Clinical significance of flow cytometry before and after renal transplantation

B-cell crossmatch (BXM) was originally introduced to increase the sensitivity to detect anti-HLA antibodies of conventional CDC crossmatch in renal transplantation. Newer techniques such as Luminex® have greater sensitivity in detecting anti-HLA antibodies but have not been directly evaluated versus BXM. We discuss our experience with Luminex testing and the significance of donor-specific antibodies (DSA) defined by Luminex in three populations, as compared with the CDC crossmatch. In the general transplant population, Luminex-defined DSA were found in only one third of positive CDC-BXM and were associated with graft rejection. Luminex testing enhanced the interpretation of CDC-BXM and identified patients with clinically relevant BXM. In the highly sensitized transplant population, Luminex-defined DSA were found in two thirds of positive BXM and were a better predictor of graft rejection. Therefore, Luminex assays rather than CDC-BXM should be used to facilitate kidney allocation in highly sensitized patients. In the post-transplantation population, Luminex antibody monitoring for DSA was shown to be important, as it defined low-level de novo DSA that were associated with development of transplant glomerulopathy and a significant predictor of graft loss in those patients. Thus Luminex testing facilitated the interpretation of CDC-BXM and provided a useful predictive tool for the detection of clinically significant DSA in post-transplantation antibody monitoring.