Matching "Engine and Chassis" in ECD Kidney Transplantation Using a Novel Creatinine Clearance Match Ratio (CCMR) Is Associated With Improved Outcomes

BACKGROUND: To improve outcomes of expanded criteria donor (ECD) kidneys, prior studies matched donors to recipients according to recipient weight or donor kidney size. This study hypothesizes that matching donors to recipients based on Cockcroft-Gault estimates of creatinine clearance can improve outcomes in ECD kidney transplants compared to predictions based on size matching or donor creatinine clearance alone. METHODS: Recipients of ECD kidneys in the Scientific Registry of Transplant Recipients (SRTR) who were transplanted from October 1, 1987 to August 31, 2011 were included. The estimated creatinine clearance ratio (CCMR) was calculated as the estimated recipient creatinine clearance based on manipulations of the Cockcroft-Gault equation utilizing donor creatinine clearance at the time of transplant. Univariate and multivariate analyses predicted the hazard ratio of graft failure and the odds ratio of requiring dialysis within the first week. The CCMR was compared to the kidney donor risk index (KDRI) and recipient-to-donor weight and age ratios using discrimination analyses. RESULTS: 25,640 ECD kidney transplants were analyzed. On multivariate analysis, higher CCMR was associated with increased graft failure and odds of requiring dialysis within the first week (comparing highest ratio quintile versus lowest ratio quintile: HR 1.53, p<0.001; OR 2.18, p<0.001). CCMR was found to be superior in prediction and discrimination ability as compared to donor creatinine clearance, recipient/donor age ratio, and recipient/donor weight ratio. CONCLUSION: ECD kidneys have improved outcomes when the donor/recipient creatinine clearance match ratio is optimal.