Precise Measurement of Concentration of Blood Glucose from the Tristimulus Values Obtained from the Colour of the Assay in the Course of Clinical Diagnosis

Abstract

Blood chemical tests carried out in the conventional clinical instruments such as Colorimeter and Spectrophotometer, measure the concentration of the Blood substances such as Glucose, Non-protein nitrogen substances like Amino acids, Peptides, Urea waste and Uric acid, Lipids such as Cholesterol and Triglycerides, Proteins, Enzymes and Steroids, etc. The concentration of these Complex substances appearing in the Blood serum can be analyzed based on colour reactions.This research paper attempts to find an alternative to the 5 decades old Colorimetry based measurement technique. Methods in vogue are fraught with anomalies and deviations because they require a highly monochromatic source; also they possess measurement complexity especially in the non-linear region of the reagent solution. For example, Linearity prevails in the Blood Glucose measurement if the Blood Glucose in the serum is less than 500 mg/dl. As the Colour concentration of the assay increases with that of the Blood chemical in the serum, it is clear that the Wavelength of the Colour of the assay reasonably remains constant irrespective of the concentration of Blood chemical and the variation is only in the saturation of the colour.In the proposed system, the colour image of the assay is captured by a Digital camera connected with a Computer and the RGB data of the colour pixel in that image is converted to its equivalent Tristimulus coordinates (XYZ) and then to Chromaticity coordinates (xyz) of the Chromaticity diagram in conformance with the International Commission on Illumination, CIE 1931, standards of colour space. From the Chromaticity coordinates, the saturation of the colour of the assay can be calculated.The saturations of the colour thus obtained for various known concentrations of Blood chemical are fit into a Polynomial equation of degree ‘m’ This Polynomial equation yields the unknown concentration of the Blood Glucose in the test sample against the saturation of the colour that is calculated from the RGB data. Measurement error is less when the order of polynomial equation is high. As the higher order polynomial equation refines values even in the non-linear region viz., beyond 400 mg/dL, the results obtained from this proposed method are fairly precise. Moreover this proposed method overcomes the shortcomings in the existing system such as requirement of Monochromatic source, Colour development restrictions in the assay (Usually Pink or Purple is preferred).