Renal transplantation and HLA-A,B matching. Theoretical considerations concerning pool size

The rate of improvement in HLA matching quality with increasing pool size is predicted. The expected frequency of HLA-A,B-compatible matches increases rapidly up to approximately 47% for pool size 1,000 and from then on the increase is moderate, whereas for HLA-A,B-identical matches the increase in frequency is more constant, the expected frequencies being approximately 34 and 52% for pool sizes 1,000 and 2,500, respectively. The expected frequency of HLA-A,B fullhouse-identical matches is 33% at a pool size of 2,500. The waiting time for the first available HLA-identical kidney is estimated. For a random recipient there is a 25% chance of obtaining an HLA-identical match among the first 500 kidney donors. For two cooperating pools, it is calculated at which relative transplantation activity the kidney import to export is balanced and also the decrease in waiting time for an identical match when cooperating is estimated. The results of a kidney exchange simulation are presented and they agree well with the theoretical considerations.