A New Kidney Allocation Policy in Chile. Computer Based Simulations

Abstract

Introduction: Kidney allocation involves ethical and technical aspects that have to be addressed in order to reach a balance between fairness, equity and efficiency. Models based on large populations may not be applicable to small countries, so local rules have to be developed and tried before implementation. In Chile kidneys are allocated based on ABO matching, first to medical priorities and then according to a point scheme that considers human leukocyte antigen (HLA) match (60%), time on the waiting list (20%) and panel reactive antibodies (PRA) (20%), additionally paediatric recipients receive extra points. A new policy being developed maintains ABO matching and medical priorities as first step but incorporates several other steps namely prior donors; 0 mismatch recipients; paediatric recipients and finally all other recipients according to a point scheme that incorporates recipient age, HLA match, PRA, and time on waiting list on similar proportions. The aim of this study is to compare the resulting transplants of the new allocation policy to the older. Methods: Computer generated simulations using actual patients (N=1176) on the Chilean waiting list as of September 2011 and 300 donors generated on the previous 3 years, were analyzed. Several simulations were performed randomly distributing the order of the donors in order to eliminate the importance of this factor on the results. Results: The new policy resulted in a significant decrease in the recipient age from 46 years to 41 and an increase in the number of 0 mismatched transplants from 4% to 6%. The mean HLA mismatch increased from 2,51 to 3,19 and HLA DR mismatch from 0,43 to 0,75. Finally waiting time increased from a mean of 40,2 months to 44,3 months. Conclusions: These results support the idea that improvements in the overall quality of transplants being performed can be achieved by changes in allocation policies. With the changes proposed younger patients are being privileged and compatibility is not (exception being made of 0 mismatched donor-recipient pairs). Increase in waiting time observed is probably due to the transplantation of longstanding patients on the wait list that were not candidates previously due to poor matching. Computer generated simulations can help decide which policies are best suited for each country based on their local characteristics.