Reevaluation of the Kidney Donor Risk Index (KDRI)

Background The Kidney Donor Risk Index (KDRI) is a score applicable to deceased kidney donors which reflects relative graft failure risk associated with deceased donor characteristics. The KDRI is widely used in kidney transplant outcomes research. Moreover, an abbreviated version of KDRI is the basis, for allocation purposes, of the "top 20%" designation for deceased donor kidneys. Data upon which the KDRI model was based used kidney transplants performed between 1995 and 2005. Our purpose in this report was to evaluate the need to update the coefficients in the KDRI formula, with the objective of either (a) proposing new coefficients or (b) endorsing continued used of the existing formula. Methods Using data obtained from the Scientific Registry of Transplant Recipients (SRTR), we analyzed n=156,069 deceased donor adult kidney transplants occurring from 2000 to 2016. Cox regression was used to model the risk of graft failure. We then tested for differences between the original and updated regression coefficients, and compared the performance of the original and updated KDRI formulas with respect to discrimination and predictive accuracy. Results In testing for equality between the original and updated KDRIs, few coefficients were significantly different. Moreover, the original and updated KDRI yielded very similar risk discrimination and predictive accuracy. Conclusions Overall, our results indicate that the original KDRI is robust and is not meaningfully improved by an update derived through modeling analogous to that originally employed. *Corresponding author: Douglas Schaubel, University of Michigan, 1415 Washington Hts., Ann Arbor, MI, 48109-2029; email: deschau@umich.edu Author Contributions: Yingchao Zhong: research design; literature review; database management; data analysis; writing manuscript; statistical computing. Douglas Schaubel: research design; database management; data analysis; writing manuscript. Jack Kalbfleisch: research design; data analysis; writing manuscript. Valarie Ashby: research design; literature review; data analysis; writing manuscript. Pandu Rao: research design; literature review; writing manuscript. Randall Sung: research design; literature review; writing manuscript. Disclosure: The authors have no conflicts of interest to disclose. Funding: This work was supported in part by National Institutes of Health Grant R01 DK070869, and by a Michigan Institute for Clinical and Health Research (MICHR). Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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