Background: Serum creatinine has been solely used in clinical practice to identify chronic kidney disease (CKD) staging in the elderly population. Serum cystatin C is believed to more accurately define the CKD staging and is also ratified as an endogenous biomarker by Kidney Disease Improving Global Outcomes (KDIGO) guidelines.
Material and methods: A total of 300 elderly Malay participants (age ≥ 65 years) with CKD, attending the Hospital University Sains Malaysia were included in the study. Demographic data and history were also recorded. Serum creatinine was assayed by Chemistry Analyzer Model Architect-C8000 (Jaffe method). While serum cystatin C was examined by Human cystatin C ELISA kit (Sigma-Aldrich) using Thermo Scientific Varioskan Flash ELISA reader.
Results: Out of 300 study participants, 169 (56.3%) were females. Mean age of patients was 67.6 ± 6.7 years. 64 male (64.6%) and 35 female (35.4%) patients were between 70 and 79 years. When estimated by MDRD equation, the prevalence of CKD stage 3 (defined as eGFR = 30 - 59 mL/min/1.73m2) was 27.7%, while based on CKD-EPIcr, CKD-EPIcys, and CKD-EPIcr-cys equations, it was 28%, 36.3%, and 36.3%, respectively. The prevalence of CKD stage 4 (defined as eGFR = 15 - 29 mL/min/1.73m2) when estimated by MDRD was 37.6%, whereas based on CKD-EPIcr, CKD-EPIcys, and CKD-EPIcr-cys equations, it was 36.3%, 46.4%, and 46.4%, respectively. CKD stage 5 (defined as eGFR < 15 mL/min/1.73m2) when estimated by the MDRD equation was 34.7%. While based on CKD-EPIcr, CKD-EPIcys, and CKD-EPIcr-cys equations, the prevalence of CKD stage 5 was 35.7%, 17.3%, and 17.3%, respectively.
Conclusion: The staging of CKD is different between the creatinine- and cystatin C-based equations. Creatinine-based equations classify patients as having CKD stage 5 twice as often as cystatin C-based equations.