Clinical Impact of BK Viremia during Haploidentical Stem Cell Transplantation and Its Association with Hemorrhagic Cystitis

Few studies have explored the clinical impact of BK virus DNAemia on haploidentical stem cell transplantation (SCT). Therefore, we retrospectively analyzed the clinical impact of BK DNAemia on haploidentical SCT between 2021 and 2023. In total, 278 patients were enrolled. BKV DNA in plasma was positive in 54 (19.4%) patients, the median time to onset was 35 days (range, 12–385) after transplantation, and the median blood BK viral load was 4970 copies/ml (191-5.04E + 9). The incidence of hemorrhagic cystitis (HC), including severe cases, was significantly higher in the BK-positive group compared to the BK-negative patients (77.8% vs. 20.5%, P < 0.001; 27.8% vs. 10.3%, P < 0.001). Receiver operating characteristic curve analysis revealed that a blood BKV-DNA load > 0 copies/ml had a sensitivity of 47.13% and a specificity of 93.68% for predicting HC (P < 0.0001). A BKV-DNA load > 191 copies/ml exhibited a sensitivity of 60.53% and a specificity of 87.87% for predicting severe HC (P < 0.0001). BK viremia is prevalent among haploidentical transplant recipients. Moreover, these findings suggest that BK viremia serves as an early indicator of HC development.