B-Cell crossmatching and kidney allograft outcome in 9031 United States transplant recipients.

The predictive power of a positive B-cell crossmatch remains controversial due to the presence of cofactors, such as sensitization and human leukocyte antigen (HLA) mismatch levels. UNOS OPTN/Scientific Registry data were analyzed on 9031 cadaveric kidney graft recipients who were B-cell crossmatched during 1994 and 1995 for graft outcome. This 2-year time period was chosen so that most US transplant recipients in this study would have had a similar regimen of immunosuppression consisting of prednisone, Sandimmune, and azathioprine The two patient groups that were analyzed were B-pos (n = 336) and B-neg (n = 8,695). All T-cell crossmatches were negative. Data analyzed included donor-recipient demographics, sensitization levels, B-cell crossmatch techniques, histocompatibility mismatching, graft rejection incidence, early graft loss, cause of graft failure, and statistical analyses (univariate and multivariate) in primary and repeat graft recipients. Significant factors in both crossmatch groups included pretransplant transfusions, peak and most recent class I PRA levels, a previous kidney graft, histocompatibility mismatching at HLA-A plus -B, urine in first 24 h, and rejection incidence between discharge and 6 months post-transplantation. Class II antibody specificities and panel reactive antibody (PRA) levels were not available from the UNOS database. Fifty-seven percent of 15,896 (1994-1995) transplant recipients (n 9031) were B-cell crossmatched, and 336 of 9031 recipients (3.7%) were transplanted with a B-pos crossmatch. Sixteen percent of B-pos recipients experienced early graft loss (< 6 months) compared with 11% of B-neg recipients (p < 0.001). Both primary and repeat grafts with B-pos crossmatches experienced an increase in rejection incidence (p = 0.023) and early graft loss (p < 0.001). In the sensitized (PRA > 10%) recipient subset (n = 2,789), both primary (n = 93) and regraft (n = 52) recipients with B-pos crossmatches had a higher incidence of early graft loss at 3 months, p < 0.001 and p = 0.016, respectively. HLA-DR mismatch levels in both patient groups were not different (p = 0.109). There was a 68% increase in the odds of 3-month graft loss in B-pos versus B-neg recipients (multivariate logistic regression analysis p = 0.054, 95% confidence interval 0.99-2.85). In conclusion, a B-pos crossmatch in primary and regraft recipients, including a sensitized subset, is predictive of inferior kidney graft outcome.