BK-viruria and haemorrhagic cystitis are more frequent in allogeneic haematopoietic stem cell transplant patients receiving full conditioning and unrelated-HLA-mismatched grafts.

The influence of conditioning regimen, donor background and HLA matching on development of BK virus (BKV)-associated haemorrhagic cystitis (HC) was examined in 175 allogeneic haematopoietic stem cell transplant (HSCT) patients, undergoing 179 HSCT events. Twenty-seven patients presented late-onset HC, and BK viruria was verified in 23/27 HC events. Seventy-one (40%) HSCTs were performed with myeloablative conditioning (MC), 108 (60%) were performed with reduced intensity conditioning (RIC), 66 (37%) were performed with a related donor (RD) grafts and 113 (63%) with an unrelated donor (URD) graft. BK viruria was more common during HC, than non-HC events, after MC as compared to RIC (both P<0.001), and with an HLA-mismatched donor (P<0.01). By multivariate logistical regression analysis, independent risk factors for HC were BKV (OR 6.7; 95% CI 2.0-21.7; P=0.001), MC (OR 6.0; 95% CI 2.1-17.3; P<0.001) and URD (OR 3.4; 95% CI 1.1-10.6; P=0.03). However, when analysing HSCT performed with URD or RD grafts separately, BKV (OR 8.5; 95% CI 1.8-19.3; P=0.004) and MC (OR 5.9; 95% CI 1.3-11.3; P=0.009) increased the risk for HC only with a URD, but not with an RD graft.