From Hero to Zero: A Single Center Retrospective Review of the Utility of Routine Physical Crossmatching.

Abstract

Pre-transplantation HLA antibody testing is necessary to assess compatibility between donor and recipient pairs. Over the past decade, the virtual crossmatch (VXM) has replaced the physical crossmatch (PXM) as the main assessment of pre-transplant histocompatibility. At our center, most transplants have proceeded based solely on the VXM, followed by a retrospective PXM. In this study, we sought to determine whether VXMs alone are sufficient and if routine retrospective PXMs can be discontinued. A review of PXMs for single solid organ transplant cases between 5/19/2020 and 12/9/2022 was performed to examine the concordance between the PXM and VXM (including predictions of the PXM made in the VXM report). The relationship between PXM results (PXMR) and donor specific antibody (DSA) mean fluorescence intensity (MFI) values was also examined. The overall PXM prediction/PXM result concordance rate was 99.7% based on PXMs attributed to HLA antibody. Furthermore, DSA MFI values can guide clinical decisions on whether to perform a PXM. The data confirm that, in the era of the VXM, routine PXMs performed for all transplants are not warranted. However, a PXM may still be informative in select cases where low-to-intermediate strength DSAs are present or when the virtual assessment is ambiguous.