Relationship of Creatinine and Cystatin C-based Estimated Glomerular Filtration rates with Measured Glomerular Filtration Rate in Healthy Kidney Donors from South Asia

Chronic Kidney Disease-Epidemiology Collaboration (CKD-EPI) equation is currently recommended for the estimation of glomerular filtration rate (GFR). This retrospective study aimed to evaluate the correlation between creatinine and cysC-based estimated GFRs and measured GFR in healthy adults. Consecutive healthy adults who were accepted as voluntary kidney donors at our center between January 2008 and December 2012 were included in the study. The 336 individuals who comprised the study population had a mean age of 41.6 ± 11.8 years, male:female ratio 1:1.7, mean creatinine 0.9 ± 0.1 mg/dl, and mean cysC 0.8 ± 0.1 mg/dl. Mean measured GFR by Tc-99m diethylenetriaminepentaacetic acid using Gates method was 98.4 ± 21.2 ml/min/1.73 m(2). The mean ± standard deviation of eGFRs by various formulae were as follows: Cockcroft–Gault (CG) = 88.1 ± 15.9 ml/min/1.73 m(2), Modification of Diet in Renal Disease (MDRD) = 78 ± 14.7 ml/min/1.73 m(2), CKD-EPI creatinine = 88.1 ± 15.5 ml/min/1.73 m(2), CKD-EPI cysC = 97 ± 19.9 ml/min/1.73 m(2), CKD-EPI creatinine-cysC (CKD-EPI cr-cysC) = 92.5 ± 14.1 ml/min/1.73 m(2). The CKD-EPI cr-cysC equation had the highest accuracy, with 43% and 72% of values lying within ±10% and ±20% of the measured GFR, respectively. Bland–Altman analyses for levels of agreement showed least bias with CKD-EPI cysC overall and among females, while among males, CKD-EPI creatinine equation had the least bias. The CKD-EPI equation showed a higher performance than the MDRD and CG equation in GFR estimation of a healthy population. Among CKD-EPI equations, CKD-EPI cr-cysC had the highest accuracy and CKD-EPI cysC the least bias.