Howard M. Gebel, Emory University Hospital, Atlanta, GA, USA.

HLA typing, screening and crossmatching assays are now exquisitely sensitive and specific. Implementation of molecular typing methods has led to the fine resolution of HLA antigens and characterization of allelic variants while the development of solid phase matrices coated exclusively with HLA antigens has permited the identification of HLA antibodies in sensitized patients with exquisite specificity and sensitivity. The advances in HLA technology have resulted in the implementation of the virtual crossmatch (vXM), an in silico approach to classify potential donor:recipient combinations as compatible or incompatible. In brief, the vXM predicts a physical crossmatch to be positive or negative based on whehter the HLA antibodies identified in patient sera using solid phase detection assays correspond to one or more of the HLA antigens present in prospective donors. The implementation of the vXM has proven to be a major step forward in the allocation of deceased donor organs to sensitized recipients.

Learning objectives:

1. To distinguish the difference between a physical and virtual crossmatch
2. To understand the differences between cellular and solid phase antibody detection assays.
3. To understand the concept of cPRA (calculated PRA) in sensitized patients