OBJECTIVETo investigate the optimal time window for intervention of BK virus (BKV) replication and its effect on the outcomes of kidney transplant recipients (KTRs).

METHODSA retrospective analysis of the clinical data and treatment regimens was conducted among KTRs whose urine BKV load was ≥1.0×10copies/mL following the operation between April, 2000 and April, 2015. KTRs with urine BKV load <1.0×10copies/mL matched for transplantation time served as the control group.

RESULTSA total of 54 recipients positive for urine BKV were included in the analysis. According to urine BKV load, the recipients were divided into 3 groups: group A with urine BKV load of 1.0×10-1.0×10copies/mL (n=22), group B with urine BKV load >1.0×10copies/mL (n=24), and group C with plasma BKV load ≥1.0×10copies/mL (n=8); 47 recipients were included in the control group. During the follow-up for 3.2-34.5 months, the urine and plasma BKV load was obviously lowered after intervention in all the 54 BKV-positive recipients (P<0.05). Eighteen (81.82%) of the recipients in group A and 19 (79.17%) in group B showed stable or improved estimated glomerular filtration rate (eGFR) after the intervention; in group C, 4 recipients (50%) showed stable eGFR after the intervention. In the last follow-up, the recipients in groups A and B showed similar eGFR with the control group (P>0.05), but in group C, eGFR was significantly lower than that of the control group (P=0.001). The recipients in group A and the control group had the best allograft outcome with stable or improved eGFR.

CONCLUSIONEarly intervention of BKV replication (urine BKV load ≥1.0×10copies/mL) in KTRs with appropriate immunosuppression reduction can be helpful for stabilizing the allograft function and improving the long-term outcomes.