Validation study of chronic kidney disease epidemiology collaboration predictive equations based on serum creatinine and cystatin C in Chinese chronic kidney disease patients

Abstract

Objective To validate the four chronic kidney disease epidemiology collaboration (CKD-EPI) predictive equations based on serum creatinine (SCr) and cystatin C (Cys C) in Chinese CKD patients, and try to develop the GFR predictive equations for Chinese CKD patients. Methods 254 CKD patients were randomly selected from four Grade ⅢA hospitals in different regions in China from September 2007 to December 2010.Clearance of dual plasma sampling 99mTc-DTPA was used to measure glomerular filtration rate (rGFR) in 254 CKD patients.The serum concentration of Cr and Cys C were measured.CKD-EPI SCr equation, Cys C equation, Cys C equation adjusted for age, sex and race, SCr/Cys C combinated equation adjusted for age, sex and race were used to estimate GRF (labeled as eGFR1, eGFR2, eGFR3 and eGFR4, respectively).The correlation, bias and precision of eGFRs were compared with rGFR by Wilcoxon signed rank test, intraclass correlation coefficient (ICC) and Spearman correlation analysis.The deviation degree between rGFR and different eGFRs was compared via Bland-Altman graph.The accuracy within 15%, 25%, 30% (P15, P25, P30) and the staging correctness of eGFR against CKD at different stages was calculated. Results The rGFR in 254 CKD participants was ［48.07(26.19-92.97)］ ml·min-1·(1.73 m2)-1.The Spearman correlation coefficients (CC) of eGFR and rGFR varied within the range of 0.873-0.896 (P=0.000).The intra-class CC (ICC) varied within the range of 0.920-0.942.The correlation of eGFR4 was the best.The absolute deviations of 4 eGFRs and deviation precision were eGFR4 eGFR3>eGFR2>eGFR1, but no significant difference was found by Chi square test (χ2=6.448，P=0.092).The overall correctness rate in 4 eGFRs against CKD stages were 48.4%-57.5%, with the highest consistency of eGFR4, but their staging correctness rate were not ideal (Kappa values were 0.405, 0.348, 0.366 and 0.463, respectively). Conclusions Compared with CKD-EPI SCr equation, no advantage was found in CKD-EPI Cys C equation.The Cys C equation adjusted by age and sex shows a little advantages over CKD-EPI Cys C equation in bias, precision, correlation and accuracy.The CKD-EPI SCr/Cys C combinated equation adjusted by age, sex and race has advantage over other three equations not only in bias, precision, correlation and accuracy, but also in staging correctness.However，the validation of this equation is still not fairly ideal for Chinese CKD patients.Based on these findings, it is essential for the Chinese CKD patients to develop SCr/Cys C combined predictive equation which adjusted by age, sex or other factors.(Chin J Lab Med, 2012，35：798-804) Key words: Glomerular filtration rate; Creatinine; Cystatin C; Renal insufficiency; chronic; Program evaluation; Population surveillance; Algorithms