Improved glomerular filtration rate estimation using New equations combined with standardized cystatin C and creatinine in Chinese adult chronic kidney disease patients

Objectives: The newly developed glomerular filtration rate (GFR)-estimating equations developed by the CKD-EPI Collaboration and Feng et al. (2013) that are based on standardized serum cystatin C (ScysC), combined/not combined with serum creatinine (SCT), require further validation in China. We compared the performance of four new equations (CKD-EPIcys, CKD-EPIcr-cys, Feng(cys), and Feng(cr-cys) equations) with the CKD-EPI creatinine equation (CKD-EPIcr) in adult Chinese chronic kidney disease (CKD) patients to clarify their clinical application. Design and Methods: GFR was measured using the dual plasma sampling Tc-99m-DTPA method (mGFR) in 252 adult CKD patients enrolled from four centres. Scr and ScysC were measured by standardized assays in a central laboratory. Each equation's performance was assessed using bias, precision, accuracy, agreement, and correct classification of the CKD stage. Results: The measured GFR was 46 [25-83] mL/min per 1.73 m(2). The CKD-EPIcys, CKD-EPIcr-cys and Feng(cys) equations provided significantly higher accuracy (P-15: 38.9%, 39.7%, and 38.9%) than the CKD-EPIcr equation (29.8%). The CKD-EPIcr-cys and Feng(cr-cys) equations presented higher precision (IQR of the difference, 16.4 and 17.3 mL/min per 1.73 m(2), respectively) and narrower acceptable limits in Bland-Altman analysis (56.6 and 50.8 mL/min per 1.73 m(2), respectively) than single marker-based equations. The CKD-EPIcr-cys equation achieved the highest overall correct proportion (61.5%) in classification of CKD stages. Conclusions: Combining ScysC and Scr measurements for GFR estimation improves diagnostic performance. The Scr-ScysC equation showed better performance than equations based on either marker alone. The CKD-EPIcr-cys equation showed the best performance for GFR estimation in Chinese adult CKD patients. (C) 2014 The Canadian Society of Clinical Chemists. Published by Elsevier Inc. All rights reserved.