Is the Chronic Kidney Disease Epidemiology Collaboration creatinine–cystatin C equation useful for glomerular filtration rate estimation in the elderly?

BACKGROUND We aimed to evaluate the performance of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine-cystatin C equation in a cohort of elderly Chinese participants. MATERIALS AND METHODS Glomerular filtration rate (GFR) was measured in 431 elderly Chinese participants by the technetium-99m diethylene-triamine-penta-acetic acid ((99m)Tc-DTPA) renal dynamic imaging method, and was calibrated equally to the dual plasma sample (99m)Tc-DTPA-GFR. Performance of the CKD-EPI creatinine-cystatin C equation was compared with the Cockcroft-Gault equation, the re-expressed 4-variable Modification of Diet in Renal Disease (MDRD) equation, and the CKD-EPI creatinine equation. RESULTS Although the bias of the CKD-EPI creatinine-cystatin C equation was greater than with the other equations (median difference, 5.7 mL/minute/1.73 m(2) versus a range from 0.4-2.5 mL/minute/1.73 m(2); P<0.001 for all), the precision was improved with the CKD-EPI creatinine-cystatin C equation (interquartile range for the difference, 19.5 mL/minute/1.73 m(2) versus a range from 23.0-23.6 mL/minute/1.73 m(2); P<0.001 for all comparisons), leading to slight improvement in accuracy (median absolute difference, 10.5 mL/minute/1.73 m(2) versus 12.2 and 11.4 mL/minute/1.73 m(2) for the Cockcroft-Gault equation and the re-expressed 4-variable MDRD equation, P=0.04 for both; 11.6 mL/minute/1.73 m(2) for the CKD-EPI creatinine equation, P=0.11), as the optimal scores of performance (6.0 versus a range from 1.0-2.0 for the other equations). Higher GFR category and diabetes were independent factors that negatively correlated with the accuracy of the CKD-EPI creatinine-cystatin C equation (β=-0.184 and -0.113, P<0.001 and P=0.02, respectively). CONCLUSION Compared with the creatinine-based equations, the CKD-EPI creatinine-cystatin C equation is more suitable for the elderly Chinese population. However, the cost-effectiveness of the CKD-EPI creatinine-cystatin C equation for clinical use should be considered.