Out with the old, in with the new: Virtual versus physical crossmatching in the modern era

The virtual crossmatch (VXM) is gaining acceptance as an alternative approach to assess donor:recipient compatibility prior to transplantation. In contrast to a physical crossmatch, the virtual crossmatch does not require viable donor cells but rather relies on complete HLA typing of the donor and current antibody assessment of the recipient. Thus, the VXM can be performed in minutes which allows for faster transplant decisions thereby increasing the likelihood that organs can be shipped across significant distances yet safely transplanted. Here, we present a brief review of the past 50 years of histocompatibility testing; from the original complement-dependent cytotoxicity crossmatch in 1969 to the new era of molecular HLA typing, solid-phase antibody testing and virtual crossmatching. These advancements have shaped a paradigm shift in our approach to transplantation. That is, foregoing a prospective physical crossmatch in favor of a VXM. In this review, we undertake an in-depth analysis of the pros- and cons- of physical and virtual crossmatching.Finally, we provide objective data on the selected use of the VXM which demonstrate the value of a VXM in lieu of the traditional physical crossmatch for safe and efficient organ transplantation.