Relevance of different antibody detection methods for the prediction of antibody-mediated rejection and deceased-donor kidney allograft survival

Presensitizing alloantibodies may represent a grave danger in organ transplantation, increasing the risk of antibody-mediated rejection (AMR) and graft loss. However, not all antibodies are harmful to the graft. In our study of a cohort of 325 deceased-donor renal allograft recipients, the patients were determined eligible to receive an allograft based on a negative complement-dependent cytotoxicity (CDC) crossmatch (XM). Yet at the time of transplantation, many candidates displayed donor-specific antibodies (DSA) by more sensitive methods, such as solid-phase assays (SPA, Luminex) or flow cytometry crossmatch (FCXM). The majority of the patients who were DSA positive by either SPA (67%) or FCXM (66%) presented an AMR-free clinical course posttransplantation. Among the patients who developed AMR (N = 29), 76% proved clinically manageable and did not lose the graft. Analysis of the DSA mean fluorescence intensities (MFI) of Luminex indicated no statistically significant difference between patients who experienced AMR episodes and those who did not. Importantly, many of the patients with AMR did not test positive for DSA by SPA (20/29) or FCXM (14/29). Despite false-positive and false-negative results, the detection of DSA by SPA or FCXM was positively associated with AMR, but not with actuarial graft survival. The field of organ transplantation has always struggled to reconcile two opposing goals: improving transplantation outcome while increasing access to transplantation. SPA and FCXM appear to be oversensitive and defining patients as "sensitized" according to these methods would block access to transplantation for many candidates who would otherwise benefit greatly from receiving the allograft. Nevertheless, SPA and FCXM are invaluable tools, assisting clinicians in gauging AMR risk and tailoring immunosuppression of the posttransplantation immunological monitoring accordingly.