CST3 and chronic kidney disease: Additional subgroup analysis of patients with CKD: A (CKD 1 and 2), B (CKD 3), and C (CKD 4 and 5) showed significant differences in SDMA concentrations between Groups A and B. There were no such results for cystatin C. Both cystatin C and SDMA correlated positively with creatinine in all patients and negatively with eGFR in CKD patients.