In kidney transplant recipients with BK polyomavirus infection, early BK nephropathy, microvascular inflammation, and serum creatinine are risk factors for graft loss

Background Little information is available on the risk factors for graft loss in kidney transplant recipients with BK polyomavirus ( BKP yV) nephropathy ( BKVN ) in the presence or absence of antibody‐mediated rejection ( AMR ). Methods We examined the risk factors for graft loss in consecutive kidney allograft recipients with biopsy‐confirmed BKVN , with or without concomitant AMR . Results A total of 1904 kidney transplants were performed at our institution during 2005–2011. Of these, 330 (17.33%) were diagnosed with BKP yV viremia, and 69 were diagnosed with BKVN (3.6%). Eleven patients had a concomitant diagnosis of AMR . Patients with AMR were characterized by significantly higher peak panel‐reactive antibody, retransplant rates, and desensitization preconditioning at the time of transplantation, as well as microvascular inflammation ( MVI = glomerulitis + peritubular capillaritis), C4d score, and donor‐specific antibody at the time of diagnosis ( P ≤ 0.01). Treatment with plasma exchange, intravenous immunoglobulin, and cidofovir was more prevalent in this group ( P ≤ 0.02). Univariate analyses assessing the risk factors for graft loss in all patients with BKVN , identified an independent association of African‐American race, deceased‐donor transplantation, serum creatinine (Scr), MVI , and early disease ( BKVN within 6 months of transplant) with poor outcomes. Multivariate analyses retained only 3 variables: Scr >2 mg/dL (hazard ratio [ HR ] = 4.3, 95% confidence interval [ CI ] 1.9–9.7, P = 0.0004), early BKVN ( HR = 2.7, 95% CI 1.3–5.3, P = 0.004), and MVI ( HR = 1.8, 95% CI 1.2–2.8, P = 0.008). Conclusions These observations suggest that, in patients with BK infection, early BKVN , Scr >2, and MVI are predictors of poor outcomes. Further studies are needed to determine effective treatment strategies for BKVN , with or without AMR .