Antibody-mediated rejection in the Banff classifications of 2007 and 2017: A comparison of renal graft loss prediction capability.

BACKGROUND: Antibody-mediated rejection (ABMR) is the leading cause of kidney graft loss worldwide. Criteria for acute humoral rejection (currently labeled active humoral rejection) established by the 2007 Banff classification are highly specific but lack sensitivity. Modifications to the Banff classification were introduced for its 2013 and 2017 versions in order to identify more cases of this entity.

PURPOSE: We intend to demonstrate that, compared to its 2007 version, the 2017 Banff classification bears an improved capacity for graft loss prediction when histologic criteria for active ABMR are met.

PATIENTS AND METHODS: Single-center retrospective cohort study. A random sample of 201 kidney recipients who underwent a graft biopsy since January 2004 was analyzed. Patients were classified as ever developing histologic characteristics of acute ABMR (2007 Banff) or not and renal survival between groups was compared. The same patients were then classified as ever developing histologic characteristics of active ABMR (2017 Banff) or not and renal survival was again compared. Presence of circulating donor-specific antibodies (DSA) was not taken into consideration.

RESULTS: Patients were followed for a median 13.9 ± 7.9 years, during which grafts were biopsied on 537 occasions (2.7 ± 1.6 biopsies per graft). Baseline eGFR was 73.26 ± 17.6 ml/min and baseline creatinine 1.14 ± 0.25 mg/dl. Graft loss occurred in 38 recipients (18.9%) mainly due to ABMR (60.5%). Acute ABMR (2007 Banff) was identified in 11 recipients (5.5%) and graft survival did not differ between groups with and without active ABMR occurrence (log-rank p = 0.939). Active ABMR (2017 Banff) was found in 59 recipients (29%) and graft survival was better from the second post-transplant year onward in the group of patients without active ABMR occurrence (log-rank p = 0.001). Moderate microvascular inflammation was present in 89.6% of the 48 additional patients with active ABMR.

CONCLUSION: The 2017 Banff classification identifies more patients who develop active ABMR and stratifies graft loss risk better than the 2007 version.