A large number of kidneys are discarded every year despite evidence that many could have provided survival benefit for waitlisted candidates. Identifying kidneys at high risk of discard could help facilitate "rescue" allocation to centers that are 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, but it has not been prospectively validated; mechanisms of discard may have changed following policy changes such as the introduction of KDRI and implementation of the Kidney Allocation System (KAS).

METHOD: We prospectively validated the PODD model using SRTR data in the KAS era (1/1/2015-9/1/2017). C-statistics were calculated to assess accuracy in predicting kidney discard. We calculated the center-level probability of accepting kidneys with PODD>0.6 ("high-PODD kidneys") using SRTR match run data 1/1/2015-12/31/2016. The Gini coefficient was used to assess center-level clustering in accepting these high-PODD kidneys.

RESULTS: The C-statistic was 0.86 for PODD indicating excellent predictive ability, for comparison, the c-statistic for KDPI was 0.81. The center-level acceptance of high-PODD offers ranged from 0.0%-15.4% (Figure(a)). Compared to utilization of low-PODD kidneys (Gini coefficient=0.48), utilization of high-PODD kidneys clustered more tightly among a few centers (Gini coefficient=0.86): 135 centers did not accept a single high-PODD offer, and only 20 centers used the majority of high-PODD kidneys (Figure(b)).

CONCLUSIONS: PODD predicted discard risk accurately under KAS. While most centers accepted no high-PODD offers, some centers are willing to accept these kidneys. Preferentially offering high-PODD kidneys to centers that tend to transplant more of these kidneys might help reduce discard of transplantable kidneys.

CITATION INFORMATION: Zhou S., Massie A., Holscher C., Waldram M., Segev D. Prospective Validation of Prediction Models for Kidney Discard Am J Transplant. 2017;17 (suppl 3).

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