Clinical Significance of Revised Banff Criteria in the Diagnosis of Antibody-Mediated Rejection

Background: The diagnostic criteria of antibody-mediated rejection (ABMR)has been significantly changed since Banff 2013. The most important revision was adopting microvascular inflammation (MVI)as immunopathologic evidence for ABMR even in C4d-negative cases. In this study, we retrospectively reviewed previous allograft biopsy results and evaluated the impact of this change. Methods: We reviewed results of 536 renal allograft biopsies at Severance Hospital during 2011 to 2013, which were diagnosed according to the Banff 2009 criteria. All biopsy results were reassessed according to the Banff 2017 criteria. Results: According to the Banff 2009 criteria, antibody-mediated changes were observed in 48 cases out of the 536 allograft biopsies (9.0%). According to the Banff 2017 criteria, 28 additional cases (5.2%)were reclassified as antibody-mediated changes. Twenty-six of these cases were C4d-negative ABMR. The most frequent diagnostic finding in these cases was MVI comprising glomerulitis and peritubular capillaritis. Donor-specific antibodies were investigated in 14 of these cases, which revealed positive results in 12 cases. Conclusion: The incidence rate of ABMR has increased after the recent revision of the Banff criteria. The MVI in C4d-negative ABMR cases is the major cause for this increase.