Risk Factors for Developing BK Virus-Associated Nephropathy: A Single-Center Retrospective Cohort Study of Kidney Transplant Recipients.

BACKGROUND BK virus (BKV) infection after kidney transplantation leads to BKV-associated nephropathy (BKVAN) in up to 10% of recipients, and is associated with an increased risk of allograft dysfunction or loss. The objective of this study was to estimate the incidence of BKVAN and to analyze whether enhanced induction is associated with an increased risk of BKVAN, possibly justifying more intensive surveillance. MATERIAL AND METHODS This was a single-center retrospective cohort study. All patients who underwent kidney transplantation or simultaneous pancreas and kidney transplantation at the Uppsala University Hospital in Sweden between 2005 and 2014 were included, a period when BKV screening was not yet implemented. The effect of enhanced induction, defined as treatment with thymoglobulin, rituximab, and/or eculizumab, often in combination with IVIg and glycosorb, immunoadsorption and/or plasmapheresis/apheresis, was analyzed in a multivariable Cox proportional hazards model together with sex, age, cytomegalovirus mismatch (donor+/recipient-) and rejection treatment as co-predictors. Further, the effects of BKVAN on graft survival was analyzed in a univariable Cox proportional hazards model. RESULTS In total 44 of 928 (4.7%) patients developed a biopsy-verified BKVAN 4.8 (1.5-34.2) months after transplantation. Male sex was identified as a risk factor (HR 2.02, P=0.04) but not enhanced induction. Patients with BKVAN experienced a significantly higher risk of graft loss (HR 4.37, P<0.001). CONCLUSIONS Male sex, but not enhanced induction, was found to be a risk factor for BKVAN development after kidney transplantation. BKVAN is associated with an increased risk of graft loss.