Fig. 2

Distribution of CysC proteoforms concentrations across CKD stages in diabetic patients with and without CKD. There are 5 CKD stages based on estimated GFR. Stage 1 is define by eGFR ≥ 90 mL/min/1.73 m² (n = 34), stage 2 is defined by 60 ≤ eGFR ≤ 89 mL/min/1.73 m² (n = 21), stage 3a is defined by 45 ≤ eGFR ≤ 59 mL/min/1.73 m² (n = 6), stage 3b is defined 30 ≤ eGFR ≤ 44 mL/min/1.73 m² (n = 7), stage 4 is defined by 15 ≤ eGFR ≤ 29 mL/min/1.73 m² (n = 7), and stage 5 is defined by eGFR < 15 mL/min/1.73 m² (n = 3). All CysC proteoforms significantly increased across the advanced CKD stages (group ANOVA test). Using pairwise comparisons, des-SSP: stages 1-3b, 1–5, 1–4, 2-3b, 2–4, 2–5; des-S: stages 1–4, 1–5, 2–4, 3a-4; native: stages 1–5 and 1–4 were statistically different. These data suggest that des-SSP and des-S CysC proteoforms increase more robustly by CKD stage compared with native CysC concentrations