With respect to creatinine- and cystatin C-based equations, proteinuria presented better and significant positive correlations with cystatin C and inverse with all cystatin C-based equations (Hoek and cystatin CKD-EPI) and a lower—despite significant—degree of correlation with both creatinine and combined CKD-EPI formulas (Figure 6). This evidence concerns the gene CST3 and chronic kidney disease.