Fig. 1.

Flowcharts of (a) the conventional implicit and (b) DCC calibration methods. S_calib, c_blood, and s_pred represent the calibration spectra, reference blood glucose concentrations in the calibration samples, and the spectrum acquired from the prediction sample, respectively. For the conventional calibration method, b_conv and c_pred give the regression vector and the predicted concentration, respectively. For DCC calibration, b_DCC represents the developed regression vector. c_ISF,pred and c_blood,pred are the intermediate ISF glucose estimate and the final blood glucose prediction. PC-DCC is the pre-calibration transformation of blood glucose concentrations into the corresponding ISF glucose values. PP-DCC transforms the predicted ISF glucose concentration into the blood glucose value. Note that the conventional calibration scheme does not differentiate between the blood and ISF glucose concentrations.

‡ Both PP-DCC and PC-DCC require two concentration inputs acquired at a time interval Δt apart for evaluation of Eq. (15) and (16), respectively.