Mismatched Blood Types between Donors and Recipients Increase the Risk of BK Viremia One Year after Kidney Transplantation

ABSTRACT Background Kidney transplant recipients are at increased risk for infections such as BK virus, with few treatment options. This study assessed how nonidentical but compatible ABO blood types influence BKPyV‐DNAemia risk. Methods We conducted a retrospective single‐center study from 1/1/2011 to 1/12/2021, focusing on BK viremia (>10 000 copies/mL in two consecutive measurements one week apart) within the first posttransplant year. We used stepwise forward regression for multivariate analysis. Results Of the 1244 transplants, 1084 involved identical blood types. The percentage of living donor grafts was 63.3% (787 cases), with 98.8% (158 cases) in the mismatched blood type group. There were 78 significant BK viremia episodes in the first year, occurring in 5.5% of matched and 11.3% of mismatched blood type recipients (OR 2.16, p = 0.006). For living donors, the viremia rate was 6% overall, with 4.6% in the matched blood type group and 11.4% in the mismatched blood type group (OR 2.22, p = 0.001). Multivariate analysis revealed an increased risk of mismatched blood types in living donor grafts (OR = 2.75, p = 0.002). Conclusions This study revealed an association between blood type mismatch and increased BK viremia in kidney transplant recipients, highlighting a modifiable risk factor for clinicians in organ procurement.