Pretransplantation Risk Stratification for BK Polyomavirus DNAemia After Kidney Transplantation: Impact of Donor Viruria, Anti‐BKPyV IgG Antibodies, and Viral Subtype

ABSTRACT Background BK polyomavirus (BKPyV) DNAemia is a major complication of kidney transplantation and can progress to BKPyV‐associated nephropathy. In the absence of effective antiviral therapies, pretransplant risk stratification is essential. We evaluated the utility of pretransplant virological and serological markers for identifying recipients at risk for posttransplant BKPyV DNAemia. Methods This retrospective single‐center cohort study included 111 living donor–recipient pairs who underwent kidney transplantation between 2016 and 2023 and had available pretransplant urine and serum samples. Urinary BKPyV‐DNA levels were quantified by PCR, anti‐BKPyV VP1 IgG levels were measured by ELISA, and viral subtypes were determined by VP1 sequencing. ROC‐derived cutoff values were used to construct combined risk models. Results: BKPyV DNAemia developed in 18 recipients. Pretransplant donor viruria (> 130 copies/mL) and higher donor anti‐BKPyV IgG levels (> 5.27) were associated with subsequent DNAemia. The incidence of DNAemia was higher among recipients with lower anti‐BKPyV IgG levels (≤ 1.82). Recipients with low antibody levels receiving grafts from donors with high viruria had the highest incidence of DNAemia (62.5%). BKPyV subtype III was detected in 7 of 18 recipients (38.9%) during posttransplant DNAemia despite its rare detection before transplantation. Conclusions A pretransplant risk stratification model combining donor urinary BKPyV‐DNA and recipient anti‐BKPyV IgG identified a subgroup at increased risk for posttransplant BKPyV DNAemia in this single‐center cohort. Although external validation is required, this simple two‐factor approach may facilitate risk‐adapted surveillance after kidney transplantation.