BK virus histopathologic disease severity does not predict allograft outcome in renal transplant recipients

Aims: BK polyomavirus nephropathy (BKPyVN) is an important cause of allograft failure after renal transplantation. Despite early screening for the virus, allograft loss from BKPyVN is still experienced in up to 14% of all renal transplant recipients. The aim of this study was to investigate the association between BKPyVN histopathologic disease severity and allograft outcome at our center. Methods: Kidney transplant recipients who had undergone transplantation between 2002 and 2014 with biopsy proven BKPyVN were eligible for this retrospective study. Each biopsy was re-evaluated by a single pathologist blinded to the clinical data and scored according to the Banff criteria for rejection and BKPyVN. Serum creatinine and BK viral load at the time of biopsy diagnosis as well as allograft outcomes to include allograft survival and serum BK viremia resolution were collected for each recipient to determine if BK virus histopathologic disease severity could predict allograft outcome. Results: Twenty cases of BKPyVN were identified from 1031 total renal transplants performed. There was no statistical association between allograft loss and BKPyVN histopathology (p = 0.49). There was also no statistical association between BKPyVN histopathology and BK viral load at the time of biopsy diagnosis (p = 0.38) or serum BK viremia resolution (p = 0.16). Conclusions: BKPyVN histopathology does not appear to be useful in predicting renal allograft outcome in those recipients diagnosed with BKPyVN which is in contrast to some previously published data.