ISN Renal Pathology Working Group Webinar: Towards refinement of the Banff classification system for kidney allograft pathology – addition of activity and chronicity indices

Histological assessment of kidney allograft biopsies, using the Banff classification system,  remains the gold standard to diagnose transplant rejection. Two main Banff categories of rejection are recognized; antibody mediated rejection and T-cell mediated rejection, combined with subcategories designating acute/active, chronic active and chronic forms. Currently, the Banff activity and chronicity indices Working Group has been exploring the development of activity & chronicity indices, which are expected to more accurately reflect active (i.e. responsive to treatment) versus chronic (i.e. unresponsive to treatment) inflammation and fibrosis in the allograft tissue, and might therefore aid treatment decisions in transplant setting.

Learning objectives:

• To review the current Banff kidney transplant rejection classification and its complex subcategories (active, chronic-active, chronic), from the clinical and the pathological perspective.
• To explain the development of activity and chronicity indices based on Banff lesion scores, to simplify the evaluation of rejection activity and chronicity while adding precision.
• To discuss whether this could stratify patients for prognostic and therapeutic decisions
• To illustrate the practical usability of activity and chronicity indices in a case-based discussion.

Further reading:

• Naesens M, Cornell LD, Seshan SV, Haas M. Toward Activity and Chronicity Indices for the Evaluation of Kidney Transplant Rejection: A Viewpoint by the Banff Working Group. Transplantation. 2025;109(6):915-919.
• Haas M, Mirocha J, Huang E, et al. A Banff-based histologic chronicity index is associated with graft loss in patients with a kidney transplant and antibody-mediated rejection. Kidney Int. 2023;103(1): 187-195.
• Vaulet T, Koshy P, Wellekens K, et al. Continuous indices to assess the phenotypic spectrum of kidney transplant rejection. Nat Commun. 2025 ;16(1):10417.