Survey of North American pathologist practices regarding antibody-mediated rejection in cardiac transplant biopsies

Background: The 2004 International Society for Heart and Lung Transplantation consensus report specified an entity of histopathologic antibody-mediated rejection (hAMR) but did not define specific histologic criteria. Therefore, there is no gold standard for hAMR diagnosis. Methods: In May 2009 we performed a survey of pathologists from cardiac transplant centers in the United States and Canada assessing practices regarding hAMR investigation. Results: Of 94 centers who responded to our survey (77% response rate), 90% reported investigating for hAMR, and 80% of those reported having a defined protocol. Of centers with a defined protocol, 23% investigated all biopsies for hAMR. Of those who investigated for hAMR selectively, the most common triggers were clinical suspicion (61%) or suggestive histologic findings (36%). Sixteen different stains were used for hAMR investigation, the most common being C4d by immunofluorescence (38%), immunohistochemistry (38%) or both (21%). Conclusions: We found wide variation in pathologists' practices regarding hAMR diagnosis. A consensus document regarding hAMR is needed to better align our collective protocols, understand this disease process and to optimize patient care.