Dr. Montgomery’s group simulated pools of incompatible donor/recipient pairs and nondirected donors over 24 months, using a clinically detailed model previously described (Am J Transplant. 2005;5:1914-1921). The investigators used an optimization algorithm that picked the best set of two-way and three-way matches for each fixed pool of recipients and donors. For the NEAD chains, they tested various heuristics to ensure that the bridge donor would be likely to match in a future pool.

DPD could allow each nondirected donor to facilitate to an average of 1.9 transplants. NEAD chains could allow for an average of 1.8 transplants for each nondirected donor. Each modality could yield considerably more than the one transplant achieved when a nondirected donor makes a kidney available directly to the waitlist of patients waiting for a deceased donor kidney.

NEAD chains may be a less attractive option than DPD because they shift matches away from traditional KPD to more complex chain arrangements and away from waitlist recipients, without increasing the number of patients transplanted.


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The mode for match arrangements for each NEAD chain over 24 months is one. That means bridge donors would experience long waits before suitable recipients were found. The researchers also found that heuristic strategies of penalizing or disallowing hard-to-match AB-type bridge donors would not increase the utility of NEAD chains.

NEAD chains require a donor to pledge to donate at a future date. NEAD chains also sequester all benefit from nondirected donors to the population of people who have a living donor available, and do not increase the number of recipients transplanted compared with DPD.

“If tomorrow we were able to get all these patients into these programs where they would have access to these types of kidney paired donations, we would probably do an additional 1,500 to 2,000 live donor transplants a year,” Dr. Montgomery said. “That is about a 20% increase. It is dramatic and [would be] the biggest increase in recent decades.”