607 Which T-Cell Crossmatch Method Best Predicts Allograft Loss in Pediatric Heart Transplant Recipients?

Abstract

Purpose: Several methods are currently available for performing a T-cell crossmatch (CM). No national cohort studies have explored the relationship between T-cell CM, CM methodology, and allograft survival after pediatric heart transplantation. Methods and Materials: All children 18 years old transplanted between 1/1999 and 12/2010 with an interpretable T-cell CM result, either by compliment dependent cytotoxicity (CDC) or flow cytometry, were identified using OPTN data. Children with a CDC-positive CM (N 83) and those with a CDC-neg/flow-pos CM (N 37) were compared with CDCneg/flow-neg controls (N 1225). Cox proportional hazard analysis was used to identify multivariable risk factors for time to graft loss. Results: During the past decade, utilization of CDC-CM has decreased significantly whereas the use of flow CM has increased (both P 0.01). Currently 1 in 10 pediatric heart transplants are performed in the context of a positive T-cell CM. Compared to CDC-neg/flow-neg controls, patients with a CDC-pos CM were more likely to be listed UNOS status 1A, have a pre-transplant diagnosis of congenital heart disease or re-transplant, and have a positive PRA (both class I and II). Utilization of pre-transplant mechanical circulatory support was not associated with CM result. CDCpos CM was associated with an increased prevalence of treated allograft rejection by 1 year compared to CDC-neg/flow-pos patients and CMnegative patients (48% vs. 19% and 23%; P 0.001). In multivariable analysis, patients with a CDC-pos CM were more likely to have graft loss than controls (HR 1.9; CI 1.3-2.6) while those with a CDC-neg/flow-neg CM did not show increased risk (HR 0.9; CI 0.4-2.0). Conclusions: Amongst a population of pediatric heart transplant recipients, CDC-pos T-cell CM was strongly associated with an increased risk of death or allograft loss. While the utilization of flow based assays has become more common, a positive flow CM may perform less well in identifying patients at risk for graft loss than the traditional CDC method.