#2082 Effectiveness of a surveillance protocol and early mTORi conversion according to Urine BK viral load in Thai kidney transplant recipients

Abstract Background and Aims BK viral nephropathy (BKVN) is a crucial cause of early kidney allograft failure. Early detection and prompt treatment in the case of a high urine viral load might be more advantageous than waiting until BK viremia occurs. Data regarding outcome of BK infection based on adjustments of immunosuppression according to urine viral load is limited. Method A prospective cohort study of kidney transplant (KT) recipients at Siriraj Hospital, conducted between January 2015 and June 2020, involved monitoring urine BK viral load (RT-PCR) at 1, 2, 3, 6, 12, 18, and 24 months after KT. Determination of BK viremia and adjustments to immunosuppression were performed in patients with urine BK viral loads exceeding 1,000,000 copies/ml or demonstrating progressive increments in BK viruria. Initially, mycophenolate (MPA) dosage was reduced, and subsequently, conversion to mTOR inhibitors was considered for non-responsive cases. Data on the overall incidence and risk factors of BK viremia and/or BKVN were collected. Results Out of a total of 339 enrolled patients, 234 (69%) underwent deceased KT, and 49 (14.5%) received induction therapy with anti-thymocyte globulin. The incidence of BK viruria, viremia, and BKVN were 38.6% (131 patients), 9.7% (33 patients), and 4.1% (14 patients), respectively. The median time of occurrence for BK viruria and BKVN was 3 (IQR 1-12) and 4.5 (IQR 3–18) months after KT, respectively. Most BKVN cases (71.4%) developed within the first six months post KT. We did not find any significant risk factors associated with the occurrence of BK viremia or BKVN. Regarding the adjustment of immunosuppression, the initial reduction of MPA dosage was effective in 48 out of 92 patients (52.17%). In cases with an extremely high urine BK viral load or no response to MPA reduction, 46 patients received a change from MPA to everolimus, which was successful in 38 patients (82.6%). No graft loss due to BKVN was observed throughout the study. Conclusion The incidence of BK infection after KT in Thai recipients is high, comparable to western population. A surveillance protocol with urine BK viral load and early mTORi conversion is effective for prevention of allograft loss from BKVN.