Improving distribution efficiency of hard-to-place deceased donor kidneys: Predicting probability of discard or delay

We recently showed that DonorNet 2007 has reduced the efficiency of kidney distribution in the United States, particularly for those with prolonged cold ischemia time (CIT), by requiring systematic allocation of all kidneys regardless of quality. Reliable early identification of those most likely to be discarded or significantly delayed would enable assigning them to alternate, more efficient distribution strategies. Based on 39 035 adult kidneys recovered for possible transplantation between 2005 and 2008, we created a regression model that reliably (AUC 0.83) quantified the probability that a given kidney was either discarded or delayed beyond 36 h of CIT (Probability of Discard/Delay, PODD). We then analyzed two PODD cutoffs: a permissive cutoff that successfully flagged over half of those kidneys that were discarded/delayed, while only flagging 7% of kidneys that were not eventually discarded/delayed, and a more stringent cutoff that erroneously flagged only 3% but also correctly identified only 34%. Kidney transplants with high PODD were clustered in a minority of centers. Modifications of the kidney distribution system to more efficiently direct organs with high PODD to the centers that actually use them may result in reduced CIT and fewer discards.