Use of Banff 2018 Working Group Classes to Predict Outcomes Versus Use of Baseline Parameters of Renal Function and BK Viremia in BK Virus Nephropathy: A Retrospective Institutional Experience.

OBJECTIVES

To evaluate whether Banff 2018 classification of BK polyomavirus nephropathy better predicts graft outcomes compared with baseline graft function and viremia levels, we correlated clinicopathologic features and morphologic BK polyomavirus nephropathy classes with graft outcomes.

MATERIALS AND

METHODS

We retrospectively analyzed 23 cases of biopsy-proven BK polyomavirus nephropathy over 10 years (2014-2023 ). We stratified biopsy cases into polyoma virus nephropathy class 1, 2, or 3 per the Banff 2018 classification, based on intrarenal viral load (pvl score ) and interstitial fibrosis (ci score ). Outcomes included graft function (serum creatinine, estimated glomerular filtration rate) at 6 and 12 months and graft loss.

RESULTS

Among classes, class 2 was the most common (60.86 % ), followed by class 1 (26.08 % ) and class 3 (13.04 % ). Baseline serum creatinine level, BK viremia, and acute inflammation scores did not differ significantly across classes. Cases classified as class 3 showed significantly worse renal function at 6 and 12 months than cases classified as class 1 and 2 (6-month serum creatinine level of 6.19 ± 3.72, 2.19 ± 0.54, and 2.15 ± 0.95 mg/dL for class 3, 1, and 2, respectively; P < .001 ). Graft loss occurred in 0 of 6 cases with polyoma virus nephropathy class 1, 1 of 14 cases with class 2, and 1 of 3 with class 3. Mortality was observed in 2 of 14 patients with class 2 (14.28% ). Tubular atrophy (ct score ) was significantly higher in class 2 and 3 cases versus class 1 cases (P = .046 ).

CONCLUSIONS

The Banff 2018 polyoma virus nephropathy classification is a robust predictor of graft outcomes. Class 3 was strongly associated with worse renal function and increased graft loss, largely driven by extent of interstitial fibrosis and tubular atrophy. Histopathological assessment is critical for prognostication as viral load alone does not predict outcomes and severity of BK virus nephropathy.