Non-invasive blood glucose monitoring by means of near infrared spectroscopy: investigation of long-term accuracy and stability

Modern strategies in the treatment of Diabetes mellitus require frequent bl ood glucose tests. Near-infrared spectroscopy [NIR] is considered to be a m ethod for non-invasive blood glucose testing. The present study evaluated t he long-term accuracy and stability of the method. Spectra of 10 patients w ere recorded. An individual calibration models were calculated for each pat ient from spectra which were recorded at the beginning of the investigation . These models were then applied to calculate blood glucose values from spe ctra which were recorded 84 to 169 days later. The longterm accuracy and st ability of the calibration models er;pressed as root mean squared error of prediction [RMSP] varied from 3.1 to 35.9 mmol/l and the error grid analysi s [EGA] from 13 to 92% clinically acceptable values in zones A and B. The r esults of the investigation indicate that long-term monitoring of blood glo cose by means of NIR-spectroscopy and individual calibration models over a period of 3 to 4 months is basically possible once long-term stability of t he method will be improved. Further technological progress and a better und erstanding of the underlying physiological processes is necessary to achiev e a level of accuracy reliability and stability of the method as required f or clinical application.