The crossmatch may still be the most clinically relevant histocompatibility test performed.

We evaluated patient sera for flow PRA, FCXM, and end-point donor-antigen titer, and we correlated the results with graft survival. You cannot accurately predict a positive or negative FCXM result-not even when the sera have donor-specific antigens-unless you actually perform a crossmatch. Using fluorescence intensity as a surrogate for antibody concentration does not correlate quantitatively with the occurrence of a positive or negative crossmatch. Therefore, it is imperative to give each recipient a chance at being offered a donor organ by performance of a real-time crossmatch and not rely on a virtual evaluation.