Agreement between Creatinine and Cystatin C-Based Equations in the Estimation of Glomerular Filtration Rate among Malaysian Patients with Renal Impairment

Background: Cystatin C-based equations have been proposed as an alternative for creatinine-based equations in the estimation of Glomerular Filtration Rate (eGFR). Limited studies were available with regards to the Asian population to evaluate the agreement of eGFR measured based on both biomarkers. This study aimed to evaluate the agreement between various cystatin C- and creatinine-based eGFR equations. Methods: Patients were recruited from the Nephrology Clinic Universiti Kebangsaan Malaysia Medical Centre. Serum cystatin C and creatinine levels were analysed by particle-enhanced immunoturbidimetry assay and kinetic alkaline picrate method, respectively. Various cystatin C-based (Hoek, Larsson, Grubb, Flodin, cystatin C-based Chronic Kidney Disease Epidemiology (CKD-EPI)) and creatinine-based eGFR equations (Cockcroft-Gault, Modification of Diet in Renal Disease, creatinine-based CKD-EPI) were compared by using the Pearson's correlation and Bland-Altman plot. Results: A total of 118 patients included in this study have a mean age of 61 +/- 15 years and 57.6% were female. The mean serum cystatin C and creatinine levels were 2.00 +/- 1.06 mg/L and 2.21 +/- 1.63 mg/dL, respectively. The correlation between serum cystatin C and creatinine level was significant (r = 0.78, P < 0.01). All cystatin C-based eGFR correlated significantly with the creatinine-based eGFR equations. The strongest correlation was between creatininebased and cystatin C-based CKD-EPI equation (r = 0.93, P < 0.01). The Bland-Altman plot shows that cystatin C-based CKD-EPI equation had the least mean difference when compared with creatinine-based CKD-EPI equation. Conclusion: Significant correlation and good agreement were demonstrated between various cystatin C-based and creatininebased eGFR equations. The cystatin C-based equations are appropriate alternative for GFR measurement among Malaysian patients with renal impairment.