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.Methods254 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.ResultsThe rGFR in 254 CKD participants was [ 48.07 (26.19 -92.97 )] ml · min -1·(1.73 m2) -1.The Spearman correlatiou 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.The 95％ confidence intervals for the regression line of 4 eGFRs shown by Bland-Altman graphs were 92.5,87.3,83.0 and 76.1 ml · min-1 · ( 1.73 m2 ) -1,respectively,with the best result of eGFR4.For P30,the correctness of 4 eGFRs were eGFR4 ＞ eGFR3 ＞ eGFR2 ＞ eGFR1,but no significant difference was found by Chi square test (x2 =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 correctnessratewerenotideal(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)
ABSTRACT
ObjectiveTo investigate the impacts of different serum creatinine detection methods,including Jaffe and enzymatic methods,on the efficacy of different GFR estimation equations in CKD patients in China.MethodsrGFR of 176 patients with CKD were determined by dual plasma sample method 99mTc-diethylenetriamine pentaacetic acid (99mTc-DTPA) plasma clearance rate.Serum creatinine was detected with four kinds of creatinine reagents from different manufacturers.Cockcroft-Gault Equation corrected for body surface area (CG/BSA),simplified Modification of Diet in Renal Disease (MDRD) Study equation,IDMS-traceable MDRD equation,CKD epidemiology collaborative research (CKD-EPI) equation and two Chinese simplified MDRD equation (project group equation 1,2) were applied to calculate estimated GFR (eGFR)respectively.eGFRwerecomparedwithrGFRforthecorrelation, deviation, precisionand30％ accuracy.ResultsThe mean rGFR of 176 patients with CKD,was [ 40.70 ( 19.41 -84.35 ) ] ml · min- 1 ·( 1.73 m2 ) -1.For all GFR estimation equations,there were significant differences in eGFR results between enzymatic method and Jaffe method,when analyzed by the Wilcoxon signed-rank test.eGFR results assessed by two enzymatic creatinine detection systems showed no significant difference,while eGFR results analyzed by two Jaffe detection system were significantly different.The intraclass correlation coefficient (ICC) of eGFR and rGFR ranged from 0.879 to 0.923 by Jaffe method,while from 0.925 to 0.946 by enzymatic creatinine method.ICC and Pearson correlation analysis revealed a significant correlation between eGFR and rGFR,and the correlation was better when using enzymatic method.Bland-Altman plots indicated that large deviation occurred in the high value area of GFR using various equations.However,deviation with the enzymatic creatinine method was smaller than that with the Jaffe method. When rGFR ≥ 60 ml · min- 1 ·(1.73 m2) -1,the 30％ accuracy of eGFR using enzymatic creatinine method for all six equations was between 68.3％ and 90.0％,while it was between 41％ and 75％ when using Jaffe method. The 30％ accuracy of eGFR using enzymatic creatinine method was significantly higher than that using picric acid method for these equations except for the project group equation 1.When rGFR ＜60 ml · min -1 · ( 1.73 m2 ) -1,the 30％accuracy of eGFR using both methods was between 39.7％ -49.1％,40.5％ -52.6％respectively,and the difference of data showed no statistical significance.For the same equation,there was a significant differernce in 30％ accuracy of eGFR between two enzymatic creatinine detection systems,while there was no significant differernce between two Jaffe creatinine detection systems.ConclusionsA significant difference was demonstrated in the same GFR evaluation equation using two different creatinine detection methods (Jaffe method and enzymatic method).The correlation between rGFR and eGFR,the degree of deviation,and accuracy of eGFR results assessed by enzymatic creatinine method were better than those by Jaffe method.The eGFR results assessed by different enzymatic detection systems revealed no significant difference.