A multicenter application of the 2018 Banff Classification for BK polyomavirus-associated nephropathy in renal transplantation.

Background: With current immunosuppressive regimens, BK polyomavirus-associated nephropathy (BKPyVAN) is still a matter of concern. Stratification of patients at risk for allograft loss is of uttermost importance to guide treatment choice and assess prognosis. In 2018, the Banff working group proposed a classification scheme for the prognosis of BKPyVAN, but external application on independent cohorts is yet to be performed. We investigated how the 2018 Banff classification would perform in a multicenter cohort comprising 50 cases of biopsy-proven BKPyVAN compared to previously published classification systems. Methods: We analyzed consecutive BKPyVAN cases from two Dutch university hospitals between 2002 and 2013, retrieved clinical data, and scored all biopsies according to the Banff 2018 classification, and as a comparison, 4 previously proposed BKPyVAN classification systems. We used estimated glomerular filtration rate trajectories and death-censored graft survival as primary endpoints. Results: The 2018 Banff classification did not associate with estimated glomerular filtration rate decline or graft failure and performed only slightly better than the 4 previously proposed classifiers. Anti-human leukocyte antigen donor-specific antibodies (DSAs), especially in combination with ongoing biopsy-proven BKPyVAN on follow-up, did correlate with graft function and survival. Patients who were DSA+/BKPyVAN+ on follow-up had more inflammation at the baseline biopsy, which by itself was not associated with graft outcomes. Conclusions: Neither the 2018 Banff BKPyVAN classification nor previously published stratification systems could be applied to our multicenter patient cohort. Our data suggest that there might be a prognostic value for follow-up biopsies and DSA measurements to improve risk stratification after BKPyVAN, although prospective multicenter efforts with protocol measurements are needed to confirm this.