The 2018 Banff Working Group Classification of Definitive Polyomavirus Nephropathy: A Multi Center Validation Study in the Modern Era

Polyomavirus nephropathy (PVN) remained inadequately classified until 2018 when the "Banff Working Group" published a new 3-tier morphologic classification scheme derived from in-depth statistical analysis of a large multinational patient cohort. Here we report a multicenter "modern era" validation study that included 99 patients with definitive PVN transplanted post 1/1/2009 and followed the original 2018 study design. Results validate the PVN classification, i.e. the three PVN disease classes predicted clinical presentation, allograft function and outcome independent of therapeutic intervention. PVN class 1 compared to classes 2 and 3 was diagnosed earlier (16.9 weeks post transplantation (median), P=0.004), and showed significantly better function at 24-months post-index biopsy (S-Cr 1.75 mg/dl, geometric mean, versus class 2: P=0.037, versus class 3: P=0.013). Class 1 presented during long-term follow-up with a low graft failure rate: 5% class 1, versus 30% class 2, versus 50% class 3 (P=0.009). Persistent PVN was associated with an increased risk for graft failure (and functional decline in class 2 at 24-months post diagnosis; S-Cr with persistence: 2.48 mg/dl versus 1.65 with clearance, geometric means, P=0.018). In conclusion, we validate the 2018 Banff Working Group PVN classification that provides significant clinical information and enhances comparative data analysis.