Performance of six estimating equations compared with rGFR.

Note: Bias =  median difference between eGFR and rGFR; P30 = the proportion of eGFR within 30% of rGFR; RMSE =  root mean square error.
Abbreviations: rGFR: reference glomerular filtration rate; CI: confidence interval; IQR =  the inter-quartile range of difference; 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.
Wilcoxon matched-pairs signed rank test was used to compare the difference between the eGFR and rGFR (p3); McNemar test was used to compare the P30 of the C-MDRD equation, MacIsaac equation, Ma equation, CKD-EPI2012cys equation and CKD-EPI2012Scr-cys equation against the P30 of CKD-EPI2009Scr equation (p4).