³ RMSE, root mean square error.