Regression analysis of the difference between eGFR and rGFR against the average of eGFR and rGFR.

Note: The slope of the regression line against the X axis stands for the bias for eGFR; the trend of accuracy for eGFR was expressed as the intercept of the regression line against the Y-axis. The difference between eGFR and rGFR was regressed against the average of eGFR and rGFR. X-axis represented the average of eGFR and rGFR. Y-axis represented the difference between eGFR and rGFR.Abbreviations: eGFR: estimated glomerular filtration rate; rGFR: reference glomerular filtration rate; CI: confidence interval; C-MDRD: the Chinese modified Modification of Diet in Renal Disease equation; CKD-EPI: Chronic Kidney Disease Epidemiology Collaboration; CKD-EPI2009Scr: serum creatinine–based CKD-EPI equation which was developed in 2009; CKD-EPI2012cys: cystatin C–based CKD-EPI equation which was newly developed in 2012; CKD-EPI2012Scr-cys: serum creatinine– and cystatin C–based CKD-EPI equation which was newly developed in 2012.ANCOVA test was used to compare the slopes (p5) and intercepts (p6) of the regression line of the C-MDRD equation, MacIsaac equation, Ma equation, CKD-EPI2012cys equation and CKD-EPI2012Scr-cys equation against the slope and intercept of CKD-EPI2009Scr equation.