A new rapid refractive method based on optical measurements and data processing for the early diagnosis of kidney disease

The need to develop a new reliable and easy-to-implement method for the real-time monitoring of parameters of biological fluids to solve various problems in medicine, biology and related fields is substantiated. We propose a new method for determining parameters of biological fluids using optical and refractometric measurements and a new data processing technique. The operating principle of the new method is exemplified by the express monitoring of characteristics of a human urine sample. Using measurements of the refractive index n at different wavelengths of laser light and derived calibration coefficients, the density, osmolarity, size of protein compounds and concentration of solid particles in the sample are determined. The suitability of the developed method for reliably determining the aforesaid four parameters from the measured values of n in the temperature range from 15 to 32 °C is confirmed. This allows additional data to be obtained for determining calibration coefficients, enabling the determination of density, osmolarity, protein size and solids concentration with an error of less than 0.5% based on the measured values of n at four laser wavelengths using a single device (refractometer). In industrial devices for express monitoring of osmolarity and density, the measurement accuracy is lower; the remaining two parameters are measured only using laboratory instruments. To implement the proposed method, the design of a refractometer operating on the phenomenon of total internal reflection is modernized and an experimental goniometer-based setup is developed. Results of the express testing of urine samples are presented.