Normal Variate (SNV) normalization of the spectra (See Figure ) allows for a qualitative comparison of the protein composition without considering total protein concentration. In general, the controls from Australia and Spain showed higher intensities of the bands associated with glycoproteins in the 1200-1000 cm⁻¹ region. This indicates that the proportion of albumin relative to the total protein content is higher in the urine of DKD patients, while the control samples exhibit more abundance in glycoproteins (uromodulin). Principal Component Analysis (PCA) was performed on the merged dataset including samples from both countries. The spectra were pre-processed by applying a first derivative followed by mean centering. Only the 3654-2866 cm -1 and the 1786-1012 cm -1 regions were included in the modelling. The PC1 loadings, which explains the 94% of the spectral variance, are depicted in Figure (blue) and correspond with a typical spectrum of albumin, highlighting the Amide I, II and A bands. Control samples have, as expected, lower score values of PC1 than DKD samples (Fig. ). PC2 unfortunately, differentiates DKD samples according to their origin. It can be seen that PC2 decreases concurrently with an increase in PC1 (albumin content) between -0.5 to 0 until a critical point is reached (See Arrows in the x-axis). Notably, Spanish samples reach this inflection point at a lower PC1 value compared to Australian samples (see arrows in Fig. ).