Assessment of the Banff Working Group classification of definitive BK polyomavirus nephropathy

Abstract

Polyomavirus associated nephropathy (PyVAN) continues to be a burden in renal transplantation leading to allograft insufficiency or graft failure. A presumptive diagnosis of PyVAN is made based on the presence of BK polyomavirus in patients' plasma; however, kidney biopsy remains the gold standard to establish a definitive diagnosis. The Banff Working Group on PyVAN proposed a novel classification of definitive PyVAN based on polyomavirus replication/load level and the extent of interstitial fibrosis. The aim of our study was to test the newly defined classes of PyVAN using independent cohorts of 124 kidney transplant patients with PyVAN with respect to the initial presentation and outcome, and to compare our analysis to that previously reported. Detailed analysis of our cohort revealed that the proposed classification of PyVAN did not stratify or identify patients at increased risk of allograft failure. Specifically, while class 3 was associated with the worst prognosis, there was no significant difference between the outcomes in classes 1 and 2. We also found that the timing posttransplantation and inflammation in areas of interstitial fibrosis and tubular atrophy might be additional factors contributing to an unfavorable allograft outcome in patients with PyVAN.

Classifying Polyomavirus Nephropathy: The “Banff” Initiative

“…Based on statistical analysis, the Banff working group on polyomavirus nephropathy (here referred to as “Banff”) has identified two histologic variables, the ci and pvl scores as predictors of renal function ( 2 , 3 ); those are used in the Banff system to define polyomavirus nephropathy disease classes ( 1 ). Kowalewska et al reported similar observations ( 4 ). They also noted a significantly earlier diagnosis of PyVN in classes 1 and 2 compared to class 3.…”

“…Post diagnosis all studies observed progressive deterioration of renal function in all PyVN classes, most pronounced in disease class 3. Both Banff studies ( 2 , 3 ) and Kowalewska’s report ( 4 ) showed patients in disease class 3 with protracted viral resolution. Vice versa PyVN patients with disease resolution were more often found in disease classes 1 and 2.…”

“…As Kowalewska et al pointed out, their study approach mimicking “…the day-to-day practice” of pathology, is a very valuable contribution confirming some key findings of “Banff.” This day-to-day approach also illustrates that certain disease specific aspects are only uncovered in more rigorous studies. Thus, we interpret Kowalewka’s paper ( 4 ) as complementary to the Banff working group studies and report ( 1 – 3 ).…”

“…All classification systems, especially if newly designed such as the Banff classification of polyomavirus nephropathy (PyVN) ( 1 – 3 ), have to be further validated. In this context, we read, with great interest, the article by Kowalewska et al “ Assessment of the Banff Working Group classification of definitive BK polyomavirus nephropathy ” in the November 2021 issue of Transplant International ( 4 ). We are encouraged to learn about their findings confirming aspects of the Banff 3-tier polyomavirus nephropathy classification system.…”

Current Status, Prevention and Treatment of BK Virus Nephropathy

“…Furthermore, another large study has demonstrated that graft loss in BKVN correlates with 3 clinical parameters only -transplant from a deceased donor, level of BKV viraemia, and the incidence of late AR (52). Multicenter retrospective study of 124 patients with BKVN found no correlation between Banff 2018 classification classes and risk of graft loss (53).…”