Utility of post-transplant anti-HLA antibody measurements in pediatric cardiac transplant recipients

Background: Studies have associated anti-HLA antibodies detected by panel-reactive antibody (PRA) with increased risk for rejection and transplant coronary artery disease (TCAD) in adults, but the role of PRAs in monitoring immunologic status after pediatric cardiac transplantation has not been described. Methods: We reviewed post-transplant PRAs in 96 pediatric heart recipients. PRAs were performed concurrently with endomyocardial biopsy and if rejection was suspected. The presence of anti-HLA IgG antibodies was defined as >10% reactivity. Pre-transplant variables, including age, race, gender, pre-transplant PRAs and presence of a mechanical assist device, were correlated with post-transplant PRAs. Outcome variables included rejection history, TCAD incidence and survival. Results: The mean age of patients was 9.0 ± 6.8 years. A mean of 8.1 ± 5.3 PRAs were measured over a follow-up period of 4.8 ± 2.7 years. There was a mean of 0.55 ± 0.71 rejection events per patient-year, and TCAD was detected in 19 (22%) patients. Nineteen patients (20%) had anti-HLA Class I antibodies and 37 (39%) had Class II antibodies detected after transplant. There was no association between Class I antibodies and survival, TCAD or rejection. Class II antibodies were associated with worse survival and a decreased time-free of TCAD. Class II antibodies were also associated with rejection at the time of measurement (sensitivity 17%, specificity 94%) and for the ensuing 3 months (sensitivity 12%, specificity 94%). Conclusions: Class II anti-HLA antibodies correlate with worse patient outcomes and rejection episodes after pediatric cardiac transplant. A low sensitivity precludes use as a sole diagnostic tool, but post-transplant PRAs may be an important adjunct in a multi-faceted algorithm to assess immunologic status.