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

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ORIGINAL ARTICLE


Year : 2012 \| Volume : 23 \| Issue : 3 \| Page : 453-460

Comparison of equations to estimate the glomerular filtration rate in post-renal transplant chronic kidney disease patients Ahmed Attia¹, Ahmed Zahran², Ahmed Shoker³ ¹ National Liver Institute, Menoufiya University, Egypt ² Nephrology Unit, Department of Medicine, Menoufiya University Hospital, Menoufiya University, Egypt ³ Saskatchewan Transplant Program, St. Paul's Hospital, Saskatoon, Canada Correspondence Address: Ahmed Shoker Director of Transplant Program, Department of Medicine, Division of Nephrology, University of Saskatchewan, 103 Hospital Drive, Saskatoon, SK S7N 0W8 Canada

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.



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