Al Roth, Utku Unver and Tayfun Sonmez are economists who study matching markets:  mechanisms for linking buyers and sellers.  They have for the last few years been involved in a remarkable project which utilizes the ideas from matching markets to improve the way kidney donors are matched with patients who need kidney transplants.  Traditionally there have been only a few ways in which these transplants were made possible:

  1. a patient’s family member with matching tissue characteristics donates a kidney.
  2. a patient receives a kidney from an altruistic donor with matching tissue characteristics.
  3. two patients who have family members willing to donate but whose tissue characteristics match only the other patient have four simultaneous operations to transplant the kidneys from patient A’s family member to patient B and from patient B’s family member to patient A.

1. is unlikely because there are a surprisingly high number of characteristics that have to match.  2. happens but there is a very long queue of kidney patients waiting for donors and many patients die before reaching the top of the queue and finding a matching donor.  (On top of that, waiting around on artifiicial kidney dialysis = suffering.)  The possibility of 3 improves the chances of a succesful transplant for many.

What these authors did was to point out the tremendous increase in the potential number of successful transplants that would arise if longer chains of transplantation were allowed and suggested mechanisms for matching patients along long chains where a donor gives to a patient who has a family member whose tissue matches with another patient who has a family member whose tissue matches… eventually returning to a family member of the original donor.  Even better, if the original donor is an altruist, one fewer constraint has to be satisfied.

Well, today it was announced that the longest donor chain in history was just succesfully carried out:  10 patients long. Here is a link to the announcement on Al Roth’s blog.