Identification of patients at high risk of graft loss by pre- and posttransplant monitoring of anti-HLA class I IgG antibodies by enzyme-linked immunosorbent assay.

Identification of risk factors influencing graft survival may lead to the development of models to predict graft outcome. Such models may provide guidance for immunosuppressive therapy, measure posttransplantation outcome, and eventually improve graft survival in high-risk patients. A major risk factor influencing graft survival is allosensitization. However, due to the lack of standardization of lymphocytotoxicity assays, the detection of alloantibodies utilizing this current methodology may not correlate with posttransplant events. Recently, a novel standardized enzyme-linked immunosorbent assay (ELISA) for the detection of anti-HLA class I IgG antibodies was developed. To evaluate the predictive value of this diagnostic test, a retrospective analysis of 124 renal allograft recipients with an 18-month follow-up time was performed. A highly significant (P=0.01) correlation between pre-transplant ELISA panel reactive antibody (PRA) results and graft loss was observed. Patients with pre-transplant ELISA PRA of >10% had a three times higher risk of graft loss compared with patients who tested negative. No such correlation was observed with complement-dependent cytotoxicity results independent of the reduction of IgM antibodies with dithiothreitol. Similarly, a highly significant correlation of ELISA results with the occurrence of early graft dysfunction was observed. Almost all patients (88%) with a pretransplant ELISA PRA of >50% required posttransplant dialysis, compared with 45% of patients with a pretransplant ELISA PRA of 10-50% and 27% of patients with a pretransplant ELISA PRA of <10%. No such difference was observed with complement-dependent cytotoxicity %PRA values. Analysis of posttransplant specimens by ELISA demonstrated a strong correlation of assay results with graft rejection and graft dysfunction. In summary, these results suggest that detection of anti-HLA class I antibodies by ELISA identifies patients at high risk for graft loss. No other single risk factor of such magnitude has been identified so far.