Near-Infrared Spectroscopy Based on Portable Instrument for the Assessment of Glucose Concentration: In Vitro Experiments

The measurement of glucose levels in patients under life-saving treatments, such as hemodialysis, is clinically important. In fact, during hemodialysis patients with type 2 diabetes may be at risk for hypoglycemic episodes. Even in non-diabetic patients, glycemia monitoring during hemodialysis is relevant, due for instance to its relationships with sodium (whose appropriate balance is crucial in hemodialysis). The measurement of glucose during hemodialysis can be performed with traditional methods, but this requires consumables, and operator intervention. Possible glucose measurement in the extracorporeal hemodialysis circuit (in plasma and/or dialysate) through optical methods may allow continuous and operator-free measurement. We aimed exploring the Near-Infrared approach, through a portable spectrometer. We analyzed deionized water samples at increasing glucose concentrations: 50, 100, 150, 200, 300, 500 mg/dl. For increased accuracy, we assessed separately the difference in transmittance between each pair of concentration values, with the lower value taken as reference. For each comparison, every experimental step was repeated twice and eventually average value taken. We used the DWARF-Star Miniature NIR Spectrometer by StellarNet, with detector for the 1000-1700 nm range. We found that the spectral range with more marked differences between the tested glucose concentrations was similar in each pair of concentration values: around 1300-1450 nm. The highest percentage transmittance difference was 3.44% in 50-100 mg/dl pair of values, 2.09% in 100-150, 1.80% in 150-200, 2.40% in 200-300, 3.44% in 300-500. Notably, these difference values were higher than the variability observed between the repeated measures performed for each glucose concentration. In conclusion, we showed that, with a portable, relatively inexpensive spectrometer, glucose concentration may be detected through variations in specific portions of the Near-Infrared band.