Background: Vascular involvement of the allograft has classically been regarded as a poor prognostic factor in acute kidney graft rejection. Cell-mediated endarteritis often coexists with antibody-mediated rejection. As previous studies reporting the rate of response to treatment have used older versions of the Banff classification, antibody-mediated rejections may have been misclassified as cell-mediated vascular rejections. Our aims were to determine the reversibility of acute rejection episodes according to the Banff 2013 grade and to assess whether clinical responses were associated with histological responses to treatment.

Method: We performed a retrospective cohort study in kidney transplant recipients who were transplanted in 2 Canadian centers between July 2008 and July 2014 and developed at least one episode of acute rejection diagnosed on biopsies performed for a clinical indication. Rejections were graded according to the 2013 Banff classification. A clinical response was defined as a 1 month post-rejection creatinine that had returned within 25% of the best value in the month prior to rejection. A complete histological response was defined as the complete clearance of rejection on a control biopsy performed within 3 months of rejection. The proportions of response with appropriate 95% confidence intervals (CI) are reported. Clinical and histological responses were compared with Fisher exact's tests.

Results: We observed 126 acute rejection episodes in 108 patients. Amongst the 80 borderline, 1A or 1B pure cell-mediated rejections, a clinical response was observed in 77% (95% CI:68-87%) of the episodes. Amongst the 22 episodes of pure cell-mediated Banff grade ≥2 rejection episodes, a clinical response was observed in 73% (95% CI:53-93%) of cases, a figure which fell to 43% (95%CI:22-65%) in the 24 episodes of pure antibody-mediated or mixed rejection episodes (p=0,04). A control biopsy was performed 56±31 days after the initial rejection episode in 50 cases. We did not observe a significant association between clinical and histological responses (p=0,14).

Conclusion: Pure cell-mediated Banff grade ≥2 rejections have a distinct rate of response to treatment when compared to antibody-mediated or mixed acute rejection episodes. Our findings argue for an increased use of control biopsies after an initial rejection episode, as clinical responses do not correlate well with histological responses.

CITATION INFORMATION: Poulin A, Dorais M, Sénécal L, Colette S, Cardinal H. Reversibility of Acute Kidney Rejection According to the Banff 2013 Classification: A Retrospective Cohort Study. Am J Transplant. 2016;16 (suppl 3).

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