Background: Diagnostic criteria for antibody-mediated rejection (AMR) of the cardiac allograft have recently been proposed as part of the International Society for Heart and Lung Transplantation (ISHLT) biopsy grading scheme. Histologic features of vascular adherence of macrophages (VASC) and endothelial activation or swelling in capillaries (ENDO) are proposed as criteria to prompt the immunohistochemical investigation of biopsies for AMR. The aim of this study was to determine whether VASC and ENDO are adequate to act as screening parameters to trigger further AMR investigation.
Methods: We examined our database of biopsy findings where histologic vascular parameters as well as immunofluorescence (IF) to detect AMR were collected (n = 3,170). Histologic parameters were graded semi-quantitatively on a scale from 1 to 5, where 1 = absence and 5 = obvious and generalized presence of the finding.
Results: Seven hundred sixty-eight of 3,170 biopsies had IF findings diagnostic of AMR in the absence of cellular rejection (ISHLT = 0). ENDO had a sensitivity of 63% and a specificity of 80%. VASC had a sensitivity of 30% and specificity of 99%. Combining the interpretation of the 2 tests did not result in a significant improvement of test sensitivity.
Conclusions: Neither ENDO, VASC nor the combination of the tests indicated sufficiently high sensitivity to serve as a screening tool before further diagnostic investigation for AMR. Immunohistochemical testing remains necessary in the majority of cases to identify AMR.