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Prospective Validation of Prediction Model for Kidney Discard

Zhou, Sheng, MD1; Massie, Allan B., PhD1,2; Holscher, Courtenay M., MD1; Waldram, Madeleine M.1; Ishaque, Tanveen, MD1; Thomas, Alvin G.1; Segev, Dorry L., MD, PhD1,2,3

doi: 10.1097/TP.0000000000002362
Original Clinical Science—General

Background. Many kidneys are discarded every year, with 3631 kidneys discarded in 2016 alone. Identifying kidneys at high risk of discard could facilitate “rescue” allocation to centers more likely to transplant them. The Probability of Delay or Discard (PODD) model was developed to identify marginal kidneys at risk of discard or delayed allocation beyond 36 hours of cold ischemia time. However, PODD has not been prospectively validated, and patterns of discard may have changed after policy changes such as the introduction of Kidney Donor Profile Index and implementation of the Kidney Allocation System (KAS).

Methods. We prospectively validated the PODD model using Scientific Registry of Transplant Recipients data in the KAS era (January 1, 2015, to March 1, 2018). C statistic was calculated to assess accuracy in predicting kidney discard. We assessed clustering in centers’ utilization of kidneys with PODD >0.6 (“high-PODD”) using Gini coefficients. Using match run data from January 1, 2015, to December 31, 2016, we examined distribution of these high-PODD kidneys offered to centers that never accepted a high-PODD kidney.

Results. The PODD model predicted discard accurately under KAS (C-statistic, 0.87). Compared with utilization of low-PODD kidneys (Gini coefficient = 0.41), utilization of high-PODD kidneys was clustered more tightly among a few centers (Gini coefficient, 0.84 with >60% of centers never transplanted a high-PODD kidneys). In total, 11684 offers (35.0% of all high-PODD offers) were made to centers that never accepted a high-PODD kidney.

Conclusions. Prioritizing allocation of high-PODD kidneys to centers that are more likely to transplant them might help reduce kidney discard.

1 Department of Surgery, Johns Hopkins University School of Medicine, Baltimore, MD.

2 Department of Epidemiology, Johns Hopkins School of Public Health, Baltimore, MD.

3 Scientific Registry of Transplant Recipients, Minneapolis, MN.

Received 6 April 2018. Revision received 1 July 2018.

Accepted 4 July 2018.

This work was supported by grants K24DK101882 (Segev) and F32DK109662 (Holscher) from the National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) and an American College of Surgeons Resident Research Scholarship (Holscher). The analyses described here are the responsibility of the authors alone and do not necessarily reflect the views or policies of the Department of Health and Human Services, nor does mention of trade names, commercial products, or organizations imply endorsement by the U.S. Government. The data reported here have been supplied by the Minneapolis Medical Research Foundation (MMRF) as the contractor for the Scientific Registry of Transplant Recipients (SRTR). The interpretation and reporting of these data are the responsibility of the author(s) and in no way should be seen as an official policy of or interpretation by the SRTR or the U.S. Government.

The authors declare no conflicts of interest.

D.L.S. and A.B.M. participated in the research design. S.Z., A.B.M., C.M.H., M.M.W., A.G.T., and D.L.S. participated in the writing of the paper. S.Z. and T.I. participated in the data analysis.

Correspondence: Dorry L. Segev, MD, PhD, Department of Surgery, Epidemiology Research Group in Organ Transplantation, Johns Hopkins University, 2000 E. Monument St, Baltimore, MD 21205. (

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