title: Improved glomerular filtration rate estimation using new equations combined with standardized cystatin C and creatinine in Chinese adult chronic kidney disease patients.
abstract: OBJECTIVE
  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 (Scr), require further validation in China. We compared the performance of four new equations (CKD-EPIcys, CKD-EPIcr-cys, Fengcys, and Fengcr-cys equations) with the CKD-EPI creatinine equation (CKD-EPIcr) in adult Chinese chronic kidney disease (CKD) patients to clarify their clinical application.
  
  
  METHODS
  GFR was measured using the dual plasma sampling (99m)Tc-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 Fengcys equations provided significantly higher accuracy (P15: 38.9%, 39.7%, and 38.9%) than the CKD-EPIcr equation (29.8%). The CKD-EPIcr-cys and Fengcr-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.
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Xiuzhi
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Nephrology, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Qin
authors.affiliation: Department of Nephrology, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Ke
authors.initials: K
authors.lastname: Zheng
authors.affiliation: Department of Nephrology, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Mengchun
authors.initials: M
authors.lastname: Gong
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Jie
authors.initials: J
authors.lastname: Wu
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Weiling
authors.initials: W
authors.lastname: Shou
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Xinqi
authors.initials: X
authors.lastname: Cheng
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Liangyu
authors.initials: L
authors.lastname: Xia
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China.
authors.forename: Ermu
authors.initials: E
authors.lastname: Xu
authors.affiliation: Department of Nephrology, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China. Electronic address: 0605.mei@gmail.com.
authors.forename: Xuemei
authors.initials: X
authors.lastname: Li
authors.affiliation: Department of Laboratory Medicine, Peking Union Medical College Hospital, Chinese Academic Medical Science and Peking Union Medical College, Beijing, P. R. China. Electronic address: lingqiubj@aliyun.com.
authors.forename: Ling
authors.initials: L
authors.lastname: Qiu
mesh_terms: D000328:Adult; D044466:Asian People; D015415:Biomarkers / Q000097:blood; D002681:China; D003404:Creatinine / Q000097:blood*; D055316:Cystatin C / Q000097:blood*; D005260:Female; D005919:Glomerular Filtration Rate / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D012015:Reference Standards; D051436:Renal Insufficiency, Chronic / Q000097:blood* / Q000503:physiopathology*
chemical_list: D015415:Biomarkers; D055316:Cystatin C; D003404:Creatinine
keywords: Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI); Chronic kidney disease; Creatinine; Cystatin C; Glomerular filtration rate