The clinical significance of flow cytometry crossmatching in heart transplantation

Objective: Flow cytometry crossmatching (FCXM) is more sensitive than the c ytotoxic crossmatch in identifying preformed antibodies to donor alloantige ns, but its clinical importance is controversial. The objective of this stu dy was to determine the association of a FCXM with survival and incidence o f vascular rejection in cardiac transplant recipients with a negative cytot oxic crossmatch. Methods: Between 1993 and 1998, 357 heart transplant recip ients with a negative T cell cytotoxic crossmatch were studied by three-col or FCXM to quantitate antidonor IgG reactions against B and T lymphocytes. Reactions positive against both were consistent with human leukocyte antige n (HLA) Class I reactivity, and those against B cells only were considered to be against HLA Class II antigens. Endpoints were episodes of vascular re jection, death from acute and chronic rejection and overall survival. Resul ts: Fifty patients were FCXM for Class I-positive, 144 for Class II-positiv e, and 163 were negative. At 1 month, freedom from vascular rejection was 6 4% 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 yea rs; P < 0.0001). Death from acute rejection was 3% and 2% at 3 years in neg ative or Class II-positive patients, but 19% in Class I patients (P < 0.000 1). Death from chronic rejection occurred only in Class II patients (P = 0. 002). Conclusions: Despite a negative T-cell cytotoxic crossmatch, a positi ve flow cytometry crossmatch correlates with important clinical events afte r heart transplantation. (C) 2000 Elsevier Science B.V. All rights reserved .