BACKGROUND: Recent data suggest that a positive T-cell crossmatch (CM) is associated with reduced post-heart transplant survival in children. An isolated positive B-cell flow crossmatch has been associated with cardiac allograft vasculopathy and worse patient survival in adults. We sought to determine the significance of an isolated positive B-cell crossmatch in pediatric heart transplant recipients.

METHODS: All children less than 21 years of age at transplant with a negative T-cell flow crossmatch and an interpretable B-cell flow crossmatch result between 1999 and 2010 were identified using OPTN data. The primary endpoints were time to first episode of acute rejection, coronary artery disease, and graft loss.

RESULTS: Of 1389 children who met the study inclusion criteria, the median age at transplant was 7 years; 46% were female, 36% had congenital heart disease, 8% were re-transplants, 16% were on VAD support, and 8% had severe renal dysfunction. Overall, 87 children (6%) had a positive B-cell CM at transplant, whereas 1302 (94%) had a negative B-cell CM. During a median follow-up of 7.9 years, and compared to children with a negative B-cell CM, children with an isolated positive B-cell crossmatch had similar freedom from acute rejection (P=0.45), freedom from infection (P=0.66) and freedom from cardiac allograft vasculopathy (P=0.66), which occurred in 18% of subjects by 5 years. Similarly, patient and graft survival were not different between the groups (P=0.44 and 0.55 respectively).

CONCLUSION: In this multi-center transplant registry, an isolated positive B-cell flow crossmatch was found to occur in a small percentage of children undergoing heart transplantation, and appears to be associated with a similar risk of rejection, coronary disease and graft loss compared to children with a negative B-cell and T-cell flow crossmatch. Further research is needed to determine whether differences in patient treatment may account for the findings.

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