To discard or not to discard: transplantation and the art of scoring

The growing gap between inadequate supply and constantly high demand for kidney transplantation observed in the last two decades led to exploring the possibility of using organs from older donors with an increasing number of comorbidities. The main issue in this scenario is to identify transplantable organs and to allocate them to the most suitable recipients. A great number of clinical investigations proposed several acceptance/allocation criteria to reduce the discard rate of these kidneys and to improve their outcome, including histological features at the time of transplant. Despite the widespread use of several histological scoring systems, there is no consensus on their value in predicting allograft survival and there is established evidence that histological analysis is the most common reason to discard expanded criteria donor kidneys. To overcome this issue, a clinical scoring system, the Kidney Donor Profile Index (KDPI), was developed on the basis of easily accessible donor features. The KDPI score, adopted in the new US allocation procedure, has good reproducibility but presents several limitations, as suggested also in this issue of Clinical Kidney Journal. This observation should stimulate the search for novel scores combining clinical, histological and molecular features in an attempt to improve the decision process.