Positive serum crossmatch as predictor for graft failure in HLA-mismatched allogeneic blood stem cell transplantation

Background. Evaluation of patient sera for complement-fixing anti-donor antibodies (serum crossmatch [XM]) before allogeneic blood stem cell transplantation (BSCT) is routine in most centers. However, in contrast to kidney transplantation, the predictive value of a positive XM for outcome of BSCT is still unclear, and a positive XM is presently not regarded as an absolute contraindication to proceed to transplant. Methods. To clarify the role of a positive XM as predictor for overall survival (OS) and graft failure (GF) after BSCT, a retrospective, single-center, matched-pair analysis was performed. Enrolled were all NM-positive BSCT performed at our institution from 1985 to 2000 (n=30). Controls (n=30) were matched for disease, disease stage, patient age, period of transplant, conditioning regimen, protocol for prevention of graft-versus-host disease, and type of donor (related vs. unrelated, HI-A-identical vs. HLA-mismatched). Results. Multivariate statistical analysis of all enrolled 60 transplants revealed GF as the all-dominating, independent risk factors for low OS (relative risk [RR]: 59.5, P<0.0001). Univariate (Kaplan-Meier) analysis could attribute inferior OS and high incidence of GF to the subgroup of HLA-mismatched, NM-positive transplants (P=0.01). Conclusions. A XM should always be performed in patients awaiting a BSCT from HLA-mismatched donors, because a positive XM is a predictor for inferior OS due to GF in BSCT.