It's not possible. If you really want to make it up,fine, but it was not possible then, it is not possible now."

VOA: standard.2009.07.31

The paper's authors tried to take into account other factors, but they admit it may not have been entirely possible to quantify differences in, for example,the recipient's health, which can be a big factor in the success of a transplant.

VOA: standard.2010.07.14