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BK virus infection after kidney transplantation can negatively impact the prognosis of graft survival. BK nephropathy is an important cause of graft dysfunction and graft loss.Treatment options are limited, and in most cases require immunosuppression reduction.
This study aims to analyze the risk factors associated with BK viruria ,viremia, progression to BK nephropathy and the effect on graft function and survival in isolated and combined kidney transplant recipients.
We retrospectively studied a cohort of isolated and combined kidney transplant recipients at our Institution between 2015-2022. BK viruria was defined as the detection of BKV DNA load in urine ≥10(7) copies /ml and BK viremia as the detection of BKV DNA load in blood ≥10(4) copies/ml. BK nephropathy was diagnosed by positive SV40 staining in biopsy samples.
Donor, recipient and transplant variables were correlated with BK viruria, viremia, nephropathy and graft survival. .Univariate analysis was performed with MedCalc® Statistical Software version 22.014 (MedCalc Software Ltd, Ostend, Belgium; https://www.medcalc.org; 2023)
We performed 473 kidney transplants, between January 2015 and December 2022. 85 patients developed Bk virus infection ( incidence rate 17.9%). Median recipient age was 52 years( range 20-75),57.6 % were females, 15 patients (17.6%) were sensitized. Transplant type was: 88.1% isolated kidney , 3.17% kidney-heart, 2.74% liver-kidney and 5.9% kidney -pancreas. 72,9% had kidneys from deceased donors , mean age was 50 (range 13-71 ). All patients received induction with thymoglobulin (77 patients (90,6%)) or basiliximab (8 patients) and triple immunosuppressive maintenance regimen (steroids + calcineurin inhibitors (IC) + mycofenolic acid). 56 patients (65%) were treated for acute rejection before the diagnosis of BK infection.
25 patients (29.4%) developed BK viruria < 6 post tx month and 60 patients (70.6%) > 6 post tx month. We reduced immunosuppression in 68 patients (79.06%). 43/85 had detectable viremia and 21 patients progressed to Bk nephropathy with graft loss in 15 of those (71.4%).
In univariate analysis, we found a statistically significant difference in creatinine and proteinuria at one year after the diagnosis between patients with or without BK infection: 3.7 vs 1.45 (p < 0.0001), 0.58 vs 0.2 (p < 0.0011), respectively. Reduced immunosuppression was inversely correlated to BK viremia (p <0.0006). BK viremia was correlated to nephropathy ( p < 0.0001) and graft loss (p=0.0005).
The presence of a ureter catheter (p= 0.0268), a BMI > 30 kg/m2 (p=0.046) were correlated with viruria.
In this study, Bk infection was associated with reduced renal function at one year post transplant and graft loss.