Comparison of equations to estimate the glomerular filtration rate in post-renal transplant chronic kidney disease patients

We determined the performance of estimated glomerular filtration rate equations (eGFR) including MDRD2-Isotope Dilution Mass Spectrometry (MDRD2-IDMS),Cockcroft-Gault (CG) and Virga to measure post-transplant chronic kidney disease (CKD) stages 1-4,using simultaneous isotope GFR (iGFR) measurement. The study was conducted in 97 patients. The eGFR results measured by CG and Virga were normalized to 1.73 m 2. Analysis of relative and absolute bias, error, scatter, correlation coefficient of variance and accuracy within the 30% range from the reference iGFR result was performed using standard techniques. There were 135,242,314 and 82 scans,respectively,in CKD stages 1-4. Bias and accuracy of GFR estimators varied significantly across the CKD stages. In stages 1 and 2,CG had the best error of -12.7 and 0.2 mL/min/1.73 m 2,respectively,while Virga had the highest accuracy of 74.3% and 85.5,respectively. In stages 3 and 4,MDRD2-IDMS had the best error of -0.52 and 5.8,respectively. Accuracy was the best at 75.1% for Virga in stage 3,while it was the highest of 70.7% for MDRD2-IDMS in stage 4. Virga had the highest accuracy of 75.2% in stage 4. The worst bias was for MDRD2-IDMS in stage 2 (-36.8 mL/min/1.73 m 2) and the best bias was for CG in stage 2 (-0.33 mL/min/1.73 m 2). The eGFR estimators have inconsistent performances in the various stages of CKD and,thus,another limitation is added to their validity to substitute for the gold standard methods.