Performance of Creatinine and Cystatin C-Based Equations to Estimate Kidney Function in Renal Transplant Recipients

Background: Numerous equations are applied in order to estimate the glomerular filtration rate (GFR). Objectives: This study aimed to spot the optimal equation that accurately estimates GFR and, therefore, the chronic kidney disease (CKD) stage in renal transplant patients. Methods: This cross-sectional study was conducted on 58 renal transplant patients. Their venous blood samples were obtained for serum creatinine and cystatin C determination used to calculate estimated GFR (eGFR). The average contrast of GFR in each equation was calculated using the Bland-Altman method. The correlation, bias, imprecision, and 10% and 30% accuracy were compared between the eGFR cystatin C and creatinine. Concordance between both equations for CKD staging was assessed. The classification of patients was also investigated. Results: Bland-Altman plots and bias demonstrated that eGFR by the abbreviated modification of diet in renal disease (Ab-MDRD) was the most accurate compared with chronic kidney disease epidemiology collaboration (CKD-EPI) cystatin C, followed by CKD-EPI eGFR creatinine. With reference to CKD-EPI cystatin C, the imprecision of the equations was approximately similar to Ab-MDRD, and CKD-EPI creatinine is still better than the Cockcroft-gault (CG) formula. They also showed good 30% accuracy. Finally, our finding suggested that Ab-MDRD and CKD-EPI eGFR creatinine might be the best-performing equation in the classification of the CKD stages in a cutoff of 60 mL/min/1.73 m 2. Conclusions: Due to the high cost and potential delay in measuring cystatin C, it would be much more appropriate to measure Ab-MDRD; after that, CKD-EPI eGFR creatinine as an alternative approach in order to facilitate rapid clinical decision in renal transplant patients.