The clinical significance of flow cytometry crossmatching in heart transplantation - Conference discussion

Objective: Flow cytometry crossmatching (FCXM) is more sensitive than the cytotoxic crossmatch in identifying preformed antibodies to donor alloantigens, but its clinical importance is controversial. The objective of this study was to determine the association of a FCXM with survival and incidence of vascular rejection in cardiac transplant recipients with a negative cytotoxic crossmatch. Methods: Between 1993 and 1998, 357 heart transplant recipients with a negative T cell cytotoxic crossmatch were studied by three-color FCXM to quantitate anti-donor IgG reactions against B and T lymphocytes. Reactions positive against both were consistent with human leukocyte antigen (HLA) Class I reactivity, and those against B cells only were considered to be against HLA Class II antigens. Endpoints were episodes of vascular rejection, death from acute and chronic rejection and overall survival. Results: Fifty patients were FCXM for Class I-positive, 144 for Class II-positive, and 163 were negative. At 1 month, freedom from vascular rejection was 64% in Class I patients, but 90% and 96% in Class II or negative crossmatch patients (P<0.0001). Survival of the negative crossmatch group was higher than either Class I or II groups (94%, 74% and 76%, respectively, at 3 years; P<0.0001). Death from acute rejection was 3% and 2% at 3 years in negative or Class II-positive patients, but 19% in Class I patients (P<0.0001). Death from chronic rejection occurred only in Class II patients (P=0.002). Conclusions: Despite a negative T-cell cytotoxic crossmatch, a positive flow cytometry crossmatch correlates with important clinical events after heart transplantation. Copyright (C) 2000 Elsevier Science B.V.