#39 Incidence and outcome of BK virus-associated nephropathy in renal transplant recipients—a single centre experience over fifteen years

Abstract Background and Aims BK virus infection is one of the common clinical problems encountered by transplant physicians. It was estimated that 1–10% of kidney transplant recipients develop BK Virus-Associated Nephropathy (BKVAN). Previous studies were mainly from Europe and the United States. The incidence in the Asian population is less well known. There is no standardised protocol for the treatment of BKVAN. The long-term outcome after diagnosis of BKVAN is also not well defined. This study aimed to look at the incidence and long-term outcome after BKVAN. Method The data from the renal unit of a regional hospital in Hong Kong was reviewed. Cases of biopsy-confirmed BKVAN were identified. Adult renal transplant recipients with renal biopsy done between 1/1/2009 and 31/12/2023 were included. Repeated renal biopsy showing BKVAN was excluded. The total number of renal transplant recipients during the specified period was identified from the Organ Registry and Transplant System. Clinical data, including patient demographics, serum creatinine and immunosuppressants used, were analysed. Death-censored graft survival was analysed by Kaplan–Meier curve. Results A total of 28 cases of biopsy-proven BKVAN were identified. Six were excluded due to recurrent episodes. There were 512 prevalence renal transplant cases during the study period. The incidence of BKVAN was 4.3%. Their baseline characteristics were shown in Table 1. The median time to diagnosis of BKVAN after transplant was 6.3 (3.4–55.2) months (Fig. 1). The median graft survival after diagnosis of BKVAN was 8.3 (6.7–12.3) years. The overall median graft survival for the BKVAN group and the non-BKVAN group was 11.8 (95% CI 6.1–17.5) years and 22.3 (95% CI 18.6–26.1) years, respectively (P = 0.001). (Fig. 2). The immunosuppressants immediately before and after diagnosis of BKVAN were recorded in Table 2. All patients were on prednisolone, but with an overall slight decrease in dose after diagnosis of BKVAN (8.0 ± 5.4 mg vs 7.6 ± 5.7 mg). While majority of patients were on three immunosuppressants regimen (one of which being steroid), one patient was on two immunosuppressants regimen before the diagnosis of BKVAN. Three patients were put on two immunosuppressants regimen after the diagnosis. Two patients were given intravenous immunoglobulin. Conclusion The incidence of BKVAN was 4.3% among renal transplant recipients in our hospital. In patients with BKVAN, graft survival was significantly shortened compared with those who did not develop BKVAN. The treatment for BKVAN was heterogeneous. Further large-scale studies are needed to determine the optimal immunosuppressant regimen after diagnosis of BKVAN to optimise graft survival.