Prospective Validation of Prediction Model for Kidney Discard

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 following 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 SRTR data in the KAS era (1/1/15-3/1/18). C statistic was calculated to assess accuracy in predicting kidney discard. We assessed clustering in center's utilization of kidneys with PODD>0.6 ("high-PODD") using Gini coefficients. Using match run data 1/1/15-12/31/16, we examined distribution of these high-PODD kidneys offered to centers that never accepted a high-PODD kidney. Results PODD predicted discard accurately under KAS (C-statistic=0.87). Compared to 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 11,684 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. Correspondence Information: Dorry Segev, M.D., Ph.D., Marjory K. and Thomas Pozefsky Professor of Surgery and Epidemiology, Associate Vice Chair, Department of Surgery, Director, Epidemiology Research Group in Organ Transplantation, Johns Hopkins University, 2000 E. Monument Street, Baltimore, MD 21205, 410-502-6115 (tel) 410-614-2079 (fax). dorry@jhmi.edu Authorship Dorry Segev and Allan Massie participated in the research design. Sheng Zhou, Allan Massie, Courtenay Holscher, Madeleine Waldram, Alvin Thomas, and Dorry Segev participated in the writing of the paper. Sheng Zhou and Tanveen Ishaque participated in the data analysis. Disclosure The authors declare no conflicts of interest. Funding This work was supported by grants number 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. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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