Comparison of Abbreviated Modification of Diet in Renal Disease Formula (aMDRD) and the Cockroft–Gault Adjusted for Body Surface (aCG) Equations in Stable Renal Transplant Patients and Living Kidney Donors

Abstract

The performance of abbreviated Modification of Diet in Renal Disease formula (aMDRD) and the Cockroft–Gault adjusted for body surface (aCG) equations as compared with measured 125I-iothalamate glomerular filtration rate was analyzed in patients with stable renal transplantation (RTx) and in potential living kidney donors (LKD). One hundred and thirty-one patients had RTx and 150 were LKD. The paired t-test showed that the estimated glomerular filtration rate (GFR) values through the aMDRD and the corrected CG equations were significantly different from each other (p < 0.01). There were significant differences between GFRs estimated using aCG and aMDRD equations (p < 0.001) in both groups (RTx and LKD) of different ages. The Pearson correlation coefficient between aCG and aMDRD equations was good (0.77, p < 0.01), but the kappa coefficient was 0.39, indicating a low agreement between the two formulae. In RTx patients with GFR <60 mL/min/1.73 m2, the aMDRD equation performed better than the aCG formula with respect to bias (–0.6 vs. 3.0 mL/min/1.73 m2, respectively) and accuracy within 30% (72% vs. 56%, respectively) and 50% (91% vs. 73%, respectively). Similar results are reported for 48 diabetic RTx patients. In the LKD, the aMDRD equation significantly underestimated the measured GFR when compared with the aCG formula, with a bias of –8.0 versus 2.2 mL/min/1.73 m2, respectively (p < 0.05). We can conclude that the Cockroft and MDRD equations cannot be used interchangeably in clinical transplantation practice and in order to adjust drug doses.