Utility of the virtual crossmatch in solid organ transplantation

Purpose of review Solid-phase assays covered with single HLA molecules - such as single-antigen flow-beads (SAFBs) - allow determining the presence of donor-specific HLA antibodies (HLA-DSAs) 'virtually' by comparison of the HI-A-antibody specificities of the recipient with the HLA typing of the donor. In this review, prospects and current limitation of the virtual crossmatch are discussed. Recent findings Several prospective and retrospective studies indicate that a negative virtual crossmatch is associated with a very low risk of early rejection and good long-term allograft survival. By contrast, a positive virtual crossmatch is associated with a significant risk for early rejection and decreased allograft survival. However, these studies revealed that not all HLA-DSAs detected by SAFB have a detrimental clinical impact. Summary The virtual crossmatch has emerged as a very useful tool for pretransplant risk assessment and organ allocation. Further advances of the virtual crossmatch approach will require improvements on the technical part of SAFB analysis and a better understanding and definition of pathogenic factors of HLA-DSA. Together with an extended HLA typing of the donor, this scenario will provide us the full benefits of applications based on virtual crossmatching.