Survey of BK virus screening practices by American society of transplantation members

Polyomavirus nephropathy: diagnosis, histologic features, and differentiation from acute rejection

Polyomaviruses, particularly BK virus, are ubiquitous latent infections that may reactivate with immunosuppression during kidney transplantation, resulting in polyomavirus nephropathy (PVN). The levels of viruria and viremia serve as tools for screening and making a presumptive diagnosis of PVN, respectively, while a definitive diagnosis requires a kidney biopsy. There are histologic classifications of PVN based on the extent of tubular cell viral infection, interstitial fibrosis, and interstitial inflammation. These classifications correlate to some degree with graft function and loss, aiding in determining treatment efficacy and prognostication. PVN has histologic overlap with acute cell-mediated rejection, making the differential diagnosis challenging, although there are suggestive features for these different causes of graft dysfunction. This article reviews the diagnosis, histologic findings, and classifications of PVN, and discusses how to differentiate viral nephropathy from acute rejection.

Implementing a regional standardized BK polyomavirus screening protocol across eleven transplant centres

BK polyomavirus (BKPyV) reactivation is regularly monitored after kidney transplant to prevent progression to BK associated nephropathy (BKAN). The New England BK Consortium, made up of 12 transplant centres in the northeastern United States, conducted a quality improvement project to examine adherence to an agreed upon protocol for BKPyV screening for kidney transplants performed in calendar years 2016-2017. In a total of 1047 kidney transplant recipients (KTR) from 11 transplant centres, 204 (19%) had BKPyV infection, defined as detection of BKPyV in plasma, with 41 (4%) KTR progressing to BKAN, defined by either evidence on biopsy tissues or as determined by treating nephrologists. BKPyV infection was treated with reduction of immune suppressants (RIS) in >70% of the patients in all but two centres. There was no graft loss because of BKAN during the two-year follow-up. There were nine cases of post-RIS acute rejection detected during this same period. Adherence to the protocol was low with 54% at 12 months and 38% at 24 months, reflecting challenges of managing transplant patients at all centres. The adherence rate was positively correlated to increased detection of BKPyV infection and was unexpectedly positively correlated to an increase in diagnosis of BKAN.