Evaluation of the permissible mismatch concept

Abstract

Maruya et al. described a method of separating one HLA-A+B+DR mismatched transplants into permissible and immunogenic categories (published in Clinical Transplants 1993). For the permissible subgroup, they observed an outcome similar to that of zero-A+B+DR mismatched transplants. The classification was based on the HLA type combination of donor and recipient. We evaluated this concept with the data of the Collaborative Transplant Study (CTS). We did not obtain significant differences between the outcome of immunogenic and permissible mismatched transplants. The pairwise p-values for the comparison of zero-mismatched with permissible mismatched transplants are significant for cadaver transplants. The indifferent results obtained in our analysis do not support the concept of permissible mismatches. A more restrictive definition of the permissible mismatches might be helpful. The current method appears to be of insufficient reliability due to the relatively small numbers of transplants in the individual subgroups used to identify permissible combinations.