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

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.