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Reevaluation of the Kidney Donor Risk Index

Zhong, Yingchao MS1,2; Schaubel, Douglas E. PhD1,2; Kalbfleisch, John D. PhD1,2; Ashby, Valarie B. MA2; Rao, Panduranga S. MBBS3; Sung, Randall S. MD2,4

doi: 10.1097/TP.0000000000002498
Original Clinical Science—General
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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, we analyzed n = 156069 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.

1 Department of Biostatistics, University of Michigan, Ann Arbor, MI.

2 Kidney Epidemiology and Cost Center, University of Michigan, Ann Arbor, MI.

3 Department of Internal Medicine, University of Michigan, Ann Arbor, MI.

4 Department of Surgery, University of Michigan, Ann Arbor, MI.

Received 21 February 2018. Revision received 8 October 2018.

Accepted 16 October 2018.

The authors declare no conflicts of interest.

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).

Y.Z. participated in research design, literature review, database management, data analysis, writing the article, statistical computing. D.S. participated in research design, database management, data analysis, writing the article. J.K. participated in research design, data analysis, and writing the article. V.A. participated in research design, literature review, data analysis, and writing the article. P.R. participated in research design, literature review, and writing the article. R.S. participated in research design; literature review; writing the article.

Correspondence: Douglas Schaubel, University of Michigan, 1415 Washington Hts., Ann Arbor, MI 48109-2029; (deschau@umich.edu).

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